O-acetylcarnitine

O-acetylcarnitine (as-e-til-kar′ni-ten)

The acetyl derivative of carnitine formed by carnitine acetyltransferase. Facilitates acetyl transport into the mitochondria and is an important fuel source for sperm.

o-aminobenzoic acid
o-aminobenzoic acid (a-me′no-ben-zo′ik)

SYN: anthranilic acid.

o-chlorobenzalmalononitrile
o-chlorobenzalmalononitrile (or′tho-klor′o-ben-zal-ma-lon′o-ni-tril)

A strong lacrimator used in riot control.

o-chlorophenol
o-chlorophenol

An antiseptic liquid, used in the treatment of lupus.

o-diphenolase
o-diphenolase (di-fen′o-las)

SYN: catechol oxidase.

Ω
Ω

1. The 24th and last letter of the Greek alphabet, omega. 2. Symbol for ohm.

O
O

1. Symbol for oxygen; orotidine. 2. Abbreviation for opening (in formulas for electrical reactions). 3. Symbol for a blood group in the ABO system. See ABO blood group, Blood Groups appendix. 4. An abbreviation derived from ohne Hauch (without a film), used as a designation for: 1) antigens that occur in the bacterial cell, in contrast to those in the flagella; 2) specific antibodies for such somatic antigens; 3) the agglutinative reaction between somatic antigen and its antibody.

15O
¹⁵O

Symbol for oxygen-15.

16O
¹⁶O

Symbol for oxygen-16.

17O
¹⁷O

Symbol for oxygen-17.

18O
¹⁸O

Symbol for oxygen-18.

o- o-

In chemistry, the abbreviation for ortho- (2).

OA
OA

Abbreviation for occipitoanterior position.

oak apple
oak apple

SYN: nutgall.

oari- oari-, oario-

Obsolete term for an ovary. See oo-, oophor-, ovario-. [G. oarion, a small egg, dim. of oon, egg]

oath
oath (oth)

A solemn affirmation or attestation.

OB
OB

Abbreviation for obstetrics.

O'Beirne
O'Beirne

James, Irish surgeon, 1786–1862. See O. sphincter.

obeliac
obeliac (o-be′le-ak)

Relating to the obelion.

obeliad
obeliad (o-be′le-ad)

Toward the obelion.

obelion
obelion (o-be′le-on)

A craniometric point on the sagittal suture between the parietal foramina near the lambdoid suture. [G. obelos, a spit]

Obermayer
Obermayer

Friedrich, Austrian physician, 1861–1925. See O. test.

Obermeier
Obermeier

Otto H.F., German physician, 1843–1873. See O. spirillum.

Obersteiner
Obersteiner

Heinrich, Austrian neurologist, 1847–1922. See O.-Redlich line, O.-Redlich zone.

obese
obese (o-bes′)

Excessively fat. SYN: corpulent. [L. obesus, fat, partic. adj., fr. ob-edo, pp. -esus, to eat away, devour]

obesity
obesity (o-be′si-te)

An excess of subcutaneous fat in proportion to lean body mass. Excess fat accumulation is associated with increase in the size (hypertrophy) as well as the number (hyperplasia) of adipose tissue cells. O. is variously defined in terms of absolute weight, weight-height ratio, distribution of subcutaneous fat, and societal and esthetic norms. Measures of weight in proportion to height include relative weight (RW, body weight divided by median desirable weight for a person of the same height and medium frame according to actuarial tables), body mass index (BMI, kg/m²) and ponderal index (kg/m³). These do not differentiate between excess adiposity and increased lean body mass. In contrast, subscapular and triceps skinfold measurements and determination of the waist-to-hip ratio help define the regional deposition of fat and differentiate the more medically significant central o. from peripheral o. in adults. No single cause can explain all cases of o.. Ultimately it results from an imbalance between energy intake and energy expenditure. While faulty eating habits related to failure of normal satiety feedback mechanisms may be responsible for some cases, many obese persons neither consume more calories nor eat different proportions of foodstuffs than nonobese persons. Contrary to popular belief, o. is not caused by disorders of pituitary, thyroid, or adrenal gland metabolism. However, it is often associated with hyperinsulinism and relative insulin resistance. Studies of obese twins strongly suggest the presence of genetic influences on resting metabolic rate, feeding behavior, changes in energy expenditures in response to overfeeding, lipoprotein lipase activity, and basal rate of lipolysis. Environmental factors associated with o. include socioeconomic status, race, region of residence, season, urban living, and being part of a smaller family. The prevalence of o. is greater when weight is measured during winter rather than summer. O. is much commoner in the northeastern and midwestern U.S. than in the south and west, a phenomenon independent of race, population density, and season. SYN: adiposity (1) , corpulence, corpulency. [L. obesus, pp. of obedo, to eat up, + -ity] O. is a major public health problem and the leading nutritional disorder in the U.S. A widely accepted definition of o. is body weight that is 20% or more in excess of ideal weight-for-height according to actuarial tables. By this definition, 34% of adults in the U.S. are obese, and there is evidence that the prevalence of o. is increasing in both children and adults. The National Institutes of Health have defined o. as a BMI of 30 kg/m² or more, and overweight as a BMI between 25–30 kg/m². By these criteria, 55% of adults are either overweight or obese. O. is an independent risk factor for hypertension, hypercholesterolemia, type 2 diabetes mellitus, myocardial infarction, certain malignancies (cancer of the colon, rectum, and prostate in men and of the breast, cervix, endometrium, and ovary in women), obstructive sleep apnea, hypoventilation syndrome, osteoarthritis and other orthopedic disorders, infertility, lower extremity venous stasis disease, gastroesophageal reflux disease, and urinary stress incontinence. Lesser degrees of o. can constitute a significant health hazard in the presence of diabetes mellitus, hypertension, heart disease, or their associated risk factors. Body fat distribution in central (abdominal or male pattern, with an increased waist-to-hip ratio) versus peripheral (gluteal or female pattern) adipose tissue deposit is associated with higher risks of many of these disorders. Obese persons are more liable to injury, more difficult to examine by palpation and imaging techniques, and more likely to have unsuccessful outcomes and complications from surgical operations. Not least among the adverse effects of o. are social stigmatization, poor self-image, and psychological stress. Weight reduction is associated with improvement in most of the health risks of o.. All treatments for o. (other than cosmetic surgical procedures in which subcutaneous fat is mechanically removed) require creation of an energy deficit by reducing caloric intake, increasing physical exercise, or both. Basic weight-reduction programs involve consumption of a restricted-calorie, low-fat diet and performance of at least 30 minutes of endurance-type physical activity of at least moderate intensity on most and preferably all days of the week. Behavior modification therapy, hypnosis, anorexiant drugs, and surgical procedures to reduce gastric capacity or intestinal absorption of nutrients are useful in selected cases, but the emphasis should be on establishing permanent changes in lifestyle. Weight reduction is not recommended during pregnancy or in patients with osteoporosis, cholelithiasis, severe mental illness including anorexia nervosa, or terminal illness.
android o. central o. (apple shape) with fat excess primarily in abdominal wall and visceral mesentery; associated with glucose intolerance, diabetes, decreased sex hormone–binding globulin, increased levels of free testosterone, and increased cardiovascular risk.
gynecoid o. o. with fat excess mainly in the femoral-gluteal region (pear shape).
hypothalamic o. o. caused by disease of the hypothalamus.
hypothalamic o. with hypogonadism SYN: adiposogenital dystrophy.
morbid o. o. sufficient to prevent normal activity or physiologic function, or to cause the onset of a pathologic condition.
simple o. o. resulting when caloric intake exceeds energy expenditure.

obex
obex (o′beks) [TA]

The point on the midline of the dorsal surface of the medulla oblongata that marks the caudal angle of the rhomboid fossa or fourth ventricle. It corresponds to a small, transverse medullary fold overhanging the calamus scriptorius. [L. barrier]

obfuscation
obfuscation (ob-fus-ka′shun)

1. A rendering dark or obscure. 2. A deliberate attempt to confuse or to prevent understanding. [L. ob-fusco, pp. -atus, to darken, fr. fuscus, dark, tawny]

OB/GYN
OB/GYN

Abbreviation for obstetrics and gynecology.

obidoxime chloride
obidoxime chloride (ob′e-dok-sem)

A cholinesterase reactivator much like 2-PAM.

object
object (ob′jekt)

1. Anything to which thought or action is directed. 2. In psychoanalysis, that through which an instinct can achieve its aim. 3. In psychoanalysis, often used synonymously with person.
good o. in psychoanalysis, the good or supporting aspects of an important person in the patient's life, especially of a parent or parent-surrogate.
sex o. a person toward whom another is sexually attracted; a term most used by a female to indicate that a male narrowly views her as a vehicle for sex while completely disregarding the rest of her persona.
test o. 1. an o. having very fine surface markings, mounted on a slide, used to determine the defining power of the objective lens of a microscope; 2. the target in measurement of the visual field.
transitional o. an o. used by many children as a substitute for a parent who is absent (usually temporarily) to help them deal with separation; typically, a blanket or stuffed toy.

object choice
object choice

In psychoanalysis, the object (usually a person) upon which psychic energy is centered.

objective
objective (ob-jek′tiv)

1. The lens or lenses in the object end of the body tube of a microscope, by means of which the rays coming from the object examined are brought to a focus. SYN: object glass. 2. Viewing events or phenomena as they exist in the external world, impersonally, or in an unprejudiced way; open to observation by oneself and by others. Cf.:subjective. [L. ob- jicio, pp. -jectus, to throw before]
achromatic o. an o. that is corrected for two colors chromatically, and one color spherically.
apochromatic o. an o. in which chromatic aberration is corrected for three colors and spherical aberration is corrected for two.
immersion o. a high power o. used with a drop of oil between the lens and the specimen on the slide, allowing a greater numerical aperture; similar lenses are available for use with water as the immersing liquid.

objective assessment data
objective assessment data

Those facts that are observable and measurable by the nurse.

obligate
obligate (ob′li-gat)

Without an alternative system or pathway. [L. ob-ligo, pp. -atus, to bind to]

oblique
oblique (ob-lek′)

Slanting; deviating from the perpendicular, horizontal, sagittal, or coronal plane of the body. In radiography, a projection that is neither frontal nor lateral. [L. obliquus]

obliquity
obliquity (ob-lik′wi-te)

SYN: asynclitism.
Litzmann o. inclination of the fetal head so that the biparietal diameter is oblique in relation to the plane of the pelvic brim, the posterior parietal bone presenting to the parturient canal. SYN: posterior asynclitism.
Nägele o. inclination of the fetal head in cases of flat pelvis, so that the biparietal diameter is oblique in relation to the plane of the pelvic brim, the anterior parietal bone presenting to the parturient canal. SYN: anterior asynclitism.

obliquus
obliquus (ob-li′kwus)

Denoting a structure having an oblique course or direction; a name given, with further qualification, to several muscles. See muscle. [L. slanting, oblique]

obliteration
obliteration (ob-lit-er-a′shun)

Blotting out, especially by filling of a natural space or lumen by fibrosis or inflammation. In radiology, disappearance of the contour of an organ when the adjacent tissue has the same x-ray absorption. See silhouette sign of Felson. [L. oblittero, to blot out]
osteoplastic o. of the frontal sinus operation to remove the diseased contents, including the mucous membrane, of the frontal sinus and to obliterate the sinus with a free fat graft without altering the external contour of the sinus.

oblongata
oblongata (ob-long-gah′ta)

SYN: medulla o.. [L. fem. of oblongatus, from oblongus, rather long]

obnubilation
obnubilation (ab-noo′bil-a′shun)

A clouded mental state. [L. ob-nubilo, to becloud, obscure, fr. nubes, cloud]

OBS
OBS

Abbreviation for organic brain syndrome.

observer
observer (ob-zer′ver)

One who perceives, notices, or watches; in behavioral research with humans, the investigator or his/her surrogate. [L. observo, to watch]
nonparticipant o. an investigator who studies a group of subjects engaged in certain activities but does not directly participate in these activities, presumably being able to study them more objectively.
participant o. an investigator who while studying the activities of a group of subjects also participates in their activities, presumably being able to gain more detailed, relevant information but with less objectivity.

obsession
obsession (ob-sesh′un)

A recurrent and persistent idea, thought, or impulse to carry out an act that is ego-dystonic, that is experienced as senseless or repugnant, and that the individual cannot voluntarily suppress. [L. obsideo, pp. -sessus, to besiege, fr. sedeo, to sit]
impulsive o. an o. accompanied by action, sometimes becoming a mania.
inhibitory o. an o. involving an impediment to action, usually representing a phobia.

obsessive-compulsive
obsessive-compulsive

Having a tendency to perform certain repetitive acts or ritualistic behavior to relieve anxiety, as in o. neurosis ( e.g., a compulsive, ritualistic need to wash one's hands many dozens of times per day).

obsolescence
obsolescence (ob-so-les′ens)

Falling into disuse; denoting the abolition of a function. [L. obsolesco, to grow out of use]

obstetric
obstetric, obstetrical (ob-stet′rik, -ri-kal)

Relating to obstetrics.

obstetrician
obstetrician (ob-ste-tri-sh′un)

A physician specializing in the medical care of women during pregnancy and childbirth. [see obstetrics]

obstetrics
obstetrics (OB) (ob-stet′riks)

The specialty of medicine concerned with the care of women during pregnancy, parturition, and the puerperium. SYN: tocology. [L. obstetrix, a midwife, fr. ob-sto, to stand before, denoting the position formerly taken by the midwife]

obstinate
obstinate (ob′sti-nat)

1. Firmly adhering to one's own purpose or opinion, even when wrong; not yielding to argument, persuasion, or entreaty. SYN: intractable (2) , refractory (2) . 2. SYN: refractory (1) . [L. obstinatus, determined]

obstipation
obstipation (ob-sti-pa′shun)

Intestinal obstruction; severe constipation. [L. ob, against, + stipo, pp. -atus, to crowd]

obstruction
obstruction (ob-struk′shun)

Blockage, clogging, or impeded flow, e.g., by occlusion or stenosis. [L. obstructio]
closed loop o. o. of a segment of intestine either rotated on a fixed point (volvulus) or herniated through a fibrous opening (as under an adhesion or into a hernia); frequently associated with impaired perfusion ultimately resulting in gangrene.
ureteropelvic junction o. an impediment to drainage of urine from kidney usually due to partial or intermittent blockage of renal collecting system at the junction of renal pelvis and ureter.
ureterovesical o. o. of the lower ureter at its entrance into the bladder.

obstruent
obstruent (ob′stroo-ent)

1. Rarely used term for obstructing or clogging. 2. Rarely used term for an agent that obstructs or prevents a normal discharge, especially a discharge from the bowels. [L. obstruo, to build against, obstruct]

obtund
obtund (ob-tund′)

To dull or blunt, especially to blunt sensation or deaden pain. [L. ob-tundo, pp. -tusus, to beat against, blunt]

obturation
obturation (ob-too-ra′shun)

Obstruction or occlusion. [see obturator]
intermittent self-o. passage of a blunt object in a lumen or meatus to occlude it or to dilate it.

obturator
obturator (ob′too-ra-tor)

1. Any structure that occludes an opening. 2. Denoting the o. foramen, the o. membrane, or any of several parts in relation to this foramen. 3. A prosthesis used to close an opening of the hard palate, usually a cleft palate. 4. The stylus or removable plug used during the insertion of many tubular instruments. [L. obturo, pp. -atus, to occlude or stop up]

obtuse
obtuse (ob-toos′)

1. Dull in intellect; of slow understanding. 2. Blunt; not acute. [see obtund]

obtusion
obtusion (ob-too′zhun)

1. Dullness of sensibility. 2. A dulling or deadening of sensibility.

Occam's razor
Occam's razor

The principle of scientific parsimony. William of Occam (14th century) stated it thus: “The assumptions introduced to explain a thing must not be multiplied beyond necessity.”

occipital
occipital (ok-sip′i-tal)

Relating to the occiput; referring to the o. bone or to the back of the head. SYN: occipitalis.

occipitalis
occipitalis (ok′sip-i-ta′lis)

SYN: occipital. [L.]

occipitalization
occipitalization (ok′sip′i-tal-i-za′shun)

Bony ankylosis between the atlas and occipital bone.

occipito- occipito-

The occiput, occipital structures. [L. occiput]

occipitoatloid
occipitoatloid (ok-sip′i-to-at′loyd)

Relating to the occipital bone and the atlas; denoting the articulation between the two bones.

occipitoaxial
occipitoaxial, occipitoaxoid (ok-sip′i-to-ak′se-al, -ak′soyd)

Relating to the occipital bone and the axis, or epistropheus.

occipitobregmatic
occipitobregmatic (ok-sip′i-to-breg-mat′ik)

Relating to the occiput and the bregma; denoting a measurement in craniometry.

occipitofacial
occipitofacial (ok-sip′i-to-fa′shal)

Relating to the occiput and the face.

occipitofrontal
occipitofrontal (ok-sip′i-to-frun′tal)

1. Relating to the occiput and the forehead. 2. Relating to the occipital and frontal lobe of the cerebral cortex and association pathways that interconnect these regions.

occipitofrontalis
occipitofrontalis (ok-sip′i-to-frun-ta′lis)

See o. (muscle). [L.]

occipitomastoid
occipitomastoid (ok-sip′i-to-mas′toyd)

Relating to the occipital bone and the mastoid process.

occipitomental
occipitomental (ok-sip′i-to-men′tal)

Relating to the occiput and the chin.

occipitoparietal
occipitoparietal (ok-sip′i-to-pa-ri′e-tal)

Relating to the occipital and the parietal bones.

occipitotemporal
occipitotemporal (ok-sip′i-to-tem′po-ral)

Relating to the occiput and the temple, or the occipital and the temporal bones.

occipitothalamic
occipitothalamic (ok-sip′i-to-tha-lam′ik)

Relating to the nerve fibers leading from the occipital lobe of the cerebral cortex to the thalamus.

occiput
occiput, gen. occipitis (ok′si-put, ok-sip′i-tis) [TA]

The back of the head. [L.]

occlude
occlude (o-klood)

1. To close or bring together. 2. To enclose, as in an occluded virus. [see occlusion]

occluder
occluder (o-klood′er)

In dentistry, a name given to some articulators.

occlusal
occlusal (o-kloo′zal)

1. Pertaining to occlusion or closure. 2. In dentistry, pertaining to the contacting surfaces of opposing o. units (teeth or occlusion rims) or the masticating surfaces of the posterior teeth.

occlusion
occlusion (o-kloo′zhun)

1. The act of closing or the state of being closed. 2. In chemistry, the absorption of a gas by a metal or the inclusion of one substance within another (as in a gelatinous precipitate). 3. Any contact between the incising or masticating surfaces of the upper and lower teeth. 4. The relationship between the occlusal surfaces of the maxillary and mandibular teeth when they are in contact. [L. oc- cludo, pp. -clusus, to shut up, fr. ob., against, + claudo, to close]
abnormal o. an arrangement of the teeth that is not considered to be within the normal range of variation.
afunctional o. a malocclusion that does not permit normal function of the dentition.
anterior o. 1. the o. of anterior teeth; 2. SYN: mesial o. (1) .
balanced o. the simultaneous contacting of the upper and lower teeth on the right and left and in the anterior and posterior occlusal areas in centric and eccentric positions within the functional range; used primarily in reference to the mouth, but also arranged and observed on articulators, developed to prevent a tipping or rotating of the denture bases in relation to the supporting structures. SYN: balanced articulation, balanced bite.
bimaxillary protrusive o. an o. in which both the maxilla and mandible protrude, causing the long axes of the maxillary anterior teeth to be at an extremely acute angle to the mandibular teeth; may be secondary to a skeletal or dental deformity, or both; seen commonly in blacks.
buccal o. 1. malposition of a tooth toward the cheek; 2. the o. as seen from the buccal side of the teeth.
centric o. 1. the relation of opposing occlusal surfaces that provides the maximum planned contact and/or intercuspation; 2. the o. of the teeth when the mandible is in centric relation to the maxillae. SYN: centric contact.
coronary o. blockage of a coronary vessel, usually by thrombosis or atheroma, often leading to myocardial infarction.
distal o. 1. a tooth occluding in a position distal to normal; SYN: disto-o., postnormal o., retrusive o. (2) . 2. SYN: distoclusion.
eccentric o. any o. other than centric.
edge-to-edge o. an o. in which the anterior teeth of both jaws meet along their incisal edges when the teeth are in centric o.. SYN: edge-to-edge bite, end-to-end bite, end-to-end o..
end-to-end o. SYN: edge-to-edge o..
functional o. 1. any tooth contacts made within the functional range of the opposing teeth surfaces; 2. o. that occurs during function.
gliding o. SYN: dental articulation.
hyperfunctional o. occlusal stress of tooth or teeth exceeding normal physiologic demands.
labial o. 1. malposition of a tooth in a labial direction; 2. the o. as seen from the labial side of the arches.
lateral o. malposition of a tooth or an entire dental arch in a direction away from the midline.
lingual o. 1. SYN: linguoclusion. 2. interdigitation of the teeth as seen from the internal or lingual aspect.
mechanically balanced o. a balanced o. without reference to physiologic considerations, as on an articulator.
mesenteric artery o. obstruction of arterial flow in the mesenteric circulation by an embolus or thrombus; usually refers to o. of the superior mesenteric artery, although atherosclerotic narrowing may involve all three major splanchnic branches (celiac, superior, and inferior mesenteric).
mesial o. 1. o. in which the mandibular teeth articulate with the maxillary teeth in a position anterior to normal; SYN: anterior o. (2) , mesio-o.. 2. SYN: mesioclusion.
neutral o. 1. an arrangement of teeth such that the maxillary and mandibular first permanent molars are in normal anteroposterior relation; SYN: normal o. (2) . 2. SYN: neutroclusion.
normal o. 1. that arrangement of teeth and their supporting structure that is usually found in health and that approaches an ideal or standard arrangement; SYN: normal bite. 2. SYN: neutral o. (1) .
pathogenic o. an occlusal relationship capable of producing pathologic changes in the supporting tissues.
physiologic o. o. in harmony with functions of the masticatory system.
physiologically balanced o. a balanced o. that is in harmony with the temporomandibular joints and the neuromuscular system.
posterior o. the most effective contact of the molar and bicuspid teeth of both jaws that allows for all the natural movements of the jaws essential to normal mastication and closure. SYN: posteroclusion.
postnormal o. SYN: distal o. (1) .
protrusive o. o. that results when the mandible is protruded forward from centric position.
o. of pupil the presence of an opaque membrane closing the pupillary area.
retrusive o. 1. a biting relationship in which the mandible is forcefully or habitually placed more distally than the patient's centric o.; 2. SYN: distal o. (1) .
spherical form of o. an arrangement of teeth that places their occlusal surfaces on the surface of an imaginary sphere (usually 8 inches in diameter) with its center above the level of the teeth. SEE ALSO: Monson curve.
torsive o. SYN: torsiversion.
traumatic o. SYN: traumatogenic o..
traumatogenic o. a malocclusion capable of producing injury to the teeth and/or associated structures. SYN: traumatic o..
working o. SYN: working contacts, under contact.

occlusive
occlusive (o-kloo′siv)

Serving to close; denoting a bandage or dressing that closes a wound and excludes it from the air.

occlusometer
occlusometer (ok-loo-som′e-ter)

SYN: gnathodynamometer.

occult
occult (o-kult′, ok′ult)

1. Hidden; concealed; not manifest. 2. Denoting a concealed hemorrhage, the blood being inapparent or localized to a site where it is not visible. See o. blood. 3. In oncology, a clinically unidentified primary tumor with recognized metastases. [L. oc-culo, pp. -cultus, to cover, hide]

Oceanospirillum
Oceanospirillum (o′shen-o-spi-ril′um)

A genus of motile, nonsporeforming, aerobic bacteria (family Spirillaceae) containing Gram-negative, rigid, helical cells that are 0.3–1.2 μm in diameter. Motile cells contain bipolar fascicles of flagella. There is no growth anaerobically with nitrate. These organisms are chemoorganotrophic and possess a strictly respiratory metabolism; they neither oxidize nor ferment carbohydrates; found in marine environments. There are at present five species in this genus, of which the type species is O. linum. [L. oceanus, ocean, + spirillum, coil]

ocellus
ocellus, pl .ocelli (o-sel′us, -li)

1. The simple eye found in many invertebrates. SYN: eyespot (2) . 2. Facet of the compound eye of an insect. [L. dim. of oculus, eye]

ochlophobia
ochlophobia (ok-lo-fo′be-a)

Morbid fear of crowds. [G. ochlos, a crowd, + phobos, fear]

Ochoa
Ochoa

Severo, Spanish-U.S. biochemist and Nobel laureate, 1905–1993. See O. law.

ochratoxin
ochratoxin (o-kra-toks′ins)

A mycotoxin produced by Aspergillus ochraceus growing on stored cereal grains. Affects poultry and other animals fed the grain.
o. A o. produced by some species of Aspergillus and Penicillium that can contaminate cereal grains and feeds, primarily following improper storage; a potent carcinogen in rodents.

Ochrobactrum
Ochrobactrum (o-kro-bak′trum)

A Gram-negative genus of bacteria similar to Alcaligenes and Pseudomonas spp. in their distribution in environmental and water sources and their culture characteristics. These have been isolated from a number of clinical sources and appear to be a cause of nosocomial bacteremia.

ochrodermia
ochrodermia (o-kro-der′me-a)

Yellow discoloration of the skin. [G. ochros, pale yellow, + derma, skin]

ochrometer
ochrometer (o-krom′e-ter)

An instrument for determining the capillary blood pressure; one of two adjacent fingers is compressed by a rubber balloon until blanching of the skin occurs, after which the force necessary to accomplish this color change is read in millimeters of mercury. [G. ochros, pale yellow, + metron, measure]

ochronosis
ochronosis (o-kron-o′sis)

A rare, autosomal recessive disease characterized by alkapton uria with pigmentation of the cartilages and sometimes tissues such as muscle, epithelial cells, and dense connective tissue; may affect also the sclera, mucous membrane of the lips, and skin of the ears, face, and hands, and cause standing urine to be dark-colored and contain pigmented casts; pigmentation is thought to result from oxidized homogentisic acid, and cartilage degeneration results in osteoarthritis, particularly of the spine. [G. ochros, pale yellow, + nosos, disease]
exogenous o. pigmentation of the skin of the face and elsewhere from prolonged topical exposure to hydroquinone-containing bleaching creams.

ochronotic
ochronotic (o-kron-ot′ik)

Relating to or characterized by ochronosis.

Ochsner
Ochsner

Albert John, U.S. surgeon, 1858–1925. See O. clamp, O. method.

ocrylate
ocrylate (ok′ri-lat)

A tissue adhesive for surgery.

oct- oct-, octi-, octo-, octa-

Eight. [G. okto, L. octo]

OCTA
OCTA (ok′ta)

An eight–base-pair sequence in DNA that has a regulatory role; for example, if it is artificially appended to a gene, it will cause that gene to be preferentially expressed in cells of the β-lymphocyte lineage.

octacosanoic acid
octacosanoic acid (ok-ta-ko′san-o-ik)

A long-chain fatty acid; found in waxes. SYN: montanic acid.

octad
octad (ok′tad)

1. SYN: octavalent. 2. An octavalent element or radical. [L. octo, eight]

octafluoropropane
octafluoropropane (ok′ta-flor′o-pro-pan)

A drug used for contrast enhancement during ultrasound imaging.

octamethyl pyrophosphoramide
octamethyl pyrophosphoramide (OMPA) (ok-ta-meth′il pi′ro-fos-for′a-mid)

SYN: schradan.

octamylamine
octamylamine (ok-ta-mil′a-men)

An anticholinergic agent.

octan
octan (ok′tan)

Applied to fever, the paroxysms of which recur every eighth day, the day of a paroxysm being counted as the first in the computation. [L. octo, eight]

octandioic acid
octandioic acid

SYN: suberic acid.

octanoate
octanoate (ok′ta-no′at)

SYN: caprylate.

octanoic acid
octanoic acid (ok′ta-no′ik)

SYN: caprylic acid.

octanoyl-CoA synthetase
octanoyl-CoA synthetase (ok′tan-o-il sin′the-tas)

SYN: butyrate-CoA ligase.

octapeptide
octapeptide (ok′ta-pep′tid)

A peptide made up of eight amino acid residues.

octaploidy
octaploidy (ok′ta-ploy′de)

See polyploidy.

octapressin
octapressin (ok′ta-pres′in)

SYN: felypressin.

octavalent
octavalent (ok′ta-va′lent, ok-tav′a-lent)

Denoting a chemical element or radical having a combining power (valency) of eight. SYN: octad (1) .

octavus
octavus (ok-ta′vus)

SYN: vestibulocochlear nerve [CN VIII]. [L.]

octi- octi-

See oct-.

octo- octo-

See oct-.

Octomitidae
Octomitidae (ok-to-mit′i-de)

A family in the protozoan class Zoomastigophorea; flagellates with six to eight flagella arranged in pairs and a body that is bilaterally symmetric; it includes the common human intestinal parasite G. lamblia. [octo- + G. mitos, thread]

Octomitus hominis
Octomitus hominis (ok-tom′i-tus hom′i-nis)

Pentatrichomonas hominis.

octopamine
octopamine (ok-to′pa-men)

A sympathomimetic amine; a false neurotransmitter produced by noradrenergic neurons in the presence of monoamine oxidase inhibitors. SYN: norsympatol, norsynephrine.

octose
octose (ok′tos)

A sugar containing eight carbon atoms.

octoxynol
octoxynol (ok-tok′si-nol)

A surfactant.

octulose
octulose (ok′too-los)

An eight-carbon monoketose.

octulosonic acid
octulosonic acid (ok′too-lo-son′ik)

The -onic acid formally formed by oxidation of carbon atom 1 of octulose to a carboxylic acid group; a condensation product of d-arabinose and phosphoenolpyruvate analogous to neuraminic acid. It forms part of the repeating unit of the polysaccharides of the complex lipopolysaccharides of the Enterobacteriaceae constituting the characteristic somatic octose antigens.

octyl gallate
octyl gallate (ok′til gal′at)

An antioxidant.

octylphenoxy polyethoxyethanol
octylphenoxy polyethoxyethanol (ok′til-fe-nok′se pol′e-eth-ok′se-eth′a-nol)

Mono-p-isooctyl phenyl ether of polyethylene glycol; a surface-active (wetting) agent.

ocular
ocular (ok′u-lar)

1. SYN: ophthalmic. 2. The eyepiece of a microscope, the lens or lenses at the observer end of a microscope, by means of which the image focused by the objective is viewed. [L. oculus, eye]
compensating o. an o. that compensates and corrects for the effects of chromatic aberration in the objective.
Huygens o. the compound o. of a microscope, composed of two planoconvex lenses so arranged that the plane side of each is directed toward the observer.
o. motor relating to or causing movements of the eyeball.
Ramsden o. an eyepiece of a microscope, consisting of two planoconvex lenses with convexities turned to each other.
wide field o. an o. that gives a larger than usual field of view and a high eyepoint.

ocularist
ocularist (ok′u-lar-ist)

One skilled in the design, fabrication, and fitting of artificial eyes and the making of prostheses associated with the appearance or function of the eyes. [L. oculus, eye]

oculentum
oculentum, pl .oculenta (ok-u-len′tum, -ta)

SYN: ophthalmic ointment. [Mod. L., fr. L. oculus, eye]

oculi
oculi (ok′u-li)

Plural of oculus. [L.]

oculist
oculist (ok′u-list)

SYN: ophthalmologist. [L. oculus, eye]

oculo- oculo-

The eye, ocular. SEE ALSO: ophthalmo-. [L. oculus]

oculoauriculovertebral
oculoauriculovertebral (ok′u-lo-aw-rik′u-lo-ver′te-bral)

Relating to the eyes, ears, and vertebrae.

oculocardiac
oculocardiac (ok′u-lo-kar′de-ak)

Relating to the eyes and heart.

oculocerebrorenal
oculocerebrorenal (ok′u-lo-ser′e-bro-re′nal)

Relating to the eyes, brain, and kidneys.

oculocutaneous
oculocutaneous (ok′u-lo-ku-ta′ne-us)

Relating to the eyes and the skin.

oculodentodigital
oculodentodigital (ok′u-lo-den′to-dij′i-tal)

Relating to the eyes, teeth, and fingers.

oculodermal
oculodermal (ok′u-lo-der′mal)

Relating to the eyes and skin.

oculodynia
oculodynia

Pain in the eyeball. SYN: ophthalmalgia. [ophthalmo- + G. algos, pain]

oculofacial
oculofacial (ok-u-lo-fa′shal)

Relating to the eyes and the face.

oculography
oculography (ok-u-log′ra-fe)

A method of recording eye position and movements. [oculo- + G. graphe, a writing]
photosensor o. o. in which photocells are directed to the surface of the eye to record rotations.

oculogyria
oculogyria (ok′u-lo-ji′re-a)

The limits of rotation of the eyeballs. [oculo- + G. gyros, circle]

oculogyric
oculogyric (ok′u-lo-ji′rik)

Referring to rotation of the eyeballs; characterized by oculogyria.

oculomandibulodyscephaly
oculomandibulodyscephaly (ok′u-lo-man-dib′u-lo-dis-sef′a-le)

SYN: dyscephalia mandibulo-oculofacialis.

oculomotor
oculomotor (ok′u-lo-mo′tor)

Pertaining to the o. cranial nerve. [L. oculomotorius, fr. oculo- + L. motorius, moving]

oculomotorius
oculomotorius (ok′u-lo-mo-to′re-us)

SYN: oculomotor nerve [CN III]. [L.]

oculonasal
oculonasal (ok′u-lo-na′sal)

Relating to the eyes and the nose. [oculo- + L. nasus, nose]

oculopathy
oculopathy (ok-u-lop′a-the)

SYN: ophthalmopathy.

oculoplethysmography
oculoplethysmography (ok′u-lo-pleth-iz-mog′ra-fe)

Indirect measurement of the hemodynamic significance of internal carotid artery stenosis or occlusion by demonstration of an ipsilateral delay in the arrival of ocular pressure transmitted from branches of the ophthalmic artery. [oculo- + G. plethymos, increase, + graphe, to write]

oculopneumoplethysmography
oculopneumoplethysmography (ok′u-lo-noo′mo-pleth-iz-mog′ra-fe)

A method of bilateral measurement of ophthalmic artery pressure that reflects pressure and flow in the internal carotid artery. See oculoplethysmography.

oculopupillary
oculopupillary (ok′u-lo-poo′pi-lar-e)

Pertaining to the pupil of the eye.

oculosympathetic
oculosympathetic (ok′oo-lo-sim-pa-the′tik)

Pertaining to the sympathetic pathway to the eye, damage to which produces Horner syndrome.

oculovertebral
oculovertebral (ok′u-lo-ver′te-bral)

Relating to the eyes and vertebrae.

oculozygomatic
oculozygomatic (ok′u-lo-zi-go-mat′ik)

Relating to the orbit or its margin and the zygomatic bone.

oculus
oculus, gen. and pl. oculi (ok′u-lus, -li) [TA]

SYN: eye (1) . [L.]

ocy- ocy-

See oxy-.

ocytocin
ocytocin (o-si-to′sin)

SYN: oxytocin. [G. okytokos, fast birth, prompt delivery]

OD
OD

Abbreviation for overdose; optic density (see absorbance).

O.D.
O.D.

1. Abbreviation for L. oculus dexter, right eye. 2. Abbreviation for Doctor of Optometry. See optometrist.

o.d.
o.d.

Abbreviation for L. omni die, every day.

odaxesmus
odaxesmus (o′dak-sez′mus)

A biting sensation; a form of paresthesia. [G. odaxesmos, an irritation, fr. odax (adv.), by biting.]

odaxetic
odaxetic (o′dak-set′ik)

1. Causing formication or itching. 2. A substance or agent that causes formication or itching. [G. odaxesmos, an irritation]

Oddi
Oddi

Ruggero, Italian physician; 1864–1913. See O. sphincter.

odds
odds

The ratio of probability of occurrence to non-occurrence of an event. [pl. of odd, fr. M.E. odde, fr. O.Norse oddi, odd number]

-odes -odes

Having the form of, resembling. [G. eidos, form, resemblance]

Odland body
Odland body

See under body.

odogenesis
odogenesis (o-do-jen′e-sis)

SYN: neurocladism. [G. hodos, path, + genesis, source]

odont- odont-, odonto-

A tooth, teeth. [G. odous (odont-)]

odontagra
odontagra (o-don-tag′ra)

Obsolescent term for toothache thought to be of gouty origin. [odonto- + G. agra, seizure]

odontalgia
odontalgia (o-don-tal′je-a)

SYN: toothache. [odont- + G. algos, pain]
o. dentalis reflex pain in the ear due to dental disease, usually propagated along the auriculotemporal nerve.

odontalgic
odontalgic (o-don-tal′jik)

Relating to or marked by toothache.

odontectomy
odontectomy (o-don-tek′to-me)

Removal of teeth by the reflection of a mucoperiosteal flap and excision of bone from around the root or roots before the application of force to effect the tooth removal. [odont- + G. ektome, excision]

odonterism
odonterism (o-don′ter-izm)

Chattering of the teeth. [odont- + G. erismos, quarrel]

odontiasis
odontiasis (o-don-ti′a-sis)

SYN: teething.

odontinoid
odontinoid (o-don′ti-noyd)

1. Resembling dentin. 2. A small excrescence from a tooth, most common on the root or neck. 3. Toothlike.

odontitis
odontitis (o-don-ti′tis)

SYN: pulpitis.

odonto- odonto-

See odont-.

odontoameloblastoma
odontoameloblastoma (o-don′to-am′e-lo-blas-to′ma)

SYN: ameloblastic odontoma.

odontoblast
odontoblast (o-don′to-blast)

One of the dentin-forming cells, derived from mesenchyme of neural crest origin, lining the pulp cavity of a tooth; odontoblasts are arranged in a peripheral layer in the dental pulp, each with an odontoblastic process extending through the thickness of the dentine; the cells generally are columnar in the coronal pulp but are more cuboidal in the radicular area and adjacent to tertiary dentin. [odonto- + G. blastos, sprout, germ]

odontoblastoma
odontoblastoma (o-don′to-blas-to′ma)

1. A tumor composed of neoplastic epithelial and mesenchymal cells that may differentiate into cells able to produce calcified tooth substances. 2. An odontoma in its early formative stage. [odontoblast + G. -oma, tumor]

odontoclast
odontoclast (o-don′to-klast)

One of the cells believed to produce resorption of the roots of the deciduous teeth. [odonto- + G. klastos, broken]

odontodynia
odontodynia (o-don-to-din′e-a)

SYN: toothache. [odonto- + G. odyne, pain]

odontodysplasia
odontodysplasia (o-don′to-dis-pla′ze-a)

A developmental disturbance of one or of several adjacent teeth, of unknown etiology, characterized by deficient formation of enamel and dentin, which results in an abnormally large pulp chamber and imparts a ghostlike radiographic image to the teeth; such teeth exhibit delayed eruption into the oral cavity. SYN: odontogenesis imperfecta, odontogenic dysplasia.

odontogenesis
odontogenesis (o-don-to-jen′e-sis)

The process of development of the teeth. SYN: odontogeny, odontosis. [odonto- + G. genesis, production]
o. imperfecta SYN: odontodysplasia.

odontogeny
odontogeny (o-don-toj′e-ne)

SYN: odontogenesis.

odontoid
odontoid (o-don′toyd)

1. Shaped like a tooth. SYN: dentoid. 2. Relating to the toothlike o. process of the second cervical vertebra. [odont- + G. eidos, resemblance]

odontology
odontology (o-don-tol′o-je)

SYN: dentistry. [odonto- + G. logos, study]
forensic o. SYN: forensic dentistry.

odontoloxia
odontoloxia, odontoloxy (o-don-to-lok′se-a, o-don-tol′ok-se)

SYN: odontoparallaxis. [odonto- + G. loxos, slanting]

odontolysis
odontolysis (o-don-tol′i-sis)

SYN: erosion (3) . [odonto- + G. lysis, dissolution]

odontoma
odontoma (o-don-to′ma)

1. A tumor of odontogenic origin. 2. A hamartomatous odontogenic tumor composed of enamel, dentin, cementum, and pulp tissue that may or may not be arranged in the form of a tooth. [odonto- + G. -oma, tumor]
ameloblastic o. a benign mixed odontogenic tumor composed of an undifferentiated component histologically identical to an ameloblastoma and a well-differentiated component identical to an o.; appears as a mixed radiolucent-radiopaque lesion and presents clinically as an ameloblastoma. SYN: odontoameloblastoma.
complex o. an o. in which the various odontogenic tissues are organized in a haphazard arrangement with no resemblance to teeth.
compound o. an o. in which the odontogenic tissues are organized and resemble anomalous teeth.

odontoneuralgia
odontoneuralgia (o-don′to-noo-ral′je-a)

Facial neuralgia caused by a carious tooth.

odontonomy
odontonomy (o-don-ton′o-me)

Dental nomenclature. [odonto- + G. onoma, name]

odontonosology
odontonosology (o-don′to-no-sol′o-je)

SYN: dentistry. [odonto- + G. nosos, disease, + logos, study]

odontoparallaxis
odontoparallaxis (o-don′to-par-a-lak′sis)

Irregularity of the teeth. SYN: odontoloxia, odontoloxy. [odonto- + G. parallax, alternately]

odontopathy
odontopathy (o-don-top′a-the)

Any disease of the teeth or of their sockets. [odonto- + G. pathos, suffering]

odontophobia
odontophobia (o-don-to-fo′be-a)

Morbid fear of teeth. [odonto- + G. phobos, fear]

odontoplasty
odontoplasty (o-don′to-plas-te)

Surgical contouring of tooth surface to enhance plaque control and gingival morphology. [odonto- + G. plasso, to mold]

odontoprisis
odontoprisis (o-don-top′ri-sis)

Grinding together of the teeth. SEE ALSO: bruxism. [odonto- + G. prisis, a sawing, a grinding]

odontoptosis
odontoptosis (o-don-top-to′sis, -to-to′sis)

Downward movement of an upper tooth due to the loss of its lower antagonist(s). SEE ALSO: supereruption. [odonto- + G. ptosis, a falling]

odontorrhagia
odontorrhagia (o-don-to-ra′je-a)

Profuse bleeding from the socket after the extraction of a tooth. [odonto- + G. rhegnymi, to burst forth]

odontoschism
odontoschism (o-don′to-skizm, -sizm)

Fissure of a tooth. [odonto- + G. schisma, a cleft]

odontoscope
odontoscope (o-don′to-skop)

An optical device, similar to a closed circuit television system, that projects a view of the oral cavity onto a screen for multiple viewing.

odontoscopy
odontoscopy (o-don-tos′ko-pe)

1. Examination of the oral cavity by means of the odontoscope. 2. Examination of the markings in prints of the cutting edges of the teeth; used, like fingerprints, as a method of personal identification. [odonto- + G. skopeo, to view]

odontosis
odontosis (o-don-to′sis)

SYN: odontogenesis.

odontotherapy
odontotherapy (o-don-to-thar′a-pe)

Treatment of diseases of the teeth.

odontotomy
odontotomy (o-don-tot′o-me)

Cutting into the crown of a tooth. [odonto- + G. tome, incision]
prophylactic o. a preventive operation in which imperfectly formed developmental grooves, pits, and fissures are opened up by means of a bur and filled to obviate future decay.

odor
odor (o′dor)

Emanation from any substance that stimulates the olfactory sensory cells. SYN: scent, smell (3) . [L.]

odorant
odorant (o′dor-ant)

A substance with an odor.

odoratism
odoratism (o-dor′a-tizm)

See lathyrism. [fr. Lathyrus odoratus, sweet pea]

odoriferous
odoriferous (o-do-rif′er-us)

Having a scent, perfume, or odor. SYN: odorous. [odor + L. fero, to bear]

odorimeter
odorimeter (o′do-rim′e-ter)

Instrument for performing odorimetry.

odorimetry
odorimetry (o′do-rim′e-tre)

The determination of the comparative power of different substances in stimulating olfactory sensations. [odor + G. metron, measure]

odorivection
odorivection (o′dor-i-vek′shun)

Conveying or bearing an odor, as in the air. [odor + L. vector, a carrier]

odorography
odorography (o′do-rog′ra-fe)

Description of odors. [odor + G. graphe, a description]

odorous
odorous (o′dor-us)

SYN: odoriferous.

O'Dwyer
O'Dwyer

Joseph P., U.S. physician, 1841–1898. See O. tube.

odyn- odyn-, odyno-

Pain. [G. odyne]

odynacusis
odynacusis (o-din′a-koo′sis)

Hypersensitiveness of the organ of hearing, so that sounds cause actual pain. [odyn- + G. akouo, to hear]

odynophagia
odynophagia (o-din-o-fa′je-a)

Pain on swallowing. [odyno- + G. phago to eat]

odynophonia
odynophonia (o-din-o-fo′ne-a)

Pain on using the voice. [odyno- + G. phone, sound, voice]

Oe
Oe

Symbol for oersted.

oe- oe-

For words so beginning and not found here, see e-.

oedipism
oedipism (ed′i-pizm)

1. Manifestation of the Oedipus complex. 2. Rarely used term for self-infliction of injury to the eyes, usually an attempt at evulsion. [Oedipus, G. myth. char.]

Oehl
Oehl

Eusebio, Italian anatomist, 1827–1903. See O. muscles, under muscle.

oenanthal
oenanthal (e-nan′thal)

SYN: heptanal.

oersted
oersted (Oe) (er′sted)

A unit of magnetic field intensity; the magnetic field intensity that exerts a force of 1 dyne on a unit magnetic pole; equal to (1000/4π) A m⁻¹. [Hans-Christian O., Danish physicist, 1777–1851]

oesophagostomiasis
oesophagostomiasis ( e-sof′a-go-sto-mi′a-sis)

Infection with nematode parasites of the genus Oesophagostomum. SYN: esophagostomiasis. [G. oi-sophagos, gullet (esophagus), + stoma, mouth, + -iasis, condition]

Oesophagostomum
Oesophagostomum (e-sof-a-gos′to-mum)

A genus of strongyle nematodes (subfamily Oesophagostominae) that encyst in the intestinal wall of herbivores and primates, causing nodular disease. Larvae appear to stimulate a host reaction in the intestinal wall, forming nodules in which the worms complete their development (unless the host is immune); they then leave the nodule and feed as adults in the lumen of the large intestine. [G. oisophagos, gullet (esophagus), + stoma, mouth]
O. apiostomum a nematode species that has been reported in northern Nigeria and central Africa to encyst under the submucosa of the human intestine and occasionally cause dysentery; a common parasite of monkeys and apes, both in captivity and in the wild.
O. brevicaudum a nematode species that occurs in the cecum and colon of pigs in North America and India.
O. brumpti a nematode species described from African monkeys and reported occasionally in humans.
O. columbianum a nematode species that occurs in sheep, goats, and wild African antelopes; except when present in large numbers, it does not appear to seriously affect the health of the host.
O. dentatum a nematode species that affects the colon of swine; the lesions are similar to those in sheep.
O. georgianum a nematode species that occurs in the cecum and colon of pigs in the U.S.
O. quadrispinulatum a species that occurs in the cecum and colon of pigs in the Americas, Europe, and Southeast Asia.
O. radiatum a species that occurs worldwide in cattle and water buffalo; the lesions are similar to those of sheep.
O. stephanostomum a species of nematode occurring in chimpanzees, monkeys, and gorillas in Africa, but also reported from humans and monkeys in Brazil.
O. venulosum a species that occurs worldwide in the cecum and colon of cattle, sheep, goats, deer, and many other ruminants.

oestradiol
oestradiol (es-tra-di′ol)

SYN: estradiol.

oestrids
oestrids (est′ridz)

Common name for botflies of the family Oestridae, such as Oestrus. [G. oistros, gadfly]

oestriol
oestriol (es′tre-ol)

SYN: estriol.

oestrogen
oestrogen (es′tro-jen)

SYN: estrogen.

oestrone
oestrone (es′tron)

SYN: estrone.

oestrosis
oestrosis (es-tro′sis)

Infection of small ruminants and, rarely, humans with larvae of the fly Oestrus ovis.

Oestrus
Oestrus (es′tus)

A genus of tissue-invading flies that cause myiasis in sheep; the head botflies in the family Oestridae. O. ovis (a nose fly) is a grayish brown, robust, hairy, beelike botfly, imported from Europe, and now a serious pest in parts of the U.S.; larvae are deposited by the adult fly in the nostrils of sheep, and inch-long larvae develop in the paranasal sinuses, causing considerable mucous discharge and distress in old or weak sheep. [G. oistros, gadfly]

official
official (o-fish′al)

Authoritative; denoting a drug or a chemical or pharmaceutical preparation recognized as standard in the pharmacopeia. Cf.:officinal. [L. officialis, fr. officium, a favor, service, fr. opus, work, + facio, to do]

officinal
officinal (o-fis′i-nal)

Denoting a chemical or pharmaceutical preparation kept in stock, in contrast to magistral (prepared extemporaneously according to a physician's prescription); an o. preparation is often, though not necessarily, official. [L. officina, shop]

Ogino
Ogino

Kyusaka, 20th century Japanese physician. See O.-Knaus rule.

Ogston
Ogston

Sir Alexander, Scottish surgeon, 1844–1929. See O. line, O.-Luc operation.

Oguchi
Oguchi

Chita, Japanese ophthalmologist, 1875–1945. See O. disease.

Ogura
Ogura

Joseph H., U.S. otolaryngologist, 1915–1983. See O. operation.

O'Hara
O'Hara

Michael, Jr., U.S. surgeon, 1869–1926. See O. forceps.

OHI
OHI

Abbreviation for Oral Hygiene Index.

OHI-S
OHI-S

Abbreviation for Simplified Oral Hygiene Index.

Ohm
Ohm

Georg S., German physicist, 1787–1854. See o., O. law.

ohm
ohm (Ω) (om)

The practical unit of electrical resistance; the resistance of any conductor allowing 1 A of current to pass under the electromotive force of 1 V. [G.S. O.]

ohmammeter
ohmammeter (om-am′e-ter)

A combined ohmmeter and ammeter.

ohmmeter
ohmmeter (om′e-ter)

An instrument for determining the resistance, in ohms, of a conductor.

ohne Hauch
ohne Hauch (o′na howch)

Term used to designate the nonspreading growth of nonflagellated bacteria on agar media; also applied to somatic agglutination. SEE ALSO: O antigen. [Ger. without breath]

Ohngren line
Ohngren line

See under line.

OI
OI

Abbreviation for osteogenesis imperfecta.

oi- oi-

For words so beginning and not found here, see e-.

-oid -oid

Resemblance to, equivalent to Eng. -form. [G. eidos, form, resemblance]

oidia
oidia (o-id′ea)

Plural of oidium.

oidium
oidium, pl .oidia (o-id′e-um, o-id′e-a)

Formerly used term for arthroconidium. [Mod. L. dim. of G. oon, egg]

oil
oil (oyl)

An inflammable liquid, of fatty consistency and unctuous feel, which is insoluble in water, soluble or insoluble in alcohol, and freely soluble in ether. Oils are variously classified as animal, vegetable, and mineral oils according to their source (the mineral oils probably being of remote animal and vegetable origin); into fatty (fixed) and volatile oils; and into drying and nondrying (fatty) oils, the former becoming gradually thicker when exposed to the air and finally drying to a varnish, the latter not drying but liable to become rancid on exposure. Many of the oils, both fixed and volatile, are used in medicine. For individual oils, see the specific names. [L. oleum; G. elaion, originally olive o.]
absolute oils essential oils that are obtained by the removal of insoluble compounds from concrete oils.
o. of American wormseed SYN: o. of chenopodium.
o. of anise volatile o. derived from the dried ripe fruit of Pimpinella anisum (family Umbelliferae) or of Illicium verum, (family Magnoliaceae) (Chinese star anise); has a characteristic anise aroma, resembling fennel. Used in manufacture of liqueurs, and as flavoring for candies, cookies, dentifrices. Pharmaceutical aid (flavor). Carminative.
o. of bay volatile o. derived by steam distillation of the dried leaves of Pimenta (Myrcia) acris (family Myrtaceae); o. of myrcia; used as an aromatic in the manufacture of bay rum and as a pharmaceutical aid.
o. of bergamot volatile o. derived by steam distillation from the rind of the fresh fruit of Citrus aurantium or C. bergamia; contains l-linalyl acetate, l-linalool; d-limonene, dipentene, bergaptene; used as a deodorant in preparations containing malodorous ingredients and as an aromatic in perfumes, hairdressings, and pomades.
betula o. o. of sweet birch, a volatile o. obtained by distillation from the bark of Betula lenta (sweet birch); used as a flavoring agent and as a counterirritant liniment. SEE ALSO: methyl salicylate.
o. of bitter almond volatile o. from the dried ripe kernels of bitter almonds or from other kernels containing amygdalin, such as apricots, peaches, plums, and cherries; obtained by steam distillation subsequent to maceration of the source with water. Formerly used as an antipruritic; poisonous—releases hydrocyanic acid (hydrogen cyanide). Only the o. free of hydrogen cyanide may be used to flavor liquors and foods.
o. of bitter orange volatile o. obtained by steam distillation from the fresh peel of Citrus aurantium (family Rutaceae). Aromatic material used as a flavoring agent in pharmaceuticals and foods and liquors; also used in perfumes.
o. of cardamom volatile o. obtained by steam distillation from the seeds of Elettaria cardamomum (family Zingiberacea.) A flavoring agent in pharmaceuticals (syrups), liquors, sauces, confections, and baked goods; formerly used as a carminative.
o. of chenopodium volatile o. from the fresh above-ground part of the flower American wormseed, Chenopodium ambrosioides, or C. anthelminticum. Used as an anthelmintic. SYN: o. of American wormseed.
o. of cherry laurel volatile o. derived by steam distillation from Prunus laurocerasus (family Rosaceae); similar to o. of bitter almond; highly toxic because of hydrogen cyanide content.
o. of cinnamon volatile o. obtained by steam distillation from the leaves and twigs of Cinnamomum cassia (family Lauracea). A flavor in foods and perfumes.
o. of citronella volatile o. obtained by steam distillation of fresh lemon grass. Contains citranellol; used as an insect repellent either on the skin or in the form of incense; also used as a perfume.
o. of clove volatile o. obtained by steam distillation of the dried flower buds of Eugenia caryophyllata (family Myrtacea). Contains about 85% eugenol along with other constituents. Used in dentistry as a local anesthetic and component of temporary fillings of the teeth. Also used to flavor foods; strong, pungent odor. SYN: clove o..
concrete oils essential oils obtained by extraction with organic solvents; contain waxes and paraffins.
o. of coriander volatile o. from the dried ripe fruit of Coriandrum sativum (family Umbelliferae). Flavoring in foods and alcoholic beverages.
o. of crispmint SYN: o. of spearmint.
o. of cubeb volatile o. of the unripe fruit of Piper cubeba (family Piperaceae). Formerly used as a urinary antiseptic.
o. of curled mint SYN: o. of spearmint.
o. of dwarf pine needles volatile o. from the fresh leaves of Pinus montana (family Pinaceae). Pleasant pine odor; used as a pharmaceutical aid (flavor and perfume). Has been used as an expectorant.
essential oils plant products, usually somewhat volatile, giving the odors and tastes characteristic of the particular plant, thus possessing the essence, e.g., citral, pinene, camphor, menthane, terpenes; usually, the steam distillates of plants or oils of plants obtained by pressing out the rinds of a particular plant. SEE ALSO: volatile o..
ethereal o. SYN: volatile o..
o. of eucalyptus volatile o. from the fresh leaves of Eucalyptus globulus (family Myrtaceae) and some other species of Eucalyptus; native to Australia; pungent o. with a spicy, cooling taste. Has been used as an aromatic in inhalants, as an expectorant, anthelmintic, and local antiseptic.
fatty o. an o. derived from both animals and plants; chemically, a glyceride of a fatty acid that, by substitution of the glycerine by an alkaline base, is converted into a soap; a fatty o., in contrast to a volatile o., is permanent, leaving a stain on an absorbent surface, and thus is not capable of distillation; it is obtained by expression or extraction; the consistency varies with the temperature, some being liquid (o.'s proper), others semisolid (fats), and others solid (tallows) at ordinary temperatures; both liquid and semisolid oils are congealed by cold and the solids are liquified by heat. SYN: fixed o..
o. of fennel volatile o. from the dried fruit of Foeniculum vulgare (family Umbelliferae). An aromatic o. with the odor and taste of fennel, similar to anise; used as a flavoring agent in pharmaceuticals. Has been used as a carminative.
fixed o. SYN: fatty o..
fusel o. a mixture of side products of alcoholic fermentation; consists primarily of alcohols ( e.g., amyl, propyl, isoamyl, and isobutyl alcohols).
joint o. SYN: synovial fluid.
jojoba o. a liquid wax ester mixture extracted from ground or crushed seeds from Simmondsia chinensis and S. californica (family Buxaceae), desert shrubs native to Arizona, California, and northern Mexico. Used extensively in cosmetics for alleged skin softening and lubricating properties; other uses include as lubricant, fuel, chemical feedstock, substitute for sperm whale o.. SYN: o. of jojoba.
o. of jojoba SYN: jojoba o..
o. of juniper volatile o. from the dried ripe fruit (berries) of Juniperus communis (family Cupressaceae). Formerly used as a diuretic. Used in perfumery. SYN: juniper berry o..
o. of lavender volatile o. from fresh flowering tops of Lavandula officinalis (family Labiatae). Aromatic o. used in perfume and as a flavoring agent. Has been used as a carminative.
o. of lemon volatile o. expressed from fresh peel of Citrus limonum (family Rutaceae). Aromatic o. used for flavoring pharmaceuticals, liqueurs, pastry, foods, and beverages and in perfumes.
o. of lemon grass volatile o. from Cymbopogon citratus and of C. flexuosus (family Gramineae). Used in perfumery and as a source of citral for the synthesis of vitamin A.
Lorenzo o. a mixture of four parts glyceryl trioleate and one part glyceryl trierucate; used in treatment of adrenoleukodystrophy. [for Lorenzo Odone, a child with adrenoleukodystrophy, whose family's discovery and support of this agent were dramatized in the U.S. film Lorenzo's O. (1992)]
olive o. The expressed o. of the fruit of Olea europaea; used as a cholagogue, laxative, and emollient, in the preparation of liniments, and in the preparation of foods.
palm o. an o. obtained from the seeds of Elaeis guineensis (family Palmae); used in the manufacture of soap, liniments, and ointments and also in foods.
o. of pennyroyal either American or European. The former is a volatile o. derived from the flowering tops and leaves of Hedeoma pulegioides (family Labiatae). Contains pulegone and ketones. European is o. of pulegium; a volatile o. from Mentha pulegium (family Labiatae); about 85% pulegone. Has been used as an aromatic carminative, abortifacient, and insect repellent.
o. of peppermint a volatile o. containing menthol (not less than 50% of total) obtained by steam distillation from the fresh flowering plant Mentha piperita (family Labiatae). Used as a pharmaceutical aid (flavor) and in flavoring liqueurs; a carminative.
red o. [C.I. 26125] a weakly acid diazo o.-soluble dye, used in histologic demonstration of neutral fats.
rock o. (rok oyl) SYN: petroleum.
o. of rose a volatile o. from the fresh flowers of Rosa gallica and R. damascena and other members of the Rosaceae family. Used largely in perfumery, ointments, and toilet preparations. SYN: attar of rose, essence of rose, otto of rose.
o. of spearmint volatile o. from the flowering tops of Mentha spicata (family Labiatae, pharmaceutical aid (flavor) and a carminative. SYN: o. of crispmint, o. of curled mint.
sweet birch o. SYN: methyl salicylate.
o. of turpentine volatile o. distilled from the oleoresin and obtained from Pinus palastrus (family Pinaceae) and other species of Pinus yielding terpene oils. Solvent for oils, resins, varnishes; also used as vehicle, thinner, and remover of o.-based paints; rubefacient; has been used as a counterirritant in liniments.
volatile o. a substance of oily consistency and feel, derived from a plant and containing the principles to which the odor and taste of the plant are due (essential o.); in contrast to a fatty o., a volatile o. evaporates when exposed to the air and thus is capable of distillation; it may also be obtained by expression or extraction; many volatile oils, identical to or closely resembling the natural oils, can be made synthetically. Volatile oils are used in medicine as stimulants, stomachics, correctives, and carminatives, and for purposes of flavoring ( e.g., peppermint o.). SYN: ethereal o..
o. of wormwood volatile o. from leaves and tops of Artemisia absinthium (family Compositae). Thujol alcohol and acetate; thujone (a powerful convulsant), phellandrene, cadinene; also a blue o.. Used in flavoring of vermouth and, formerly, in absinthe.

oil of vitriol
oil of vitriol

SYN: sulfuric acid.

ointment
ointment (oynt′ment)

A semisolid preparation usually containing medicinal substances and intended for external application. O. bases used as vehicles fall into four general classes: 1) Hydrocarbon bases (oleaginous o. bases) keep medicaments in prolonged contact with the skin, act as occlusive dressings, and are used chiefly for emollient effects. 2) Absorption bases either permit the incorporation of aqueous solutions with the formation of a water-in-oil emulsion or are water-in-oil emulsions that permit the incorporation of additional quantities of aqueous solutions; such bases permit better absorption of some medicaments and are useful as emollients. 3) Water-removable bases (creams) are oil-in-water emulsions containing petrolatum, anhydrous lanolin, or waxes; they may be washed from the skin with water and are thus more acceptable for cosmetic reasons; they favor absorption of serous discharges in dermatologic conditions. 4) Water-soluble bases (greaseless o. bases) contain only water-soluble substances. SEE ALSO: cerate. SYN: salve, uncture, unguent. [O. Fr. oignement; L. unguo, pp. unctus, to smear]
blue o. a grease-based o. containing 20% finely divided metallic mercury, formerly widely used for local application to the skin for the destruction of body lice. Risk is associated with transdermal absorption of mercury and a local dermatitis. SYN: mild mercurial o..
eye o. SYN: ophthalmic o..
hydrophilic o. an o. base consisting of 25% each of white petrolatum and stearyl alcohol, 12% propyl glycol emulsified in 37% water by 1% of lauryl sulfate; preserved with paraben. Suitable for the incorporation of numerous drugs intended for local application; a washable o. base.
mild mercurial o. SYN: blue o..
ophthalmic o. a special o. for application to the eye that must be free from particles and must be nonirritating to the eye. SYN: eye o., oculentum.

Okazaki
Okazaki

Reiji (1930–1975) and Tuneko, 20th century Japanese molecular biologists. See O. fragment.

-ol -ol

Suffix denoting that a substance is an alcohol or a phenol.

olamine
olamine (ol′a-men)

USAN-approved contraction for ethanolamine.

Oldfield
Oldfield

Michael C., 20th century English physician. See O. syndrome.

oleaginous
oleaginous (o-le-aj′i-nus)

Oily or greasy. [L. oleagineus, pertaining to olea, the olive tree]

oleander
oleander (o-le-an′der)

The bark and leaves of Nerium o. (family Apocynaceae), a shrub of the eastern Mediterranean; formerly used as a diuretic and heart tonic.

oleandomycin phosphate
oleandomycin phosphate (o-le-an-do-mi′sin)

An antibiotic substance produced by species of Streptomyces antibioticus; effective against staphylococci, streptococci, pneumococci, and some Gram-negative bacteria.

oleate
oleate (o′le-at)

1. A salt of oleic acid. 2. A pharmacopeial preparation consisting of a combination or solution of an alkaloid or metallic base in oleic acid, used as an inunction.

olecranon
olecranon (o-lek′ra-non, o′le-kra′non) [TA]

The prominent curved proximal extremity of the ulna, the upper and posterior surface of which gives attachment to the tendon of the triceps muscle, the anterior surface entering into the formation of the trochlear notch. SYN: elbow bone, o. process, point of elbow, tip of elbow. [G. the head or point of the elbow, fr. olene, ulna, + kranion, skull, head]

olefin
olefin (o′le-fin)

SYN: alkene.

oleic acid
oleic acid (o-le′ik)

An unsaturated fatty acid that is the most widely distributed and abundant fatty acid in nature; used commercially in the preparation of oleates and lotions, and as a pharmaceutical solvent. Cf.:elaidic acid. [L. oleum, oil]

olein
olein (o′le-in)

Trioleoyl glycerol; glyceryl trioleate;a triacylglycerol, solely containing oleoyl moieties, found in fats and oils. SYN: triolein.

oleo- oleo-

Oil. SEE ALSO: eleo-. [L. oleum]

oleogomenol
oleogomenol (o′le-o-go′men-ol)

SYN: gomenol.

oleogranuloma
oleogranuloma (o′le-o-gran-u-lo′ma)

SYN: lipogranuloma.

oleoma
oleoma (o-le-o′ma)

SYN: lipogranuloma.

oleometer
oleometer (o-le-om′e-ter)

An instrument, similar to a hydrometer, for determining the specific gravity of oils. SYN: eleometer. [oleo- + G. metron, measure]

oleopalmitate
oleopalmitate (o′le-o-pal′mi-tat)

A double salt of oleic and palmitic acids.

oleoresin
oleoresin (o′le-o-rez′in)

1. A compound of an essential oil and resin, present in certain plants. 2. A pharmaceutical preparation. See aspidium, capsicum, ginger. 3. SYN: balsam.

oleosaccharum
oleosaccharum, pl .oleosacchara (o′le-o-sak′a-rum)

A class of preparations made by the trituration of a volatile oil (such as anise, fennel, or lemon) with sugar; used as a diluent or corrigent of powerful or bad-tasting drugs in powder form. SYN: oil sugar. [oleo- + G. saccharon, sugar]

oleostearate
oleostearate (o′le-o-ste′a-rat)

A double salt of oleic and stearic acids.

oleosus
oleosus (o-le-o′sus)

Greasy; relating to abnormality of the sebaceous apparatus. [L., fr. oleum, oil]

oleotherapy
oleotherapy (o′le-o-thar′a-pe)

Treatment of disease by an oil given internally or applied externally. SYN: eleotherapy. [oleo- + G. therapeia, therapy]

oleovitamin
oleovitamin (o′le-o-vi′ta-min)

A solution of a vitamin in an edible oil.
o. A and D a solution of vitamins A and D in fish liver oil or in an edible vegetable oil.

oleum terebinthinae
oleum terebinthinae (o′le-um ter-e-ben′thin-i)

SYN: turpentine oil.

oleyl alcohol
oleyl alcohol (o-le′il)

A mixture of aliphatic alcohols consisting chiefly of CH₃(CH₂)₇CH&dbond;CH(CH₂)₇CH₂OH; used as an emulsifying aid and in the preparation of cold cream; found in fish oils.

oleyl-CoA
oleyl-CoA (o-le′il)

A product of the Δ⁹-desaturase enzyme system in the biosynthesis of monounsaturated fatty acids. SYN: oleyl-coenzyme A.

oleyl-coenzyme A
oleyl-coenzyme A

SYN: oleyl-CoA.

olfactie
olfactie, olfacty (ol-fak′te)

The unit of smell; the threshold of olfactory stimulation, or the point at which the smell is just received in the olfactometer. [see olfaction]

olfaction
olfaction (ol-fak′shun)

1. The sense of smell. SYN: smell (2) . 2. The act of smelling. SYN: osmesis, osphresis. [L. ol- facio, pp. -factus, to smell]

olfactology
olfactology (ol′fak-tol′-o-je)

Study of the sense of smell. [olfaction + G. logos, study]

olfactometer
olfactometer (ol′fak-tom′e-ter)

A device for estimating the sensitivity to odorants. [L. olfactus, smell, + G. metron, measure]

olfactometry
olfactometry (ol′fak-tom′e-tre)

Determination of the degree of sensitivity to odorants.

olfactophobia
olfactophobia (ol-fak-to-fo′be-a)

Morbid fear of odors. SYN: osmophobia, osphresiophobia. [L. olfactus, smell, + G. phobos, fear]

olfactory
olfactory (ol-fak′to-re)

Relating to the sense of smell. SYN: osmatic, osphretic. [see olfaction]

olibanum
olibanum (o-lib′a-num)

A gum resin from several trees of the genus Boswellia (family Burseraceae); has been used as a stimulant expectorant in bronchitis, for fumigations, and as incense. SYN: frankincense, thus. [Ar. al, the, + luban, frankincense]

olig- olig-

See oligo-.

oligamnios
oligamnios (ol-i-gam′ne-os)

SYN: oligohydramnios.

oligemia
oligemia (ol-i-ge′me-a)

A deficiency in the amount of blood in the body or any organ or tissue. [oligo- + G. haima, blood]

oligemic
oligemic (ol-i-ge′mik)

Pertaining to or characterized by oligemia.

olighidria
olighidria, oligidria (ol-ig-hid′re-a, -id′re-a)

Scanty perspiration. [oligo- + G. hidros, sweat]

oligo
oligo (ol′i-go)

In molecular genetics, oligonucleotide.

oligo- oligo-, olig-

1. A few, a little; too little, too few. 2. In chemistry, used in contrast to “poly-” in describing polymers; e.g., oligosaccharide. [G. oligos, few]

oligoamnios
oligoamnios (ol′i-go-am′ne-os)

SYN: oligohydramnios. [oligo- + amnion]

oligocholia
oligocholia (ol′i-go-ko′le-a)

A deficient secretion of bile. [oligo- + G. chole, bile]

oligochylia
oligochylia (ol′i-go-ki′le-a)

A deficiency of gastric juice. [oligo- + G. chylos, juice]

oligochymia
oligochymia (ol′i-go-ki′me-a)

A deficiency of chyme. [oligo- + G. chymos, juice]

oligocystic
oligocystic (ol′i-go-sis′tik)

Consisting of only a few cysts, as occasionally observed in certain examples of hydatidiform mole and other lesions that ordinarily have numerous cysts. [oligo- + G. kystis, bladder, cyst]

oligodactyly
oligodactyly, oligodactylia (ol′i-go-dak′ti-le, -dak-til′e-a)

Presence of fewer than five digits on one or more limbs. [oligo- + G. daktylos, finger or toe]

oligodendria
oligodendria (ol′i-go-den′dre-a)

SYN: oligodendroglia.

oligodendroblast
oligodendroblast (ol′i-go-den′dro-blast)

A primitive glial cell that is the normal precursor cell of the oligodendrocyte.

oligodendroblastoma
oligodendroblastoma (ol′i-go-den′dro-blas-to′ma)

Obsolete term for oligodendroglioma. [oligo- + G. dendron, tree, + blastos, germ, + -oma]

oligodendrocyte
oligodendrocyte (ol′i-go-den′dro-sit)

A cell of the oligodendroglia.

oligodendroglia
oligodendroglia (ol′i-go-den-drog′le-a)

One of the three types of glia cells (the other two being macroglia or astrocytes, and microglia) that, together with nerve cells, compose the tissue of the central nervous system. O. cells are characterized by variable numbers of veillike or sheetlike processes that are wrapped each around individual axons to form the myelin sheath of nerve fibers in the central nervous system (compared with Schwann cells in the peripheral nervous system); forms myelin in the central nervous system; accordingly, they are more numerous in white matter than in gray matter. SYN: oligodendria. [oligo- + G. dendron, tree, + glia, glue]

oligodendroglioma
oligodendroglioma (ol′i-go-den′dro-gli-o′ma)

A relatively rare, relatively slowly growing glioma derived from oligodendrocytes that occurs most frequently in the cerebrum of adult persons; the neoplasm is grossly homogeneous, fairly well circumscribed, moderately firm, and somewhat gritty in consistency with interstitial calcification sufficiently dense so as to be detected by x-ray imaging of the skull. Microscopically, an o. is characterized by numerous small, round or ovoid, oligodendroglial cells with small, deeply stained nuclei (rarely observed in mitosis), and palely stained, indistinct cytoplasm; the neoplastic cells are rather uniformly distributed in a sparse, fibrillary stroma with scattered calcific bodies and an often prominent arcuate vasculature. [oligo- + G. dendron, tree, + glia, + -oma]
anaplastic o. an aggressive o. characterized by prominent nuclear pleomorphism, mitoses, and increased cellularity. SYN: pleomorphic o..
pleomorphic o. SYN: anaplastic o..

oligodipsia
oligodipsia (ol′i-go-dip′se-a)

Abnormal lack of thirst. SEE ALSO: hypodipsia. [oligo- + G. dipsa, thirst]

oligodontia
oligodontia (ol′i-go-don′she-a)

SYN: hypodontia. [oligo- + G. odous, tooth]

oligodynamic
oligodynamic (ol′i-go-di-nam′ik)

Active in very small quantity; e.g., the germicidal effect of an exceedingly dilute solution (such as one to one hundred million) of copper in distilled water. [oligo- + G. dynamis, power]

oligogalactia
oligogalactia (ol′i-go-ga-lak′te-a, -she-a)

Slight or scant secretion of milk. [oligo- + G. gala, milk]

oligoglucan-branching glycosyltransferase
oligoglucan-branching glycosyltransferase (ol′i-go-gloo′kan)

SYN: 1,4-α-d-glucan 6-α-d-glucosyltransferase.

oligo-α-1,6-glucosidase
oligo-α-1,6-glucosidase

A glucanohydrolase cleaving α-1,6 links in isomaltose and dextrins produced from starch and glycogen by α-amylase; secreted into the duodenum; a deficiency of this enzyme leads to defects in intestinal digestion of limit dextrins. SEE ALSO: sucrose α-d-glucohydrolase. SYN: isomaltase, limit dextrinase (2) .

oligohydramnios
oligohydramnios (ol′i-go-hi-dram′ne-os)

The presence of an insufficient amount of amniotic fluid (less than 300 mL at term). SYN: hypamnion, hypamnios, oligamnios, oligoamnios. [oligo- + G. hydor, water, + amnion]

oligohydruria
oligohydruria (ol′i-go-hi-droo′re-a)

Obsolete term for excretion of small quantities of urine, as seen in dehydration. [oligo- + G. hydor, water, + ouron, urine]

oligolecithal
oligolecithal (ol′i-go-les′i-thal)

Having little yolk; denoting an egg in which there is only a little scattered deutoplasm. [oligo- + G. lekithos, yolk]

oligomenorrhea
oligomenorrhea (ol′i-go-men-o-re′a)

Scanty menstruation. [oligo- + menorrhea]

oligomer
oligomer (ol′i-go-mer)

A polymer containing only a few repeating units, a “few” generally considered as fewer than 20.

oligomorphic
oligomorphic (ol′-i-go-mor′fik)

Presenting few changes of form; not polymorphic. [oligo- + G. morphe, form]

oligonephronic
oligonephronic (ol′i-go-nef-ron′ik)

Characterized by a reduced number of nephrons.

oligonucleotide
oligonucleotide (ol′i-go-noo′kle-o-tid)

A compound made up of the condensation of a small number (typically fewer than 20) of nucleotides. Cf.:polynucleotide.

oligopepsia
oligopepsia (ol′i-go-pep′se-a)

SYN: hypopepsia.

oligopeptide
oligopeptide (ol′igo-pep-tid)

A peptide whose molecule contains a few amino acid residues up to about 20.

oligophrenia
oligophrenia (ol′i-go-fre′ne-a)

SYN: mental retardation.
phenylpyruvate o. SYN: phenylketonuria.

oligoplastic
oligoplastic (ol′i-go-plas′tik)

Deficient in reparative power. [oligo- + G. plasso, to form]

oligopnea
oligopnea (ol′i-gop-ne′a, -gop′ne-a)

SYN: hypopnea. [oligo- + G. pnoe, breath]

oligoptyalism
oligoptyalism (ol′i-go-ti′a-lizm, ol′i-gop-ti′)

A scanty secretion of saliva. SYN: oligosialia. [oligo- + G. ptyalon, saliva]

oligoria
oligoria (ol-i-gor′e-a)

A rarely used term for an abnormal indifference toward or dislike of persons or things. [G. o., negligence, slight esteem, fr. oligos, little, + ora, care, regard]

oligosaccharide
oligosaccharide (ol′i-go-sak′a-rid)

A compound made up of the condensation of a small number of monosaccharide units. Cf.:polysaccharide.

oligosialia
oligosialia (ol′i-go-si-a′le-a)

SYN: oligoptyalism. [oligo- + G. sialon, saliva]

oligospermia
oligospermia, oligospermatism (ol-i-go-sper′me-a, -ma-tizm)

SYN: oligozoospermia. [oligo- + G. sperma, seed]

oligosymptomatic
oligosymptomatic (ol′i-go-simp-to-mat′ik)

Having few or minor symptoms.

oligosynaptic
oligosynaptic (ol′i-go-si-nap′tik)

Referring to neural conduction pathways that are interrupted by only a few synaptic junctions, i.e., made up of a sequence of only few nerve cells, in contrast to polysynaptic pathways. SYN: paucisynaptic.

oligothymia
oligothymia (ol′i-go-thi′me-a)

Rarely used term for a poverty or loss of affect. [oligo- + -thymia]

oligotrichia
oligotrichia (ol′i-go-trik′e-a)

SYN: hypotrichosis.

oligotrichosis
oligotrichosis (ol′i-go-tri-ko′sis)

SYN: hypotrichosis.

oligotrophia
oligotrophia, oligotrophy (ol′i-go-tro′fe-a, -got′ro-fe)

Deficient nutrition. [oligo- + G. trophe, nourishment]

oligozoospermatism
oligozoospermatism (ol′i-go-zo′o-sper′ma-tizm)

SYN: oligozoospermia. [oligo- + G. zoon, animal, + sperma, seed]

oligozoospermia
oligozoospermia (ol′i-go-zo′o-sperm′e-a)

A subnormal concentration of spermatozoa in the penile ejaculate. SYN: oligospermia, oligospermatism, oligozoospermatism. [oligo- + G. zoos, living, + sperma, seed, semen, + -ia]

oliguria
oliguria (ol-i-goo′re-a)

Scanty urine production. [oligo- + G. ouron, urine]

oliva
oliva, pl .olivae (o-li′va) [TA]

A smooth oval prominence of the ventrolateral surface of the medulla oblongata lateral to the pyramidal tract, corresponding to the inferior olivary nucleus. SYN: corpus olivare, inferior olive, olivary body, olivary eminence, olive (1) . [L.]
o. inferior the o..
o. superior SYN: dorsal nucleus of trapezoid body.

olivary
olivary (ol′i-var-e)

1. Relating to the oliva. 2. Relating to or shaped like an olive.

olive
olive (ol′iv)

1. SYN: oliva. 2. Common name for a tree of the genus Olea (family Oleaceae) or its fruit. [L. oliva]
inferior o. SYN: oliva.
superior o. SYN: dorsal nucleus of trapezoid body.

olive oil
olive oil

See under oil.

olivifugal
olivifugal (ol′i-vif′u-gal)

In a direction away from the olive. [oliva + L. fugio, to flee]

olivipetal
olivipetal (ol′i-vip′e-tal)

In a direction toward the olive. [oliva + L. peto, to seek]

olivocochlear
olivocochlear (ol′i-vo-kok′le-ar)

See o. tract.

olivopontocerebellar
olivopontocerebellar (ol′i-vo-pon′to-sar-e-bel′ar)

Relating to the olivary nucleus, basis pontis, and cerebellum.

Ollendorf
Ollendorf

Helene, German dermatologist, fl. 1928. See Buschke-O. syndrome.

Ollier
Ollier

Louis X.E.L., French surgeon, 1830–1900. See O. graft, O. disease, O. theory, O.-Thiersch graft.

Olmsted
Olmsted

H.C., 20th century U.S. pediatrician. See O. syndrome.

-ology -ology

See -logia.

ololiuqui
ololiuqui (o-lo-lu′ke)

A hallucinogen used in ceremonies by the Aztec Indians in Mexico; contains ergot alkaloids and derivatives of lysergic acid. SEE ALSO: Rivea corymbosa, Ipomoea rubrocoerulea praecox.

olophonia
olophonia (ol′o-fo′ne-a)

Impaired speech caused by an anatomical defect in the vocal organs. [G. oloos, destroyed, lost, + phone, voice]

Olszewski
Olszewski

Jerzy, Polish-Canadian neuropathologist, 1913–1964. See Steele-Richardson-O. disease, Steele-Richardson-O. syndrome.

-oma -oma

A tumor or neoplasm. [G. -oma, suffix forming nouns from some verb stems]

-omata -omata

Plural of -oma.

Ombrédanne
Ombrédanne

Louis, French surgeon, 1871–1956. See O. operation.

ombrophobia
ombrophobia (om-bro-fo′be-a)

Morbid fear of rain. [G. ombros, rainstorm, + phobos, fear]

Omenn
Omenn

Gilbert S., U.S. internist, *1941. See O. syndrome.

omental
omental (o-men′tal)

Relating to the omentum. SYN: epiploic.

omentectomy
omentectomy (o-men-tek′to-me)

Resection or excision of the omentum. SYN: omentumectomy. [omentum + G. ektome, excision]

omentitis
omentitis (o-men-ti′tis)

Peritonitis involving the omentum. [L. omentum + G. -itis, inflammation]

omento- omento-, oment-

The omentum. SEE ALSO: epiplo-. [L. omentum]

omentofixation
omentofixation (o-men′to-fik-sa′shun)

SYN: omentopexy.

omentopexy
omentopexy (o-men′to-pek-se)

1. Suture of the greater omentum to the abdominal wall to induce collateral portal circulation. 2. Suture of the omentum to another organ to increase arterial circulation. SEE ALSO: omentoplasty. SYN: omentofixation. [omento- + G. pexis, fixation]

omentoplasty
omentoplasty (o-men′to-plas-te)

Use of greater omentum to cover or fill a defect, augment arterial or portal venous circulation, absorb effusions, or increase lymphatic drainage. SEE ALSO: omentopexy. [omento- + G. plastos, formed]

omentorrhaphy
omentorrhaphy (o-men-tor′a-fe)

Suture of an opening in the omentum. [omento- + G. rhaphe, suture]

omentovolvulus
omentovolvulus (o-men-to-vol′vu-lus)

Twisting of the omentum on a pedicile.

omentulum
omentulum (o-men′tu-lum)

SYN: lesser omentum. [Mod. L. dim. of omentum]

omentum
omentum, pl .omenta (o-men′tum, -ta) [TA]

A fold of peritoneum passing from the stomach to another abdominal organ. [L. the membrane that encloses the bowels]
gastrocolic o. SYN: greater o..
gastrohepatic o. SYN: lesser o..
gastrosplenic o. SYN: gastrosplenic ligament.
greater o. [TA] an areolar, four-layer peritoneal fold, formed by the double-layer dorsal mesentery of the stomach (dorsal mesogastrium) descending from the greater curvature of the stomach to fold under on itself and ascend to the transverse colon; the descending and ascending portions fuse, obliterating the inferior recess of the omental bursa, resulting in the four-layer structure that usually hangs over the anterior aspect of the intestines like an apron; components include the following peritoneal ligaments: gastrophrenic, gastrosplenic, splenorenal, and gastrocolic. SYN: o. majus [TA] , caul (2) , cowl, epiploon, gastrocolic o., pileus, velum (3) .
lesser o. [TA] a thin, double-layer peritoneal fold formed by the ventral mesentery of the stomach (ventral mesogastrium) passing from the lesser curvature of the stomach and upper border to the proximal duodenum (2 cm distal to the pylorus) to the liver (margins of the porta hepatis and into the depth of the fissure of the ductus venosus); major subcomponents include the hepatogastric ligament (main sheetlike portion) and the hepatoduodenal ligament (thickened free right border, which encloses the hepatic artery, portal vein, and common bile duct. SYN: o. minus [TA] , gastrohepatic o., omentulum.
o. majus [TA] SYN: greater o..
o. minus [TA] SYN: lesser o..

omentumectomy
omentumectomy (o-men-tu-mek′to-me)

SYN: omentectomy.

omeprazole
omeprazole (o-me′pra-zol)

A drug that blocks the transport of hydrogen ions into the stomach and is used as an antiulcerative and in treatment of Zollinger-Ellison syndrome.

Ommaya
Ommaya

Ayub K., U.S. neurosurgeon, *1930. See O. reservoir.

omn. hor.
omn. hor.

Abbreviation for L. o., every hour.

omnipotence of thought
omnipotence of thought (om-nip′o-tens)

A childish or magical thought process whereby instantaneous gratification of fantasies and wishes is believed to be imminent.

omnivorous
omnivorous (om-niv′o-rus)

Living on food of all kinds, upon both animal and vegetable food. [L. omnis, all, + voro, to eat]

omo- omo-

The shoulder (sometimes including the upper arm). [G. omos, shoulder]

omoclavicular
omoclavicular (o′mo-kla-vik′u-lar)

Relating to the shoulder and the clavicle; denoting an anomalous muscle attached to the coracoid process or upper edge of the scapula and to the clavicle.

omohyoid
omohyoid (o-mo-hi′oyd)

SYN: o. (muscle).

omophagia
omophagia (o-mo-fa′je-a)

The eating of raw food, especially of raw flesh. [G. omos, raw, + phago, to eat]

omothyroid
omothyroid (o-mo-thi′royd)

Denoting a band of muscular fibers passing between the superior cornu of the thyroid cartilage and the omohyoid muscle.

OMP
OMP

Abbreviation for oligo-N-methylmorpholinium propylene oxide; orotidylic acid; orotidylate; orotidine 5′-monophosphate.

OMPA
OMPA

Abbreviation for octamethyl pyrophosphoramide.

OMP decarboxylase
OMP decarboxylase

SYN: orotidylic acid decarboxylase.

omphal- omphal-, omphalo-

The umbilicus, the navel. [G. omphalos, navel (umbilicus)]

omphalectomy
omphalectomy (om-fa-lek′to-me)

Excision of the umbilicus or of a neoplasm connected with it. [omphal- + G. ektome, excision]

omphalelcosis
omphalelcosis (om′fal-el-ko′sis)

Ulceration at the umbilicus. [omphal- + G. helkosis, ulceration]

omphalic
omphalic (om-fal′ik)

SYN: umbilical. [G. omphalos, umbilicus]

omphalitis
omphalitis (om-fa-li′tis)

Inflammation of the umbilicus and surrounding parts.

omphalo- omphalo-

See omphal-.

omphaloangiopagus
omphaloangiopagus (om′fa-lo-an-je-op′a-gus)

Unequal conjoined twins in which the parasite derives its blood supply from the placenta of the autosite. See conjoined twins, under twin. SYN: allantoidoangiopagus. [omphalo- + G. angeion, vessel, + pagos, something fixed]

omphalocele
omphalocele (om′fal-o-sel, om′fa-lo-)

Congenital herniation of viscera into the base of the umbilical cord, with a covering membranous sac of peritoneum-amnion. The umbilical cord is inserted into the sac here, in contradistinction to its attachment in gastroschisis. SEE ALSO: umbilical hernia. SYN: amniocele, exomphalos (3) , exumbilication (3) . [omphalo- + G. kele, hernia]

omphaloenteric
omphaloenteric (om′fa-lo-en-tar-ik)

Relating to the umbilicus and the intestine.

omphalomesenteric
omphalomesenteric (om′fa-lo-mez-en-tar′ik)

1. Term denoting relationship of the midgut to the yolk sac. As the head and tail folds of the embryo continue to form, this relationship is diminished and is represented by a narrow yolk stalk or vitelline duct. 2. Relating to the vitelline duct.

omphalopagus
omphalopagus (om′fa-lop′a-gus)

Conjoined twins united at their umbilical regions. See conjoined twins, under twin. SYN: monomphalus. [omphalo- + G. pagos, something fixed]

omphalophlebitis
omphalophlebitis (om′fa-lo-fle-bi′tis)

Inflammation of the umbilical veins. [omphalo- + G. phleps, vein, + -itis, inflammation]

omphalorrhagia
omphalorrhagia (om′fa-lo-ra′je-a)

Bleeding from the umbilicus. [omphalo- + G. rhegnymi, to burst forth]

omphalorrhea
omphalorrhea (om′fa-lo-re′a)

A serous discharge from the umbilicus. [omphalo- + G. rhoia, flow]

omphalorrhexis
omphalorrhexis (om′fa-lo-rek′sis)

Rupture of the umbilical cord during childbirth. [omphalo- + G. rhexis, rupture]

omphalos
omphalos (om′fa-los)

Rarely used term for umbilicus. [G. navel]

omphalosite
omphalosite (om′fa-lo-sit)

Underdeveloped twin of allantoidangiopagous twin; joined by umbilical vessels. SYN: placental parasitic twin. [omphalo- + G. sitos, food]

omphalospinous
omphalospinous (om′fa-lo-spi′nus)

Denoting a line connecting the umbilicus and the anterior superior spine of the ilium, on which lies the McBurney point.

omphalotomy
omphalotomy (om-fa-lot′o-me)

Cutting of the umbilical cord at birth. [omphalo- + G. tome, incision]

omphalotripsy
omphalotripsy (om′fa-lo-trip′se)

Crushing, instead of cutting, the umbilical cord after childbirth. [omphalo- + G. tripsis, a rubbing]

omphalovesical
omphalovesical (om′fa-lo-ves′i-kal)

SYN: vesicoumbilical.

omphalus
omphalus (om′fa-lus)

Rarely used term for umbilicus. [G. omphalos, navel]

OMP pyrophosphorylase
OMP pyrophosphorylase

SYN: orotate phosphoribosyltransferase.

oncho- oncho-

See onco-.

Onchocerca
Onchocerca (ong-ko-ser′ka)

A genus of elongated filariform nematodes (family Onchocercidae) that inhabit the connective tissue of their hosts, usually within firm nodules in which these parasites are coiled and entangled. SYN: Oncocerca. [G. onkos, a barb, + kerkos, tail]
Onchocerca volvulus the blinding nodular worm, a species that causes onchocerciasis.

onchocerciasis
onchocerciasis (ong′ko-ser-ki′a-sis)

Infection with Onchocerca (especially O. volvulus, a filarial nematode transmitted from person to person by black flies of the genus Simulium), marked by nodular swellings forming a fibrous cyst enveloping the coiled parasites (onchocercoma); microfilariae move freely out of the nodule and escape into the intercellular lymph in the dermis. Dermatologic changes often develop, especially in Africa, resulting in intense pruritus, scaly or lichenoid skin, depigmentation, and destruction of elastic fibers. Most important are the ocular complications that may develop after a long chronic course, with blindness frequently occurring in advanced cases, caused by the presence of living or dead microfilariae seen by slitlamp biomicroscopy. SYN: blinding disease, onchocercosis, volvulosis.
ocular o. ocular complications, such as keratitis, iridocyclitis, or retrobulbar neuritis, caused by the microfilariae of Onchocerca volvulus. SYN: river blindness.

onchocercid
onchocercid (ong-ko-ser′kid)

Common name for members of the family Onchocercidae.

Onchocercidae
Onchocercidae (ong-ko-ser′ki-de)

A family of nematode parasites (superfamily Filarioidea) characterized by production of microfilariae; it includes the genera Onchocerca, Wuchereria, Brugia, Loa, and Mansonella.

onchocercoma
onchocercoma (on′ko-ser-ko′ma)

Nodule containing adult worms of Onchocera volvulus. [Onchocerca, taxonomic term, + -oma]

onchocercosis
onchocercosis (ong′ko-ser-ko′sis)

SYN: onchocerciasis.

onco- onco-, oncho-

A tumor. [G. onkos, bulk, mass]

Oncocerca
Oncocerca (ong-ko-ser′ka)

SYN: Onchocerca.

oncocyte
oncocyte (ong′ko-sit)

A large, granular, acidophilic tumor cell containing numerous mitochondria; a neoplastic oxyphil cell. [onco- + G. kytos, cell]

oncocytoma
oncocytoma (ong′ko-si-to′ma)

A glandular tumor composed of large cells with cytoplasm that is granular and eosinophilic because of the presence of abundant mitochondria; occurs uncommonly in the kidney, salivary glands, and endocrine glands. SYN: oxyphil adenoma. [onco- + G. kytos, cell, + -oma, tumor]

oncofetal
oncofetal (ong-ko-fe′tal)

Relating to tumor-associated substances present in fetal tissue, as o. antigens.

oncogene
oncogene (ong′ko-jen)

1. Any of a family of genes that normally encode proteins involved in cell growth or regulation (e.g., protein kinases, GTPases, nuclear proteins, growth factors) but that may foster malignant processes if mutated or activated by contact with retroviruses. Identified oncongenes include ras, originally noted in bladder tumors, and p53, a mutated version of a gene on chromosome 17 that has been shown to be involved in more than half of all human cancers. Oncogenes can work in concert to produce cancer, and their action may be exacerbated by retroviruses, jumping genes, or inherited genetic mutations. SEE ALSO: tumor suppressor gene. 2. A gene found in certain DNA tumor viruses. It is required for viral replication. SYN: transforming gene. [onco- + gene] Genes whose mutations can permit or induce uncontrolled cellular proliferation and malignant change are of 2 types: protooncogenes and tumor suppressor genes (antioncogenes). Protooncogenes encode proteins that stimulate DNA synthesis and cell division, including peptide growth factors and their cellular membrane receptors; second-messenger cascade proteins, which transmit information from cell membrane to nucleus; and nuclear transcription factors, which control gene expression by binding to DNA. Conversion of a protooncogene to an o. by amplification, translocation, or point mutation can lead to unrestrained cellular proliferation and malignant change. Only 1 copy (allele) of a protooncogene need undergo mutation to induce tumor formation. Protooncogenes are not involved in inherited cancer syndromes, with the exception of the RET protooncogene in multiple endocrine neoplasia. Tumor suppressor genes (antioncogenes), which encode proteins that normally serve to restrain cell proliferation, can be inactivated by point mutation, deletion, or loss of expression. An inherited mutation in 1 copy of a tumor suppressor gene is the basis of most familial predispositions to cancer. Malignant cellular proliferation does not occur until the remaining, functional copy of the gene is inactivated by mutation or by deletion of part or all of its chromosome. In a person born with 2 normal copies of a tumor suppressor gene, both must be inactivated by mutation before tumor formation occurs. BRCA1 and BRCA2, which are associated with familial early-onset breast cancer and ovarian cancer, are tumor suppressor genes.
ras o. point mutations first described in rat sarcoma cells that can be shown to have transforming activity in culture as well as in tumorigenesis models in mice; the ras gene family is composed of three closely related genes on three different chromosomes; abnormalities have been identified in a variety of human tumors.

oncogenesis
oncogenesis (ong-ko-jen′e-sis)

Origin and growth of a neoplasm. [onco- + G. genesis, production]

oncogenic
oncogenic (ong-ko-jen′ik)

SYN: oncogenous.

oncogenous
oncogenous (ong-koj′e-nus)

Causing, inducing, or being suitable for the formation and development of a neoplasm. SYN: oncogenic.

oncograph
oncograph (ong′ko-graf)

A recording oncometer, or the recording portion of an oncometer. [onco- + G. graphe, a record]

oncography
oncography (ong′kog′ra-fe)

Graphic representation, by means of a special apparatus, of the size and configuration of an organ.

oncoides
oncoides (ong-koy′dez)

Intumescence or turgescence. [onco- + G. eidos, resemblance]

oncologist
oncologist (ong-kol′o-jist)

A specialist in oncology.
radiation o. SYN: radiotherapist.

oncology
oncology (ong-kol′o-je)

The study or science dealing with the physical, chemical, and biologic properties and features of neoplasms, including causation, pathogenesis, and treatment. [onco- + G. logos, study]
radiation o. 1. the medical specialty concerned with the use of ionizing radiation in the treatment of disease; 2. the medical specialty of radiation therapy; 3. the use of radiation in the treatment of neoplasms. SYN: radiotherapy, therapeutic radiology.

oncolysis
oncolysis (ong-kol′i-sis)

Destruction of a neoplasm; sometimes used with reference to the reduction of any swelling or mass. [onco- + G. lysis, dissolution]

oncolytic
oncolytic (ong-ko-lit′ik)

Pertaining to, characterized by, or causing oncolysis.

Oncomelania
Oncomelania (ong′ko-me-la′ni-a)

A medically important genus of amphibious freshwater operculate snails of the family Hydrobiidae (subfamily Hydrobiinae; subclass Prosobranchiata). In Asia, several subspecies of O. hupensis serve as intermediate hosts of the oriental blood fluke, Schistosoma japonicum. [onco- + G. melas (melan-), black]

oncometer
oncometer (ong-kom′e-ter)

1. An instrument for measuring the size and configuration of the kidneys and other organs. 2. The measuring, as distinguished from the recording part of the oncograph. [onco- + G. metron, measure]

oncometric
oncometric (ong-ko-met′rik)

Relating to oncometry.

oncometry
oncometry (ong-kom′e-tre)

Measurement of the size of an organ.

oncosis
oncosis (ong-ko′sis)

A condition characterized by the formation of one or more neoplasms or tumors. [G. onkosis, swelling, fr. onkos, bulk, mass]

oncosphere
oncosphere (ong′-ko-sfer)

SYN: hexacanth. [onco- + G. sphaira, sphere]

oncostatin M
oncostatin M (onk′o-stat′in em)

An interleukin 6. [onco- + -stat + -in]

oncotherapy
oncotherapy (ong-ko-thar′a-pe)

Treatment of tumors.

oncotic
oncotic (ong-kot′ik)

Relating to or caused by edema or any swelling (oncosis).

oncotomy
oncotomy (ong-kot′o-me)

Rarely used term for incision of an abscess, cyst, or other tumor. [onco- + G. tome, incision]

oncotropic
oncotropic (ong′ko-trop′ik)

Manifesting a special affinity for neoplasms or neoplastic cells. [onco- + G. trope, a turning]

Oncovirinae
Oncovirinae (ong-ko-vir′i-ne)

Term formerly used to designate a now obsolete subfamily of viruses (family Retroviridae) composed of the RNA tumor viruses that contain two identical plus-stranded RNA molecules. Subgroups are based on antigenicity, host range, and kind of malignancy induced (avian, feline, hamster, or murine leukemia-sarcoma complex; murine mammary tumor virus; primate oncoviruses). Like other retroviruses, they contain RNA-dependent DNA polymerases (reverse transcriptases). An important aspect of these viruses seems to be use of viral reverse transcriptase to make DNA that can be integrated into the DNA of the host cell and will replicate along with cellular DNA. SEE ALSO: retrovirus.

oncovirus
oncovirus (ong′ko-vi′rus)

Term formerly used to describe any virus of the subfamily Oncovirinae. SEE ALSO: oncogenic virus.

ondansetron
ondansetron (on-dan′se-tron)

A serotonin 5-HT₃ receptor antagonist used as an antiemetic, particularly in patients undergoing chemotherapy or radiation treatment for cancer.

Ondine
Ondine

German mythological character. See O. curse.

-one -one

Suffix indicating a ketone (–CO–) group.

oneiric
oneiric (o-ni′rik)

1. Pertaining to dreams. 2. Pertaining to the clinical state of oneirophrenia. SYN: oniric. [G. oneiros, dream]

oneirism
oneirism (o-ni′rizm)

A waking dream state. [G. oneiros, dream]

oneirocritical
oneirocritical (o-ni-ro-krit′i-kal)

Rarely used term pertaining to the logic of dreams. [G. oneiros, dream, + kritikos, skilled in judgment]

oneirodynia
oneirodynia (o-ni-ro-din′e-a)

Rarely used term for an unpleasant or painful dream. [G. oneiros, dream, + odyne, pain]
o. activa SYN: somnambulism (1) .

oneirology
oneirology (o-ni-rol′o-je)

The study of dreams and their content. [G. oneiros, dream, + logos, study]

oneirophrenia
oneirophrenia (o-ni-ro-fre′ne-a)

A rarely used term for a state in which hallucinations occur, caused by such conditions as prolonged deprivation of sleep, sensory isolation, and a variety of drugs. [G. oneiros, dream, + phren, mind]

oniomania
oniomania (o′ne-o-ma′ne-a)

Rarely used term for the morbidly exaggerated need or urge to buy beyond the realistic needs of the individual. [G. onios, for sale, + mania, insanity]

oniric
oniric (o-ni′rik)

SYN: oneiric.

-onium -onium

Suffix indicating a positively charged radical; e.g., ammonium, NH₄⁺.

onko- onko-

See onco-.

onlay
onlay (on′la)

1. A metal (usually gold) cast restoration of the occlusal surface of a posterior tooth or the lingual surface of an anterior tooth, the entire surface of which is in dentin without side walls; retention in the anterior tooth is by pins and in the posterior by pins and/or boxes in retentive grooves in the buccal and lingual walls. 2. A graft applied on the exterior of a bone. 3. A graft applied to skin in native urethra in hypospadias or stricture repair.

Onodi
Onodi

Adolf, Hungarian laryngologist, 1857–1920. See O. cell.

onomatomania
onomatomania (on′o-mat-o-ma′ne-a)

An abnormal impulse to dwell upon certain words and their supposed significance, or to frantically try to recall a particular word. [G. onoma, name, + mania, frenzy]

onomatophobia
onomatophobia (on′o-mat-o-fo′be-a)

Abnormal dread of certain words or names because of their supposed significance. [G. onoma, name, + phobos, fear]

onomatopoiesis
onomatopoiesis (on′o-mat′o-poy-e′sis)

The making of a name or word, especially to express or imitate a natural sound ( e.g., hiss, crash, boom); in psychiatry, the tendency to make new words of this type is said to characterize some persons with schizophrenia. SEE ALSO: neologism. [G. onoma, name, + poiesis, making]

ontogenesis
ontogenesis (on-to-jen′e-sis)

SYN: ontogeny.

ontogenetic
ontogenetic, ontogenic (on′to-je-net′ik, -jen′ik)

Relating to ontogeny.

ontogeny
ontogeny (on-toj′e-ne)

Development of the individual, as distinguished from phylogeny, which is evolutionary development of the species. SYN: ontogenesis. [G. on, being, + genesis, origin]

ontology
ontology (on-tol′o-je)

A traditional branch of metaphysics that deals with problems of being, existence, inner nature, meaning, etc. It is fundamental to problems involving normality and disease, individuality, responsibility, and the analysis of values. In recent years, it has been slowly assuming a place as a branch of medicine proper.

Onufrowicz
Onufrowicz

Wladislaus, Swiss anatomist, 1836–1900. See Onuf nucleus.

onyalai
onyalai (on-i-al′a)

An acute disease affecting natives of Central Africa, characterized by bloody vesicles of the mouth and other mucous surfaces, hematuria, and melena; defective nutrition may be the cause. SYN: akembe, kafindo.

onych- onych-

See onycho-.

onychalgia
onychalgia (on-i-kal′je-a)

Pain in the nails. [onycho- + G. algos, pain]

onychatrophia
onychatrophia, onychatrophy (on′i-ka-tro′fe-a, on-ik-at′ro-fe)

Atrophy of the nails. [onycho- + G. atrophia, atrophy]

onychauxis
onychauxis (on-i-kawk′sis)

Marked overgrowth of the fingernails or toenails. [onycho- + G. auxe, increase]

onychectomy
onychectomy (on-i-kek′to-me)

Ablation of a toenail or fingernail. [onycho- + G. ektome, excision]

onychia
onychia (o-nik′e-a)

Inflammation of the matrix of the nail. [onycho- + G. -ia, condition]
o. maligna acute o. occurring spontaneously in debilitated patients, or in response to slight trauma.
o. sicca a condition characterized by brittle nails.

onycho- onycho-, onych-

A finger nail, a toenail. [G. onyx, nail]

onychoclasis
onychoclasis (on-i-kok′la-sis)

Breaking of the nails. [onycho- + G. klasis, breaking]

onychocryptosis
onychocryptosis (on′i-ko-krip-to′sis)

SYN: ingrown nail. [onycho- + G. krypto, to conceal]

onychodystrophy
onychodystrophy (on′i-ko-dis′tro-fe)

Dystrophic changes in the nails occurring as a congenital defect or due to any illness or injury that may cause a malformed nail. [onycho- + G. dys-, bad, + trophe, nourishment]

onychograph
onychograph (on′i-ko-graf)

An instrument for recording the capillary blood pressure as shown by the circulation under the nail. [onycho- + G. grapho, to write]

onychogryposis
onychogryposis (on′i-ko-gri-po′sis)

Enlargement with increased thickening and curvature of the fingernails or toenails. [onycho- + G. gryposis, a curvature]

onychoheterotopia
onychoheterotopia (on′i-ko-het-er-o-to′pe-a)

Abnormal placement of nails.

onychoid
onychoid (on′i-koyd)

Resembling a fingernail in structure or form. [onycho- + G. eidos, resemblance]

onychology
onychology (on-i-kol′o-je)

Study of the nails. [onycho- + G. logos, treatise]

onycholysis
onycholysis (on-i-kol′i-sis)

Loosening of the nails, beginning at the free border, and usually incomplete. [onycho- + G. lysis, loosening]

onychomadesis
onychomadesis (on′i-ko-ma-de′sis)

Complete shedding of the nails, usually associated with systemic disease. [onycho- + G. madesis, a growing bald, fr. madao, to be moist, (of hair) fall off]

onychomalacia
onychomalacia (on′i-ko-ma-la′she-a)

Abnormal softness of the nails. [onycho- + G. malakia, softness]

onychomycosis
onychomycosis (on′i-ko-mi-ko′sis)

Very common fungus infections of the nails, causing thickening, roughness, and splitting, often caused by Trichophyton rubrum or T. mentagrophytes, Candida, and occasionally molds. SYN: ringworm of nails. [onycho- + G. mykes, fungus, + -osis, condition]

onychopathology
onychopathology (on′i-ko-pa-thol′o-je)

Study of diseases of the nails.

onychopathy
onychopathy (on-i-kop′a-the)

Any disease of the nails. SYN: onychosis. [onycho- + G. pathos, suffering]

onychophagy
onychophagy, onychophagia (on-i-kof′a-je, on′i-ko-fa′je-a)

Habitual nailbiting. [onycho- + G. phago, to eat]

onychophosis
onychophosis (on′i-ko-fo′sis)

A growth of horny epithelium in the nail bed. [onycho- + G. phos, light, + -osis, condition]

onychoptosis
onychoptosis (on′i-kop-to′sis)

Falling off of the nails. [onycho- + G. ptosis, a falling]

onychorrhexis
onychorrhexis (on′i-ko-rek′sis)

Abnormal brittleness of the nails with splitting of the free edge. [onycho- + G. rhexis, a breaking]

onychoschizia
onychoschizia (on′i-ko-skiz′e-a)

Splitting of the nails in layers. [onycho- + G. schizo, to divide, + -ia, condition]

onychosis
onychosis (on-i-ko′sis)

SYN: onychopathy.

onychostroma
onychostroma (on′i-ko-stro′ma)

SYN: nail matrix. [onycho- + G. stroma, bedding]

onychotillomania
onychotillomania (on′i-kot′i-lo-ma′ne-a)

A tendency to pick at the nails. [onycho- + G. tillo, to pluck, + mania, insanity]

onychotomy
onychotomy (on-i-kot′o-me)

Incision into a toenail or fingernail. [onycho- + G. tome, cutting]

onychotrophy
onychotrophy (on-i-kot′ro-fe)

Nutrition of the nails. [onycho- + G. trophe, nourishment]

onyx
onyx (on′iks)

SYN: nail (1) . [G. nail]

oo- oo-

Egg, ovary. SEE ALSO: oophor-, ovario-, ovi-, ovo-. [G. oon, egg]

oocyesis
oocyesis (o-o-si-e′sis)

SYN: ovarian pregnancy. [G. oon, egg, + kyesis, pregnancy]

oocyst
oocyst (o′o-sist)

The encysted form of the fertilized macrogamete, or zygote, in coccidian Sporozoea in which sporogonic multiplication occurs; results in the formation of sporozoites, infectious agents for the next stage of the sporozoan life cycle. [G. oon, egg, + kystis, bladder]

oocyte
oocyte (o′o-sit)

The immature ovum. SYN: ovocyte. [G. oon, egg, + kytos, a hollow (cell)]
primary o. an o. during its growth phase and before it completes the first maturation division.
secondary o. an o. in which the first meiotic division is completed; the second meiotic division usually stops short of completion unless fertilization occurs.

oogenesis
oogenesis (o-o-jen′e-sis)

Process of formation and development of the ovum. SYN: ovigenesis, ovogenesis. [G. oon, egg, + genesis, origin]

oogenetic
oogenetic (o-o-je-net′ik)

Producing ova. SYN: oogenic, oogenous, ovigenetic, ovigenic, ovigenous.

oogenic
oogenic, oogenous (o-o-jen′ik, o-oj′e-nus)

SYN: oogenetic.

oogonium
oogonium, pl .oogonia (o-o-go′ne-um, -a)

1. Primitive germ cells; proliferate by mitotic division. All oogonia develop into primary oocytes prior to birth; no oogonia are present after birth. 2. In fungi, the female gametangium bearing one or more oospores. [G. oon, egg, + gone, generation]

ookinesis
ookinesis, ookinesia (o′o-ki-ne′sis, -ze-a)

Chromosomal movements of the egg during maturation and fertilization. [G. oon, egg, + kinesis, movement]

ookinete
ookinete (o′o-ki-ne′t, -ki′ne′t)

The motile zygote of the malarial organism that penetrates the mosquito stomach to form an oocyst under the outer gut lining; the contents of the oocyst subsequently divide to produce numerous sporozoites. SYN: vermicule (2) . [G. oon, egg, + kinetos, motile]

oolemma
oolemma (o-o-lem′a)

Plasma membrane of the oocyte. [G. oon, egg, + lemma, sheath]

oomycosis
oomycosis (o′o-mi-ko′sis)

A mycosis caused by fungi belonging to the class Oomycetes; e.g., rhinosporidiosis.

oophagia
oophagia, oophagy (o-o-fa′je-a, o-of′a-je)

The habitual eating of eggs; subsisting largely on eggs. [G. oon, egg, + phago, to eat]

oophor- oophor-, oophoro-

The ovary. SEE ALSO: oo-, ovario-. [Mod. L. oophoron, ovary, fr. G. oophoros, egg-bearing]

oophoralgia
oophoralgia (o-of-or-al′je-a)

SYN: ovarialgia. [oophor- + G. algos, pain]

oophorectomy
oophorectomy (o-of-or-ek′to-me)

SYN: ovariectomy. [G. oon, egg, + phoros, bearing, + ektome, excision]

oophoritis
oophoritis (o-of-or-i′tis)

Inflammation of an ovary. SYN: ovaritis. [G. oon, egg, + phoros, a bearing, + -itis, inflammation]

oophoro- oophoro-

See oophor-.

oophorocystectomy
oophorocystectomy (o-of′or-o-sis-tek′to-me)

Excision of an ovarian cyst.

oophorocystosis
oophorocystosis (o-of′or-o-sis-to′sis)

Ovarian cyst formation.

oophoron
oophoron (o-of′or-on)

Rarely used term for ovary. [G. oon, egg, + phoros, bearing]

oophoropathy
oophoropathy (o-of-or-op′a-the)

SYN: ovariopathy.

oophoropexy
oophoropexy (o-of′or-o-pek-se)

Surgical fixation or suspension of an ovary. [oophoro- + G. pexis, fixation]

oophoroplasty
oophoroplasty (o-of′or-o-plas-te)

Plastic operation upon an ovary. [oophoro- + G. plastos, formed, shaped]

oophororrhaphy
oophororrhaphy (o-of-o-ror′a-fe)

Suspension of the ovary by attachment to the pelvic wall. [oophoro- + G. rhaphe, suture]

oophorosalpingectomy
oophorosalpingectomy (o-of′or-o-sal-pin-jek′to-me)

SYN: ovariosalpingectomy.

oophorosalpingitis
oophorosalpingitis (o-of′or-o-sal-pin-ji′tis)

SYN: ovariosalpingitis. [oophoro- + salpingitis]

oophorotomy
oophorotomy (o-of-or-ot′o-me)

SYN: ovariotomy. [oophoro- + G. tome, incision]

oophorrhagia
oophorrhagia (o-of-or-ra′je-a)

Ovarian hemorrhage. [oophoro- + G. rhegnymi, to burst forth]

ooplasm
ooplasm (o′o-plazm)

Protoplasmic portion of the ovum. [G. oon, egg, + plasma, a thing formed]

oosome
oosome (o′o-som)

A cytoplasmic body in the ovum that passes into the germ cell. [G. oon, egg + soma, body]

oosporangium
oosporangium (o′o-spo-ran′je-um)

Obsolete term for oogonium (2) . [oospore + G. angeion, vessel]

oospore
oospore (o′o-spor)

A thick-walled fungus spore that develops from a female gamete either through fertilization or parthenogenesis in an oogonium. [see Oospora]

ootheca
ootheca (o-oth-e′ka)

1. An egg case found in some lower animals. 2. Rarely used term for ovary. [G. oon, egg, + theke, box, case]

ootid
ootid (o′o-tid)

The nearly mature ovum after the first meiotic division has been completed and the second initiated; in most higher mammals, the second meiotic division is not completed unless fertilization occurs. [G. ootidion, a diminutive egg. See -id (2)]

ootype
ootype (o′o-tip)

The central portion of the ovarian complex of trematodes and cestodes in which fertilization takes place and the vitellarian or eggshell materials are coated over the egg; this occurs in a rapid, stamping-mill sequence, after which eggs pass into the uterus for tanning of the shell, storage, and passage toward the genital pore. [G. oon, egg, + typos, stamp, print]

OP
OP

Abbreviation for occipitoposterior position.

opacification
opacification (o-pas′i-fi-ka′shun)

1. The process of making opaque. 2. The formation of opacities. [L. opacus, shady]

opacity
opacity (o-pas′i-te)

1. A lack of transparency; an opaque or nontransparent area. 2. On a radiograph, a more transparent area is interpreted as an o. to x-rays in the body. 3. Mental dullness. [L. opacitas, shadiness]
nodular o. a solitary, round, circumscribed shadow found in the lung on chest radiograph; causes include granuloma, primary or metastatic carcinoma, benign tumor, vascular malformation. SYN: coin lesion of lungs.
snowball o. a spherical, white body seen in the vitreous in asteroid hyalosis.

opalescent
opalescent (o-pa-les′ent)

Resembling an opal in the display of various colors; denoting certain bacterial cultures. [Fr. fr. L. opalus, opal]

Opalski
Opalski

Adam, Polish physician, 1897–1963. See O. cell.

opaque
opaque (o-pak′)

Impervious to light; not translucent or only slightly so. Cf.:radiopaque. [Fr. fr. L. opacus, shady]

open
open (o′pen)

1. Not closed; exposed, said of a wound. 2. To enter or expose, as a wound or cavity. [A.S.]

opening
opening (o′pen-ing) [TA]

A gap in or entrance to an organ, tube, or cavity. SEE ALSO: aperture, fossa, ostium, orifice, pore.
access o. SYN: access.
aortic o. SYN: aortic hiatus.
o. of aqueduct of midbrain [TA] entrance to the cerebral aqueduct; point at which the caudal part of the third ventricle is continuous with the cerebral aqueduct of the midbrain; located on the midline immediately ventral to the posterior commissure. SYN: apertura aqueductus mesencephali [TA] , apertura aqueductus cerebri&star, o. of cerebral aqueduct&star, aditus ad aqueductum cerebri, Bartholin anus.
cardiac o. SYN: cardial orifice.
openings of carotid canal [TA] the o. at each extremity of the carotid canal in the pyramidal petrous part of the temporal bone; the external o. of the carotid canal is on the inferior surface of the pyramid; the internal o. of the canal is at the apex of the petrous part. SYN: carotid foramen.
caval o. of diaphragm [TA] an o. in the right lobe of the central tendon of the diaphragm that transmits the inferior vena cava and branches of the right phrenic nerve. SYN: foramen of vena cava, foramen quadratum, foramen venae cavae, vena caval foramen.
o. of cerebral aqueduct o. of aqueduct of midbrain.
o. of coronary sinus [TA] orifice by which the coronary sinus enters and drains into the right atrium of the heart. SYN: ostium sinus coronarii [TA] .
esophageal o. SYN: esophageal hiatus.
external o. SYN: meatus.
o. of external acoustic meatus SYN: external acoustic pore.
external o. of cochlear canaliculus [TA] the external o. of the cochlear aqueduct on the temporal bone medial to the jugular fossa. SYN: apertura canaliculi cochleae, external aperture of cochlear canaliculus.
external o. of urethra SYN: external urethral orifice.
femoral o. SYN: adductor hiatus.
o. of frontal sinus [TA] one of a pair of openings in the floor of the frontal sinuses in the nasal part of the frontal bone, through which the frontal sinuses communicate with the ethmoidal infundibulum via the frontonasal duct. SYN: apertura sinus frontalis [TA] , frontal sinus aperture.
ileocecal o. SYN: ileal orifice.
o. of inferior vena cava [TA] the orifice through which the inferior vena cava opens into the right atrium. SYN: ostium venae cavae inferioris [TA] , orifice of inferior vena cava.
internal acoustic o. [TA] SYN: internal acoustic pore.
o. of internal acoustic meatus SYN: internal acoustic pore.
internal urethral o. internal urethral orifice.
lacrimal o. SYN: lacrimal punctum.
oral o. oral fissure.
orbital o. [TA] the somewhat quadrangular anterior entrance to the orbit that forms the base of the pyramid-shaped orbital cavity. It is bounded by the sharp supra-, infra-, and lateral orbital margins and a less obvious medial margin on each side of the upper nose. SYN: aditus orbitae [TA] , aperture of orbit.
openings of papillary ducts [TA] numerous minute openings, the apertures of the papillary ducts converging on the apical pole of each renal papilla. SYN: foramina papillaria renis [TA] , papillary foramina of kidney.
pharyngeal o. of eustachian tube SYN: pharyngeal o. of pharyngotympanic (auditory) tube.
pharyngeal o. of pharyngotympanic (auditory) tube [TA] an o. in the upper part of the nasopharynx about 1.2 cm behind the posterior extremity of the inferior concha on each side. SYN: ostium pharyngeum tubae auditivae [TA] , ostium pharyngeum tubae auditoriae&star, pharyngeal o. of eustachian tube.
piriform o. SYN: piriform aperture.
o. of pulmonary trunk [TA] the o. of the pulmonary trunk from the right ventricle, guarded by the pulmonary valve. SYN: ostium trunci pulmonalis [TA] , pulmonary orifice.
openings of pulmonary veins [TA] the orifices of the pulmonary veins, usually two on each side, in the wall of the left atrium. SYN: ostia venarum pulmonalium [TA] .
saphenous o. [TA] the o. in the fascia lata inferior to the medial part of the inguinal ligament through which the saphenous vein passes to enter the femoral vein. SYN: hiatus saphenus [TA] , fossa ovalis (2) , saphenous hiatus.
openings of smallest cardiac veins [TA] a number of fossae in the wall of the right atrium, containing the openings of minute intramural veins. SYN: foramina of the smallest veins of heart, foramina of the venae minimae, foramina venarum minimarum cordis, Lannelongue foramina, thebesian foramina, Vieussens foramina.
o. of the sphenoidal sinus [TA] one of the pair of openings in the body of the sphenoid bone through which the sphenoid sinuses communicate with the sphenoethmoidal recess of the nasal cavity. SYN: apertura sinus sphenoidalis [TA] , sphenoidal sinus aperture.
o. of superior vena cava [TA] the point of entry of the superior vena cava into the right atrium. SYN: ostium venae cavae superioris [TA] , orifice of superior vena cava.
tendinous o. SYN: adductor hiatus.
tympanic o. of canaliculus for chorda tympani SYN: tympanic aperture of canaliculus for chorda tympani.
tympanic o. of eustachian tube SYN: tympanic o. of pharyngotympanic (auditory) tube.
tympanic o. of pharyngotympanic (auditory) tube [TA] an o. in the anterior part of the tympanic cavity below the canal for the tensor tympani (muscle). SYN: ostium tympanicum tubae auditivae [TA] , tympanic o. of eustachian tube.
ureteral o. SYN: ureteric orifice.
urethral openings external urethral orifice, internal urethral orifice.
uterine o. of uterine tubes SYN: uterine ostium of uterine tubes.
o. of uterus SYN: external os of uterus.
vaginal o. SYN: vaginal orifice.
vertical o. SYN: vertical dimension.
o. of vestibular canaliculus [TA] the external o. of the vestibular aqueduct on the posterior surface of the petrous part of the temporal bone near the groove for the sigmoid sinus. SYN: apertura canaliculi vestibuli, external aperture of vestibular aqueduct.

operable
operable (op′er-a-bl)

Denoting a patient or condition on which a surgical procedure can be performed with a reasonable expectation of cure or relief.

operant
operant (op′er-ant)

In conditioning, any behavior or specific response chosen by the experimenter; its frequency is intended to increase or decrease by the judicious pairing with it of a reinforcer when it occurs. SYN: target behavior (1) , target response.

operate
operate (op′er-at)

1. To work upon the body by the hands or by means of cutting or other instrument. 2. To perform a surgical procedure. 3. To cause a movement of the bowels; said of a laxative or cathartic remedy. [L. operor, pp. -atus, to work, fr. opus, work]

operation
operation (op-er-a′shun)

1. Any surgical procedure. 2. The act, manner, or process of functioning. SEE ALSO: method, procedure, technique.
Altemeier o. an o. for rectal prolapse that involves a sleeve resection of the prolapsed rectum and colon with a primary anastomosis performed transanally.
Arlt o. transplantation of the eyelashes back from the edge of the lid in trichiasis.
arterial switch o. o. for complete transposition of the great arteries; the most common way to repair this defect consists of switching the aorta and pulmonary arteries and implanting the coronary arteries into the neoaorta (the original pulmonary artery).
Ball o. division of the sensory nerve trunks supplying the anus, for relief of pruritus ani.
Barkan o. goniotomy for congenital glaucoma under direct observation of the anterior chamber angle.
Bassini o. SYN: Bassini herniorrhaphy.
Battista o. SYN: left ventricular volume reduction surgery.
Belsey Mark o. SYN: Belsey fundoplication.
Billroth o. I excision of the pylorus and antrum and partial closure of the gastric end with end-to-end anastomosis of stomach and duodenum.
Billroth o. II excision of the pylorus and antrum with closure of the cut ends of the duodenum and stomach, followed by a gastrojejunostomy.
Blalock-Hanlon o. the creation of a large atrial septal defect as a palliative procedure for complete transposition of the great arteries.
Blalock-Taussig o. an o. for congenital malformations of the heart, in which an abnormally small volume of blood passes through the pulmonary circuit; blood from the systemic circulation is directed to the lungs by anastomosing the right or left subclavian artery to the right or left pulmonary artery.
bloodless o. an o. performed with negligible loss of blood.
Bozeman o. an o. for uterovaginal fistula, the cervix uteri being attached to the bladder and opening into its cavity.
Bricker o. an o. utilizing an isolated segment of ileum to collect urine from the ureters and conduct it to the skin surface.
Brock o. transventricular valvotomy for relief of pulmonic valvar stenosis. Obsolete procedure.
Brunschwig o. SYN: total pelvic exenteration.
Caldwell-Luc o. an intraoral procedure for opening into the maxillary antrum through the supradental (canine) fossa above the maxillary premolar teeth. SYN: intraoral antrostomy, Luc o..
Carmody-Batson o. reduction of fractures of the zygoma and zygomatic arch through an intraoral incision above the maxillary molar teeth.
cesarean o. cesarean section, cesarean hysterectomy.
commando o. SYN: commando procedure.
concrete operations in the psychology of Piaget, a stage of development in thinking, occurring approximately between 7 and 11 years of age, during which a child becomes capable of reasoning about concrete situations.
Cotte o. SYN: presacral neurectomy.
cricoid split o. an o. to repair subglottic stenosis by transecting the anterior and posterior aspects of the ring of the cricoid cartilage, with or without the insertion of grafts to reconstruct the subglottic lumen.
Dana o. SYN: posterior rhizotomy.
Dandy o. third ventriculostomy, trigeminal rhizotomy.
Daviel o. extracapsular cataract extraction.
debulking o. excision of a major part of a malignant tumor that cannot be completely removed.
decompression operations decompression.
Doyle o. paracervical uterine denervation.
Elliot o. trephining of the eyeball at the corneoscleral margin to relieve tension in glaucoma.
Emmet o. SYN: trachelorrhaphy.
endolymphatic shunt o. an o. to establish a communication between the endolymphatic sac and the cerebrospinal fluid space for the treatment of Ménière disease.
Estes o. an o. for sterility in which a portion of an ovary is implanted on one uterine cornu.
fenestration o. a rarely used surgical procedure producing an opening from the external auditory canal to the membranous labyrinth to improve hearing in hearing impairment of the conduction type due to otosclerosis.
filtering o. a surgical procedure for creation of a fistula between the anterior chamber of the eye and the subconjunctival space in treatment of glaucoma.
Finney o. gastroduodenostomy that creates, by the technique of closure, a large opening to ensure free emptying from the stomach.
flap o. 1. SYN: flap amputation. 2. in dental surgery, an o. in which a portion of the mucoperiosteal tissues is surgically detached from the underlying bone or impacted tooth for better access and visibility in exploring the area covered by the tissue. SEE ALSO: flap.
Fontan o. SYN: Fontan procedure.
formal operations in the psychology of Piaget, a stage of development in thinking, occurring approximately between 11 and 15 years of age, during which a child becomes capable of reasoning about abstract situations; reasoning at this stage is comparable to that of normal adults but less sophisticated.
Fothergill o. SYN: Manchester o..
Frazier-Spiller o. trigeminal rhizotomy.
Fredet-Ramstedt o. SYN: pyloromyotomy.
Freund o. 1. total abdominal hysterectomy for uterine cancer; 2. chondrotomy to relieve Freund anomaly.
Gilliam o. an o. for retroversion of the uterus by suturing round ligaments to abdominal wall fascia.
Gillies o. a technique for reducing fractures of the zygoma and the zygomatic arch through an incision in the temporal region above the hairline.
Gil-Vernet o. SYN: extended pyelotomy.
Glenn o. anastomosis between the superior vena cava and the right main pulmonary artery to increase pulmonary blood flow as a palliative correction for tricuspid atresia.
Graefe o. 1. removal of cataract by a limbal incision with capsulotomy and iridectomy. Both operations were landmarks in the field of ophthalmic surgery; 2. iridectomy for glaucoma.
Gritti o. SYN: Gritti-Stokes amputation.
Halsted o. 1. an o. for the radical correction of inguinal hernia; 2. SYN: radical mastectomy.
Hartmann o. resection of the sigmoid colon beginning at or just above the peritoneal reflexion and extending proximally, with closure of the rectal stump and end-colostomy.
Heaney o. technique for vaginal hysterectomy.
Heller o. esophagomyotomy just above the gastroesophageal junction.
Hill o. repair of hiatus hernia; anchoring the esophagogastric junction within the abdomen by attaching it to the medial arcuate ligament.
Hoffa o. in congenital dislocation of the hip, a rarely used o. consisting of hollowing out the acetabulum and reduction of the head of the femur after severing the muscles inserted into the upper portion of the bone.
Hofmeister o. partial gastrectomy with closure of a portion of the lesser curvature and retrocolic anastomosis of the remainder to jejunum.
Hummelsheim o. transplantation of a normal ocular rectus muscle, to substitute for a paralyzed muscle.
Hunter o. ligation of an artery proximal and distal to an aneurysm.
interval o. an o. performed during a period of quiescence or of intermission in the condition necessitating surgery.
Jacobaeus o. obsolete term for pleurolysis.
Jansen o. an o. for frontal sinus disease; the lower wall and lower portion of the anterior wall are removed and the mucous membrane is curetted away.
Kasai o. SYN: portoenterostomy.
Kazanjian o. surgical extension of the vestibular sulcus of edentulous ridges to increase their height and to improve denture retention. SEE ALSO: ridge extension.
Keen o. removal of sections of the posterior branches of the spinal nerves to the affected muscles, and of the spinal accessory nerve, as a cure for torticollis.
Keller-Madlener o. an o. for treatment of gastric ulcer located in the proximal cardia that involves 75% gastrectomy and gastrojejunostomy.
Kelly o. 1. correction of retroversion of the uterus by plication of uterosacral ligaments; 2. correction of urinary stress incontinence by vaginally placing sutures beneath the bladder neck.
Killian o. an o. for frontal sinus disease in which the entire anterior wall is removed and the mucous membrane is curetted away; the ethmoid cells are removed through an opening in the nasal process of the maxillary bone, and the upper portion of the medial wall of the orbit is removed as well.
Koerte-Ballance o. operative anastomosis of the facial and hypoglossal nerves for the treatment of facial paralysis.
Kondoleon o. excision of strips of subcutaneous connective tissue for the relief of elephantiasis.
Kraske o. removal of the coccyx and excision of the left wing of the sacrum to afford approach for resection of the rectum for cancer or stenosis.
Krönlein o. orbital decompression through the anterior lateral wall of the orbit.
Ladd o. division of Ladd band to relieve duodenal obstruction in malrotation of the intestine.
Lambrinudi o. a form of triple arthrodesis done in such a manner as to prevent foot-drop such as occurs in poliomyelitis.
Laroyenne o. puncture of Douglas pouch to evacuate the pus and to secure drainage in cases of pelvic suppuration.
Lash o. removal of a wedge of the internal cervical os with suturing of the internal os into a tighter canal structure.
LeCompte o. SYN: LeCompte maneuver.
Leriche o. SYN: periarterial sympathectomy.
Lisfranc o. SYN: Lisfranc amputation.
Longmire o. intrahepatic cholangiojejunostomy with partial hepatectomy for biliary obstruction.
Luc o. SYN: Caldwell-Luc o..
Madlener o. tubal sterilization by clamp and tie.
major o. an extensive, relatively difficult surgical procedure involving vital organs and/or in itself hazardous to life.
Manchester o. a vaginal o. for prolapse of the uterus, consisting of cervical amputation and parametrial fixation (cardinal ligaments) anterior to the uterus. SYN: Fothergill o.. [Manchester, England]
Mann-Williamson o. an o. performed on experimental animals (dogs) in research on peptic ulcer, the duodenum with its alkaline secretions being transplanted into the ileum and the cut end of the jejunum anastomosed to the pylorus; the animals develop ulcers in the jejunum, which directly receives the gastric juice.
Marshall-Marchetti-Krantz o. an o. for urinary stress incontinence, performed retropubically.
Mayo o. an o. for the radical cure of umbilical hernia; the neck of the sac is exposed by two elliptical incisions, the gut is returned to the abdomen, the sac and adherent omentum are cut away, and the fascial edges of the opening are overlapped with mattress sutures.
McIndoe o. o. for the development of a neovagina using a split thickness skin graft over a vaginal mold.
McVay o. repair of inguinal and femoral hernias by suture of the transversus abdominis muscle and its associated fasciae (transversus layer) to the pectineal ligament.
mika o. the establishment of a permanent fistula in the bulbous portions of the urethra to render the man incapable of procreating; said to be a practice among certain Australian aborigines. [Australian native term]
Mikulicz o. excision of bowel in two stages: 1) exteriorizing the diseased area, suturing efferent and afferent limbs together, and closing the abdomen around them, after which the diseased part is excised; 2) at a later time, cutting the spur with an enterotome and closing the stoma extraperitoneally.
Miles o. combined abdominoperineal resection for carcinoma of the rectum.
minor o. a surgical procedure of relatively slight extent and not in itself hazardous to life.
morcellation o. vaginal hysterectomy in which the uterus is removed in multiple pieces after being split or partitioned.
Motais o. transplantation of the middle third of the tendon of the superior rectus muscle of the eyeball into the upper lid, between the tarsus and skin, to supplement the action of the levator muscle in ptosis.
Mules o. evisceration of the eyeball followed by the insertion within the sclera of a spherical prosthesis to support an artificial eye.
Mustard o. correction, at the atrial level, of hemodynamic abnormality caused by transposition of the great arteries by an intraatrial baffle to direct pulmonary venous blood through the tricuspid orifice into the right ventricle and the systemic venous blood through the mitral valve into the left ventricle. SYN: Mustard procedure.
Naffziger o. orbital decompression for severe malignant exophthalmos by removal of the lateral and superior orbital walls.
Nissen o. SYN: Nissen fundoplication.
Norton o. extraperitoneal cesarean section by a paravesical approach.
Norwood o. o. performed in infants with subaortic stenosis and tricuspid atresia; the pulmonary artery is divided and both ends are attached to the aorta, the distal end via a prosthetic graft.
Ogston-Luc o. an o. for frontal sinus disease; a skin incision is made from the inner third of the edge of the orbit toward the root of the nose or outward; the periosteum is pushed upward and outward, and the sinus is opened on the outer side of the median line; then a wide opening is made by curetting the nasofrontal duct, interior of the sinus, and anterior ethmoid cells.
Ogura o. orbital decompression by removal of the floor of the orbit through an opening made in the supradental (canine) fossa.
Ombrédanne o. a technique whereby the mobilized testis is brought down into the scrotum and through the scrotal septum, to be affixed to the tissues in the contralateral scrotal pouch. SYN: transseptal orchiopexy.
Payne o. a jejunoileal bypass for morbid obesity utilizing end-to-side anastomosis of the upper jejunum to the terminal ileum, with closure of the proximal end of the bypassed intestine.
Pólya o. SYN: Pólya gastrectomy.
Pomeroy o. excision of a ligated portion of the fallopian tubes.
Potts o. direct side-to-side anastomosis between aorta and pulmonary artery as a palliative procedure in congenital malformation of the heart. SYN: Potts anastomosis.
pubovaginal o. operative procedure for urinary incontinence. A strip of tissue, usually autologous rectus abdominis fascia, is used to suspend or elevate bladder neck and posterior urethra toward pubic symphysis.
Putti-Platt o. a procedure for recurrent anterior dislocation of shoulder joint. SYN: Putti-Platt procedure.
radical o. for hernia an o. by which the hernia is not only reduced, but the hernial defect is also repaired.
Ramstedt o. SYN: pyloromyotomy.
Rastelli o. for “anatomic” repair of transposition of the great arteries (ventriculoarterial discordance) with ventricular septal defect and left ventricular outflow tract obstruction; conduits are used to create left ventricular to aortic continuity and right ventricular to pulmonary artery continuity. All septal defects are obliterated, as are any previously constructed palliative shunts.
Récamier o. curettage of the uterus.
Ridell o. removal of the entire anterior and inferior walls of the frontal sinus, for chronic inflammation of that cavity.
Ripstein o. an o. for rectal prolapse that involves a transabdominal approach with dissection around the rectum and placement of a mesh sling to prevent the bowel from prolapsing through the anus.
Roux-en-Y o. anastomosis of the distal end of the divided upper jejunum to the stomach, esophagus, biliary tract, or other structure and anastomosis of the proximal end to the side of the jejunum a little further distal.
Saenger o. cesarean section followed by careful closure of the uterine wound by three tiers of sutures.
Schauta vaginal o. an extensive extirpation of the uterus and the adnexa, using the vaginal approach facilitated by Schuchardt o..
Schroeder o. excision of diseased endocervical mucosa.
Schuchardt o. a paravaginal rectal displacement incision, a surgical technique of making the upper vagina accessible for fistula closure or radical surgery via the vagina.
scleral buckling o. an o. performed in retinal detachment to indent the sclerochoroidal wall.
Scott o. a jejunoileal bypass for morbid obesity utilizing end-to-end anastomosis of the upper jejunum to the terminal ileum, with the bypassed intestine closed proximally and anastomosed distally to the colon.
second-look o. exploratory celiotomy within a year after apparently curative resection of intraabdominal cancer, in patients with no sign or symptom of recurrence, to resect an occult tumor if present.
Senning o. an atrial switch o. for patients with transposition of the great arteries that employs a septal flap instead of excising the atrial septum as in the Mustard o., thus minimizing foreign material and allowing for growth.
seton o. an o. for advanced glaucoma; passage of a tube or seton into the anterior chamber to act as a wick.
Shirodkar o. a cerclage procedure done by purse-string suturing of an incompetent cervical os with a nonabsorbent suture material.
Sistrunk o. excision of the thyroglossal cyst and duct including the midportion of the hyoid bone through, or near, which the duct traverses.
Smith o. SYN: Smith-Indian o..
Smith-Boyce o. SYN: anatrophic nephrotomy.
Smith-Indian o. a surgical technique for removal of cataract within the capsule. SYN: Smith o..
Soave o. endorectal pull-through for treatment of congenital megacolon.
Spinelli o. an o. splitting the anterior wall of the prolapsed uterus and reversing the organ preliminary to reduction.
stapes mobilization o. now infrequently used o. involving fracture of otosclerotic tissue immobilizing the stapes to restore hearing.
Stoffel o. division of certain motor nerves for the relief of spastic paralysis.
Stookey-Scarff o. third ventriculostomy.
Sturmdorf o. conical removal of the endocervix.
subcutaneous o. an o., as for the division of a tendon, performed without incising the skin other than by a minute opening made by the entering knife.
Syme o. SYN: Syme amputation.
talc o. an obsolete o. in which magnesium silicate (talc) powder is applied to the epicardium to create a sterile granulomatous pericarditis and thus promote pericardial anastomoses with the coronary circulation. SYN: poudrage (2) .
TeLinde o. SYN: modified radical hysterectomy.
Torek o. a two-stage o. for bringing down an undescended testicle.
Trendelenburg o. a pulmonary embolectomy.
Urban o. extended radical mastectomy, including en bloc resection of internal mammary lymph nodes, part of the sternum, and costal cartilages.
Waters o. an extraperitoneal cesarean section with a supravesical approach.
Waterston o. a surgically created anastomosis between the pulmonary artery and the ascending aorta to palliate adult tetralogy of Fallot.
Wertheim o. a radical o. for carcinoma of the uterus in which as much as possible of the vagina is excised and there is wide lymph node excision.
Whipple o. SYN: pancreatoduodenectomy.
Whitehead o. excision of hemorrhoids by two circular incisions above and below involved veins, allowing normal mucosa to be pulled down and sutured to anal skin.

operative
operative (op′er-a-tiv)

1. Relating to, or effected by means of an operation. 2. Active or effective.

operator
operator (op′er-a-tor)

1. One who performs an operation or operates equipment. 2. In genetics, a sequence of DNA that interacts with a repressor of operon to control the expression of adjacent structural genes. See o. gene. 3. A symbol representing a mathematical operation. [L. worker, fr operor, to work]

opercular
opercular (o-per′ku-lar)

Relating to an operculum.

operculated
operculated (o-per′ku-la-ted)

Provided with a lid (operculum); denoting members of the mollusk class Gastropoda (the snails), subclass Prosobranchiata (operculate snails), and the eggs of certain parasitic worms such as the digenetic trematodes (except the schistosomes) and the broad fish tapeworm, Diphyllobothrium latum.

operculitis
operculitis (o-perk-u-li′tis)

Originating under an operculum. [operculum + G. -itis, inflammation]

operculum
operculum, gen. operculi, pl .opercula (o-per′ku-lum, -li, -la)

1. Anything resembling a lid or cover. 2. [TA] In anatomy, the portions of the frontal (o. frontale [TA], frontal o. [TA]), parietal (o. parietale [TA], parietal o. [TA]), and temporal (o. temporale [TA], temporal o. [TA]) lobes bordering the lateral sulcus and covering the insula. 3. In parasitology, the lid or caplike cover of the shell opening of operculated freshwater snails in the subclass Prosobranchiata, and of the eggs of certain trematode and cestode parasites. 4. The attached flap in the tear of retinal detachment. 5. The mucosal flap partially or completely covering an unerupted tooth. [L. cover or lid, fr. operio, pp. opertus, to cover]
o. ilei SYN: ileal sphincter.
occipital o. a portion of the occipital lobe of the brain demarcated by the simian fissure (sulcus lunatus) when present in humans.
trophoblastic o. the mushroom-shaped plug of fibrin that fills the aperture in the endometrium made by the implanting ovum.

operon
operon (op′er-on)

A genetic functional unit that controls production of a messenger RNA; it consists of an operator gene and two or more structural genes located in sequence in the cis position on one chromosome. [L. operor, to work, act, + -on]
Lac o. a collection of adjacent bacterial genes responsible for the entry and metabolism of lactose; contains the genes coding for three enzymes and is flanked by a repressor and a promoter region to control expression.

ophiasis
ophiasis (o-fi′a-sis)

A form of alopecia areata in which the loss of hair occurs in bands along the scalp margin partially or completely encircling the head. [G., fr. ophis, snake]

Ophidia
Ophidia (o-fid′e-a)

The snakes, a suborder of the class Reptilia, including the families Colubridae, Crotalidae, Elapidae, Hydrophyidae, and Viperidae. [G. ophidion, dim. of ophis, a serpent]

ophidiasis
ophidiasis (o′fi-di′a-sis)

Poisoning by a snake. SYN: ophidism. [G. ophidion, dim. of ophis, a serpent]

ophidiophobia
ophidiophobia (o-fid′e-o-fo′be-a)

Morbid fear of snakes. [G. ophidion, a small snake, + phobos, fear]

ophidism
ophidism (o′fid-izm)

SYN: ophidiasis.

ophritis
ophritis (of-ri′tis)

Dermatitis in the region of the eyebrows. SYN: ophryitis. [G. ophrys, eyebrow, + -itis, inflammation]

ophryitis
ophryitis (of-re-i′tis)

SYN: ophritis.

ophryogenes
ophryogenes (of′re-yo-jen-′enz)

Related to the eyebrows. [Mod. L., fr. G. ophrys, eyebrow, + suffix -genes, arising from]

ophryon
ophryon (of′re-on)

The point on the midline of the forehead just above the glabella (1). SYN: supranasal point, supraorbital point. [G. ophrys, eyebrow]

Ophryoscolecidae
Ophryoscolecidae (of′re-o-sko-les′i-de)

A family of ciliate protozoa occurring in the rumen and reticulum of ruminant animals, characterized by having cilia arranged in spiral membranelles around the mouth (adoral) and in some genera also in a dorsal (metoral) position. The most important genera are Entodinium, Diplodinium, Epidinium, and Ophryoscolex, which are thought to contribute to ruminant nutrition by converting cellulose in plant material ingested by the ruminant into readily digestible animal protein of their own bodies. [G. ophrys, eyebrow, + skolex, a worm]

ophryosis
ophryosis (of-re-o′sis)

Spasmodic twitching of the upper portion of the orbicularis palpebrarum muscle causing a wrinkling of the eyebrow. [G. ophrys, eyebrow, + -osis, condition]

ophthalm- ophthalm-

See ophthalmo-.

ophthalmalgia
ophthalmalgia (of′thal-mal′je-a)

SYN: oculodynia. [ophthalmo- + G. algos, pain]

ophthalmia
ophthalmia (of-thal′me-a)

1. Severe, often purulent, conjunctivitis. 2. Inflammation of the deeper structures of the eye. [G.]
catarrhal o. a mild form of conjunctivitis with mucopurulent secretion.
caterpillar-hair o. SYN: o. nodosa.
Egyptian o. SYN: trachoma.
gonorrheal o. acute purulent conjunctivitis excited by Neisseria gonorrhoeae. SYN: blennophthalmia (2) , blennorrhea conjunctivalis, gonorrheal conjunctivitis.
granular o. SYN: trachoma.
metastatic o. 1. sympathetic o; 2. choroiditis in septicemia.
o. neonatorum a conjunctival inflammation occurring within the first 10 days of life; causes include Neisseria gonorrhoeae, Staphylococcus, Streptococcus pneumoniae, and Chlamydia trachomatis. SYN: blennorrhea neonatorum, infantile purulent conjunctivitis, neonatal conjunctivitis.
o. nivalis SYN: ultraviolet keratoconjunctivitis.
o. nodosa the presence of nodular swellings on the conjunctiva, caused by penetration of ocular tissues by the hairs of caterpillars. SYN: caterpillar-hair o..
phlyctenular o. SYN: phlyctenular conjunctivitis.
purulent o. purulent conjunctivitis, usually of gonorrheal origin.
spring o. SYN: vernal conjunctivitis.
sympathetic o. a serous or plastic uveitis caused by a perforating wound of the uvea followed by a similar severe reaction in the other eye that may lead to bilateral blindness. SYN: transferred o..
transferred o. SYN: sympathetic o..

ophthalmic
ophthalmic (of-thal′mik)

Relating to the eye. SYN: ocular (1) . [G. ophthalmikos]

ophthalmic acid
ophthalmic acid

A tripeptide occurring in lens, similar to glutathione but differing in the replacement of cysteine by α-amino-n-butyric acid ( i.e., in the replacement of –SH by –CH₃); a potent inhibitor of glyoxalase. Cf.:norophthalmic acid.

ophthalmo- ophthalmo-, ophthalm-

Relationship to the eye. SEE ALSO: oculo-. [G. ophthalmos]

ophthalmodynamometer
ophthalmodynamometer (of-thal′mo-di-na-mom′e-ter)

An instrument to measure the blood pressure in the retinal vessels. [ophthalmo- + G. dynamis, power, + metron, measure]
Bailliart o. an instrument used to measure the blood pressure of the central retinal artery; of value in diagnosing occlusion of the proximal carotid artery.
suction o. an o. with a suction disk that increases ocular pressure during ophthalmoscopic observation of the retinal artery.

ophthalmodynamometry
ophthalmodynamometry (of-thal′mo-di-na-mom′e-tre)

The measurement of blood pressure in the retinal vessels by means of an ophthalmodynamometer. [ophthalmo- + G. dynamis, power, + metron, measure]

ophthalmolith
ophthalmolith (of-thal′mo-lith)

SYN: dacryolith. [ophthalmo- + G. lithos, stone]

ophthalmologist
ophthalmologist (of-thal-mol′o-jist)

A specialist in ophthalmology. SYN: oculist.

ophthalmology
ophthalmology (of-thal-mol′o-je)

The medical specialty concerned with the eye, its diseases, and refractive errors. [ophthalmo- + G. logos, study]

ophthalmomalacia
ophthalmomalacia (of-thal′mo-ma-la′she-a)

Abnormal softening of the eyeball. [ophthalmo- + G. malakia, softness]

ophthalmomelanosis
ophthalmomelanosis (of-thal′mo-mel-a-no′sis)

Melanotic discoloration of the conjunctiva and adjoining tissues.

ophthalmometer
ophthalmometer (of-thal-mom′e-ter)

SYN: keratometer. [ophthalmo- + G. metron, measure]

ophthalmomycosis
ophthalmomycosis (of-thal′mo-mi-ko′sis)

Any disease of the eye or its appendages caused by a fungus. [ophthalmo- + G. mykes, fungus, + -osis, condition]

ophthalmomyiasis
ophthalmomyiasis (of-thal′mo-mi-i′a-sis)

SYN: ocular myiasis.

ophthalmopathy
ophthalmopathy (of-thal-mop′a-the)

Any disease of the eyes. SYN: oculopathy. [ophthalmo- + G. pathos, suffering]
endocrine o. SYN: Graves o..
external o. any disease of the conjunctiva, cornea, or adnexa of the eye.
Graves o. exophthalmos caused by increased water content of retroocular orbital tissues; associated with thyroid disease, usually hyperthyroidism. SYN: endocrine o., Graves orbitopathy.
internal o. any disease of the internal structures of the eyeball.

ophthalmoplegia
ophthalmoplegia (of-thal-mo-ple′je-a)

Paralysis of one or more of the ocular muscles. [ophthalmo- + G. plege, stroke]
chronic progressive external o. (CPEO) a specific type of slowly worsening weakness of the ocular muscles, usually associated with a pigmentary retinopathy. See Kearns-Sayre syndrome, oculopharyngeal dystrophy. SYN: ocular myopathy.
exophthalmic o. o. with protrusion of the eyeballs due to increased water content of orbital tissues incidental to thyroid disorders, usually hyperthyroidism.
o. externa paralysis affecting one or more of the extrinsic eye muscles. SYN: external o..
external o. SYN: o. externa.
fascicular o. o. due to a lesion within the brainstem.
fibrotic o. [MIM*135700] o. that may be congenital in association with blepharoptosis; an autosomal dominant disorder.
o. interna paralysis affecting only the sphincter muscle of the pupil and the ciliary muscle. SYN: internal o..
internal o. SYN: o. interna.
internuclear o. (INO) o. in lesions of the medial longitudinal fasciculus, with failure of adduction in horizontal gaze but with retention of convergence.
nuclear o. o. due to a lesion of the nuclei of origin of the motor nerves of the eye.
orbital o. o. due to a lesion within the orbit.
Parinaud o. SYN: Parinaud syndrome.
o. partialis incomplete o. involving only one or two of the extrinsic or intrinsic ocular muscles.
o. progressiva progressive upper bulbar palsy, due to degeneration of the nuclei of the motor nerves of the eye.
o. totalis paralysis of both the extrinsic and intrinsic ocular muscles.
wall-eyed bilateral internuclear o. (WEBINO) a form of internuclear o. associated with an exotropia.

ophthalmoplegic
ophthalmoplegic (of-thal-mo-ple′jik)

Relating to or marked by ophthalmoplegia.

ophthalmoscope
ophthalmoscope (of-thal′mo-skop)

A device for studying the interior of the eyeball through the pupil. SYN: funduscope. [ophthalmo- + G. skopeo, to examine]
binocular o. an o. that provides a stereoscopic view of the fundus.
demonstration o. an o. by which the fundus may be seen simultaneously by more than one observer.
direct o. an instrument designed to visualize the interior of the eye, with the instrument relatively close to the subject's eye and the observer viewing an upright magnified image.
indirect o. an instrument designed to visualize the interior of the eye, with the instrument at arm's length from the subject's eye and the observer viewing an inverted image through a convex lens located between the instrument and the subject's eye.

ophthalmoscopic
ophthalmoscopic (of′thal-mo-skop′ik)

Relating to examination of the interior of the eye.

ophthalmoscopy
ophthalmoscopy (of-thal-mos′ko-pe)

Examination of the fundus of the eye by means of the ophthalmoscope. SYN: funduscopy.
direct o. o. performed with a direct ophthalmoscope.
indirect o. o. performed with an indirect ophthalmoscope.
o. with reflected light examination of that part of the fundus adjacent to an area illuminated by a sharply focused light.

ophthalmotrope
ophthalmotrope (of-thal′mo-trop)

A model of the two eyes, to each of which are attached weighted cords pulling in the direction of the six extrinsic eye muscles; used to demonstrate the action of the ocular muscles singly or in various combinations. [ophthalmo- + G. tropos, a turning]

ophthalmovascular
ophthalmovascular (of-thal′mo-vas′ku-lar)

Relating to the blood vessels of the eye.

-opia -opia

Vision. [G. ops, eye]

opianine
opianine (o-pi′a-nen)

SYN: noscapine.

opianyl
opianyl (o′pi-a-nil)

SYN: meconin.

opiate
opiate (o′pe-at)

Any preparation or derivative of opium.

opine
opine (o′pen)

A derivative of basic amino acids, produced by crown-gall tumors in plants.

opiocortin
opiocortin (o′pe-o-kor′tin)

SYN: opiomelanocortin.

opioid
opioid (o′pe-oyd)

Originally, a term denoting synthetic narcotics resembling opiates but increasingly used to refer to both opiates and synthetic narcotics.

opiomelanocortin
opiomelanocortin (o′pe-o-mel′a-no-kor′tin)

A linear polypeptide of the pituitary gland that contains in its sequence the sequences of endorphins, MSH, ACTH, and the like, which are split off enzymically; the nucleotide sequence coding has been determined for several species. SYN: opiocortin.

opipramol hydrochloride
opipramol hydrochloride (o-pip′ra-mol)

4-[3-(5H-Dibenz[b.f ]azepin-5-yl)propyl]-1-piperazineethanol dihydrochloride; an antidepressant agent.

opisthenar
opisthenar (o-pis′the-nar)

Dorsum of the hand. [G. back of the hand, from opisthen, behind, + thenar, palm of the hand]

opisthiobasial
opisthiobasial (o-pis′the-o-ba′se-al)

Relating to both opisthion and basion; denoting a line connecting the two or the distance between them.

opisthion
opisthion (o-pis′the-on)

The middle point on the posterior margin of the foramen magnum, opposite the basion. [G. opisthios, posterior]

opisthionasial
opisthionasial (o-pis′the-o-na′ze-al)

Relating to the opisthion and the nasion; denoting the distance between the two points.

opistho- opistho-

Backward, behind, dorsal. [G. opisthen, at the rear, behind]

opisthocheilia
opisthocheilia, opisthochilia (op′is-tho-ki′le-a)

Recession of the lips. [opistho- + G. cheilos, lip]

opisthomastigote
opisthomastigote (o-pis-tho-mas′ti-got)

Term now used instead of herpetomonad for the stage of development of certain insect- and plant-parasitizing flagellates to avoid confusion between the stage and the genus Herpetomonas. In this stage the flagellum arises from the kinetoplast located behind the nucleus and emerges from the anterior end of the organism; an undulating membrane is absent. [opistho- + G. mastix, whip]

opisthorchiasis
opisthorchiasis (op′is-thor-ki′a-sis)

Infection with the Asiatic liver fluke, Opisthorchis viverrini, or other opisthorchids.

opisthorchid
opisthorchid (op-is-thor′kid)

Common name for members of the family Opisthorchiidae.

Opisthorchiidae
Opisthorchiidae (op′is-thor-ke′i-de)

A family of trematodes that includes the genera Opisthorchis and Clonorchis.

Opisthorchis
Opisthorchis (op-is-thor′kis)

Genus of digenetic trematodes (family Opisthorchiidae) found in the bile ducts or gallbladder of fish-eating mammals, birds, and fish. [opistho- + G. orchis, testis]
O. felineus the cat liver fluke, a species frequently found as a human parasite in Eastern Europe, Siberia, India, Japan, and Southeast Asia; adults are lancet-shaped, thin, relatively transparent, and hermaphroditic, with sizes ranging from 7–12 by 2–3 mm; ingested eggs hatch in Bithynia snails, and cercariae encyst on various species of freshwater fish; humans acquire the infection by ingesting raw or inadequately cooked fish; the parasites sometimes cause no evidence of disease, but cholangitis, biliary cirrhosis, and chronic pancreatitis may occur.
O. sinensis SYN: Clonorchis sinensis.
O. viverrini a species of fluke closely related to O. felineus, very common in humans in Thailand; causes opisthorchiasis.

opisthotic
opisthotic (op-is-tho′tik)

Behind the ear. [opistho- + G. ous (ot-), ear]

opisthotonic
opisthotonic (op-is-thot′o-nik, o-pis′tho-ton′ik)

Relating to or characterized by opisthotonos.

opisthotonoid
opisthotonoid (op-is-thot′o-noyd)

Resembling opisthotonos.

opisthotonos
opisthotonos, opisthotonus (op-is-thot′o-nus)

A tetanic spasm in which the spine and extremities are bent with convexity forward, the body resting on the head and the heels. [opistho- + G. tonos, tension, stretching]

Opitz
Opitz

John M., U.S. pediatrician, *1935. See Smith-Lemli-O. syndrome, O. BBB syndrome, O. G syndrome.

opium
opium (o′pe-um)

The air-dried milky exudation obtained by incising the unripe capsules of Papaver somniferum (family Papveraceae) or its variety, P. album. Contains some 20 alkaloids, including morphine, 9–14%; noscapine, 4–8%; codeine, 0.8–2.5%; papaverine, 0.5–2.5%; and thebaine, 0.5–2%. Used as an analgesic, hypnotic, and diaphoretic, and in diarrhea and spasmodic conditions. SYN: gum o., meconium (2) . [L. fr. G. opion, poppy-juice]
Boston o. o. so diluted after importation as barely to meet the official requirements. SYN: pudding o..
deodorized o., denarcotized o. powdered o. treated with purified petroleum benzine that removes certain nauseating and odorous constituents.
granulated o. o. dried and reduced to a coarse powder; it contains 10–10.5% anhydrous morphine.
powdered o. dried and finely powdered o. containing 10% morphine.
pudding o. SYN: Boston o..

opo- opo-

1. The face; an eye. SEE ALSO: facio-. 2. Juice, balm. [G. ops]

opobalsamum
opobalsamum (op-o-bal′sa-mum)

SYN: balm of Gilead. [G. opobalsamon, the juice of the balsam tree, fr. opos, juice, + balsamon]

opodidymus
opodidymus (op-o-did′i-mus)

Conjoined twins with a single body having two heads fused at the back with partially separated facial regions. See conjoined twins, under twin. [G. ops, eye, face, + didymos, twin]

Oppenheim
Oppenheim

Hermann, Berlin neurologist, 1858–1919. See O. disease, O. reflex, O. syndrome, Ziehen-O. disease.

oppilative
oppilative (op-i-la′tiv)

Obstructive to any secretion.

opponens
opponens (o-po′nens)

A name given to several muscles of the fingers or toes, by the action of which these digits are opposed to the others. The o. muscles of the hands act at the carpometacarpal joints, cupping the palm; this enables flexion at the metacarpophalangeal joints to oppose the thumb to the small finger or vice versa. Although comparable muscles in the foot are called “o.,” no opposition occurs in the foot. [L. op-pono (obp-), pres. p. -ens, to place against, oppose]

opportunistic
opportunistic (op′or-too-nis′tik)

1. Denoting an organism capable of causing disease only in a host whose resistance is lowered, e.g., by other diseases or by drugs. 2. Denoting a disease caused by such an organism.

opposure
opposure (op′po-shur)

Bringing together of tissue during suturing.

opsin
opsin

The protein portion of the rhodopsin molecule; at least three separate opsins are located in cone cells.

opsinogen
opsinogen (op-sin′o-jen)

A substance that stimulates the formation of opsonin, such as the antigen contained in a suspension of bacteria used for immunization. SYN: opsogen. [opsonin + -gen]

opsiuria
opsiuria (op-se-oo′re-a)

A more rapid excretion of urine during fasting than after a full meal. [G. opsi, late, + ouron, urine]

opsoclonus
opsoclonus (op′so-klo′nus)

Rapid, irregular, nonrhythmic movements of the eye in horizontal and vertical directions. [G. ops, opos, eye, + klonos, confused motion]

opsogen
opsogen (op′so-jen)

SYN: opsinogen.

opsomania
opsomania (op′so-ma′ne-a)

A rarely used term for a longing for a particular article of diet, or for highly seasoned food. [G. opson, seasoning, + mania, frenzy]

opsonic
opsonic (op-son′ik)

Relating to opsonins or to their utilization.

opsonin
opsonin (op′so-nin)

Any blood serum protein that binds to antigens, enhancing phagocytosis ( e.g., C3b of the complement system, specific antibodies). [G. opson, boiled meat, provisions, fr. hepso, to boil, + -in]
common o. SYN: normal o..
immune o. SYN: specific o..
normal o. o. normally present in the blood, i.e., without stimulation by a known, specific antigen such as certain complement components; it is relatively thermolabile and reacts with various organisms. SYN: common o., thermolabile o..
specific o. antibodies formed in response to stimulation by a specific antigen, either as a result of an attack of a disease or as a result of injections with a suitably prepared suspension of the specific microorganism. SYN: immune o., thermostable o..
thermolabile o. SYN: normal o..
thermostable o. SYN: specific o..

opsonization
opsonization (op′so-ni-za′shun)

The process by which bacteria and other cells are altered in such a manner that they are more readily and more efficiently engulfed by phagocytes.

opsonocytophagic
opsonocytophagic (op′so-no-si′to-fa′jik)

Pertaining to the increased efficiency of phagocytic activity of the leukocytes in blood that contains specific opsonin. [opsonin + G. kytos, a hollow (cell), + phago, to eat]

opsonometry
opsonometry (op-so-nom′e-tre)

Determination of the opsonic index or the opsonocytophagic activity.

opsonophilia
opsonophilia (op-so-no-fil′e-a)

The condition in which bacteria readily unite with opsonins, thereby sensitizing them for more effective phagocytosis. [opsonin + G. phileo, to love]

opsonophilic
opsonophilic (op-so-no-fil′ik)

Pertaining to, characterized by, or resulting in opsonophilia.

optic
optic, optical (op′tik, op′ti-kal)

Relating to the eye, vision, or optics. [G. optikos]

optician
optician (op-tish′an)

One who practices opticianry.

opticianry
opticianry (op-tish′an-re)

The professional practice of filling prescriptions for ophthalmic lenses, dispensing spectacles, and making and fitting contact lenses.

optico- optico-

See opto-.

opticociliary
opticociliary (op′ti-ko-sil′e-ar-e)

Relating to the optic and ciliary nerves.

opticopupillary
opticopupillary (op′ti-ko-pu′pi-lar-e)

Relating to the optic nerve and the pupil.

optics
optics (op′tiks)

The science concerned with the properties of light, its refraction and absorption, and the refracting media of the eye in that relation. [G. optikos, fr. ops, eye]
Nomarski o. an optical system for differential interference contrast microscopy.
schlieren o. an optical system, often used in diffusion and centrifugation studies, that observes the refractive index gradient in solutions containing macromolecules.

optimism
optimism (op′ti-mizm)

The tendency to look on the bright side of everything, to believe that there is good in everything. [L. optimus, best]
therapeutic o. a belief in the efficacy of drugs and other therapeutic agents in the treatment of diseases.

optimum
optimum (op′ti-mum)

The best or most suitable; e.g., denoting the dose of a remedy likely to give most benefit with fewest side effects, the temperature or pH at which an enzyme has maximal activity. [L. ntr. sing. of optimus, best]

opto- opto-, optico-

Optical; optic; ocular. [G. optikos, optical, from ops, eye]

optokinetic
optokinetic (op′to-ki-net′ik)

See o. nystagmus. [opto- + G. kinesis, movement]

optomeninx
optomeninx (op′to-me′ninks)

SYN: retina. [opto- + G. meninx, membrane]

optometer
optometer (op-tom′e-ter)

An instrument for determining the refraction of the eye. [opto- + G. metron, measure]
objective o. SYN: refractometer.

optometrist
optometrist (op-tom′e-trist)

One who practices optometry.

optometry
optometry (op-tom′e-tre)

1. The profession concerned with the examination of the eyes and related structures to determine the presence of vision problems and eye disorders and with the prescription and adaptation of lenses and other optical aids or the use of visual training for maximum visual efficiency. 2. The use of an optometer.

optomyometer
optomyometer (op′to-mi-om′e-ter)

An instrument for determining the relative power of the extrinsic muscles of the eye. [opto- + G. mys, muscle, + metron, measure]

optotypes
optotypes (op′to-tips)

Test letters. See test types. [opto- + G. typos, type]

OPV
OPV

Abbreviation for oral poliovirus vaccine. See poliovirus vaccines, under vaccine.

ora
ora, pl .orae (o′ra, o′re)

An edge or a margin. [L.]
o. serrata retinae the serrated extremity of the optic part of the retina, located a little behind the ciliary body and marking the limits of the percipient portion of the membrane.

ora
ora₁ (o′ra)

Plural of L. os, the mouth. [L.]

orad
orad (or′ad)

1. In a direction toward the mouth. 2. Situated nearer the mouth in relation to a specific reference point; opposite of aborad. [L. os, mouth, + ad, to]

oral
oral (or′al)

Relating to the mouth. [L. os (or-), mouth]

orale
orale (o-ra′le)

A point at the lingual side of the alveolar termination of the premaxillary suture. [Mod. L. punctum o., oral point, fr. L. os (or-), mouth]

Oral Hygiene Index
Oral Hygiene Index (OHI)

An index used in epidemiologic studies of dental disease to evaluate dental plaque and dental calculus separately.

orality
orality (or-al′i-te)

In freudian psychology, a term used to denote the psychic organization derived from, and characteristic of, the oral period of psychosexual development.

Oram
Oram

Samuel, 20th century English cardiologist. See Holt-O. syndrome.

orange
orange (or′enj)

1. The fruit of the o. tree, Citrus aurantium (family Rutaceae). 2. A color between yellow and red in the spectrum. For individual o. dyes, see specific name. [O.F. orenge, fr. Ar. naranj, the initial n being absorbed in Fr. article une]
bitter o. peel the dried rind of the unripe but fully grown fruit; a flavoring agent.
bitter o. peel, dried the dried outer part of the pericarp of the ripe, or nearly ripe, fruit; it contains not less than 2.5% v/w of volatile oil.
bitter o. peel, fresh the outer part of the pericarp of the ripe, or nearly ripe, fruit; used to prepare the tincture and the syrup.
bitter o. peel oil a volatile oil obtained by expression from the fresh peel of the bitter o..

orange G
orange G [C.I. 16230]

An azo dye, used as a cytoplasmic stain in histologic techniques.

orange wood
orange wood

A soft wood used in dentistry for placement of bridges, crowns, etc. by biting pressure, also used as a burnishing point in the polishing of root surfaces.

Orbeli
Orbeli

Leon A., Russian physiologist, 1882–1958. See O. effect.

orbicular
orbicular (or-bik′u-lar)

Similar in form to an orb; circular in form. [L. orbiculus, a small disk, dim. of orbis, circle]

orbiculare
orbiculare (or-bik-u-la′re)

SYN: lenticular process of incus. [L., fr. orbiculus, a small disk]

orbicularis
orbicularis (or-bik′u-la′ris)

1. Circular; denoting a circular or disk-shaped structure. 2. SYN: orbicular muscle. [L. fr. orbiculus, a small disk]

orbiculus ciliaris
orbiculus ciliaris (or-bik′u-lus sil-e-ar′is) [TA]

The darkly pigmented posterior zone of the ciliary body continuous with the retina at the ora serrata. SYN: ciliary disk, ciliary ring, pars plana. [Mod. L.]

orbit
orbit (or′bit) [TA]

The bony cavity containing the eyeball and its adnexa; it is formed of parts of seven bones: the frontal, maxillary, sphenoid, lacrimal, zygomatic, ethmoid, and palatine bones. SYN: orbita [TA] , eye socket, orbital cavity.

orbita
orbita, gen. orbitae (or′bi-ta, -te) [TA]

SYN: orbit. [L. a wheel-track, fr. orbis, circle]

orbital
orbital (or′bi-tal)

Relating to the orbits.

orbitale
orbitale (or-bi-ta′le)

In cephalometrics, the lowermost point in the lower margin of the bony orbit that may be felt under the skin. [L. of an orbit]

orbitography
orbitography (or′bi-tog′ra-fe)

Radiographic evaluation of the orbit. [L. orbita, orbit, + G. grapho, to write]
positive contrast o. o. with injection of a water soluble iodinated compound into the muscle cone or along the orbital floor.

orbitonasal
orbitonasal (or′bi-to-na′sal)

Relating to the orbit and the nose or nasal cavity.

orbitonometer
orbitonometer (or′bi-to-nom′e-ter)

An instrument that measures the resistance offered to pressing the eyeball backwards into its socket. [L. orbita, orbit, + G. metron, measure]

orbitonometry
orbitonometry (or′bi-to-nom′e-tre)

Measurement by means of the orbitonometer.

orbitopagus
orbitopagus (or-bi-top′a-gus)

Unequal conjoined twins in which the parasite, usually very imperfectly developed, is attached at an orbit of the autosite. See conjoined twins, under twin. SYN: teratoma orbitae. [L. orbita, orbit, + G. pagos, something fixed]

orbitopathy
orbitopathy

Disease of the orbit and its contents.
dysthyroid o. inflammation of the orbit in Graves disease.
Graves o. SYN: Graves ophthalmopathy.

orbitosphenoid
orbitosphenoid (or′bi-to-sfe′noyd)

Relating to the orbit and the sphenoid bone.

orbitotomy
orbitotomy (or-bi-tot′o-me)

Surgical incision into the orbit. [L. orbita, orbit, + tome, a cutting]

Orbivirus
Orbivirus (or′bi-vi-rus)

A genus of viruses of vertebrates (family Reoviridae) that multiply in arthropods, including certain viruses formerly included with the arboviruses. They are antigenically distinct from other groups of viruses and are characterized by an indistinct but rather large outer layer of capsomeres that give the appearance of rings (hence the name). The genus includes, among others, bluetongue virus of sheep and African horse sickness virus. [L. orbis, ring, + virus]

orcein
orcein (or′se-in) [old C.I. 1242]

A natural dye derived from orcinol by treatment with air and ammonia, which as a purple dye complex is used in various histologic staining methods.

orchalgia
orchalgia (ork-al′-je-a)

SYN: orchialgia.

orchectomy
orchectomy (or-kek′to-me)

SYN: orchiectomy.

orchella
orchella (or-kel′a) [old C.I. 1242]

SYN: archil.

orcheo- orcheo-

See orchio-.

orchi- orchi-, orchido-, orchio-

The testes. [G. orchis, testis]

orchialgia
orchialgia (or-ke-al′je-a)

Pain in the testis. SYN: orchalgia, orchiodynia, orchioneuralgia, testalgia. [orchi- + G. algos, pain]

orchichorea
orchichorea (or′ke-ko-re′a)

Involuntary rising and falling movements of the testis. [orchi- + G. choreia, a dance]

orchidectomy
orchidectomy (or-ki-dek′to-me)

SYN: orchiectomy.

orchidic
orchidic (or-kid′ik)

Relating to the testis.

orchiditis
orchiditis (or-ki-di′tis)

SYN: orchitis.

orchido- orchido-

See orchi-.

orchidometer
orchidometer (or-ki-dom′e-ter)

1. A caliper device used to measure the size of testes. 2. A set of sized models of testes for comparison of testicular development. [orchido- + G. metron, measure]

orchidopexy
orchidopexy (or-kid′o-peks-&maer;e)

SYN: orchiopexy.

orchidoptosis
orchidoptosis (or′ki-dop-to′sis)

Ptosis of the male gonads. [orchido- + G. ptosis, a falling]

orchidorraphy
orchidorraphy (or-ki-dor′a-fe)

SYN: orchiopexy.

orchiectomy
orchiectomy (or-ke-ek′to-me)

Removal of one or both testes. SYN: orchectomy, orchidectomy, testectomy. [orchi- + G. ektome, excision]

orchiepididymitis
orchiepididymitis (or′ke-ep′i-did′i-mi′tis)

Inflammation of the testis and epididymis. [orchi- + epididymis, + G. -itis, inflammation]

orchil
orchil (or′kil) [old C.I. 1242]

SYN: archil.

orchio- orchio-

See orchi-.

orchiocele
orchiocele (or′ke-o-sel)

A testis retained in the inguinal canal. [orchio- + G. kele, hernia, tumor]

orchiodynia
orchiodynia (or′ke-o-din′e-a)

SYN: orchialgia. [orchi- + G. odyne, pain]

orchioncus
orchioncus (or-ke-ong′kus)

A neoplasm of the testis. [orchio- + G. onkos, bulk, mass]

orchioneuralgia
orchioneuralgia (or′ke-o-noo-ral′je-a)

SYN: orchialgia. [orchio- + G. neuron, nerve, + algos, pain]

orchiopathy
orchiopathy (or-ke-op′a-the)

Disease of a testis. [orchio- + G. pathos, suffering]

orchiopexy
orchiopexy (or′ke-o-pek′se)

1. Surgical treatment of an undescended testicle by freeing it and implanting it into the scrotum. 2. Anchoring a testis susceptible to torsion in the scrotum. SYN: orchidopexy, orchidorraphy, orchiorrhaphy. [orchio- + G. pexis, fixation]
transseptal o. SYN: Ombrédanne operation.

orchioplasty
orchioplasty (or′ke-o-plas-te)

Surgical reconstruction of the testis. [orchio- + G. plastos, formed]

orchiorrhaphy
orchiorrhaphy (or-ke-or′a-fe)

SYN: orchiopexy. [orchio- + G. rhaphe, a suture]

orchiotherapy
orchiotherapy (or′ke-o-thar′a-pe)

Treatment with testicular extracts.

orchiotomy
orchiotomy (or-ke-ot′o-me)

Incision into a testis. SYN: orchotomy. [orchio- + G. tome, incision]

orchis
orchis, pl .orchises (or′kis, or′ki-sez)

SYN: testis. [G. testis, an orchid]

orchitic
orchitic (or-kit′ik)

Denoting orchitis.

orchitis
orchitis (or-ki′tis)

Inflammation of the testis. SYN: orchiditis, testitis. [orchi- + G. -itis, inflammation]
o. parotidea o. associated with mumps.
traumatic o. simple inflammation of the testis caused by mechanical injury.
o. variolosa o. complicating smallpox.

orchotomy
orchotomy (or-kot′o-me)

SYN: orchiotomy.

orcin
orcin (or′sin)

SYN: orcinol.

orcinol
orcinol (or′sin-ol)

3,5-Dihydroxytoluene;the parent substance of the natural dye orcein, obtained from certain colorless lichens (Lecanora tinctoria, Rocella tinctoria) by treatment with boiling water; used as an external antiseptic in various skin diseases and in chemistry as a reagent for pentoses. SYN: 5-methylresorcinol, orcin.

orciprenaline sulfate
orciprenaline sulfate (or-si-pren′a-len)

SYN: metaproterenol sulfate.

ORD
ORD

Abbreviation for optic rotatory dispersion.

Ord
Ord

Symbol for orotidine.

ordeal bean
ordeal bean (or′de-al)

SYN: physostigma.

order
order (or′der)

1. In biologic classification, the division just below the class (or subclass) and above the family. 2. In a reaction, o. is the sum of the exponents of all the concentration terms in that reaction's rate expression. For example, for the natural decomposition of nitrogen pentoxide, the rate expression is v = −d[N₂O₅]/dt = k₁[N₂O₅]. Thus, this is a first-o. reaction. A reaction involving two different compounds is often a second-o. reaction (but not necessarily so). Pseudo–first-o. reactions are multiorder reactions in which one of the reactants is in substoichiometric amounts. Cf.:molecularity. 3. The sequence of residues in a heteropolymer. [L. ordo, regular arrangement]
pecking o. in some species of birds and primates, the establishment of a graded dominance in members of a group by the use of aggression.

ordered
ordered (ord′erd)

SYN: o. mechanism.

orderly
orderly (or′der-le)

An attendant in a hospital unit who assists in the care of patients.

ordinate
ordinate (or′di-nat)

In a plane cartesian coordinate system, the vertical axis (y). Cf.:abscissa.

orectic
orectic (o-rek′tik)

Pertaining to or characterized by orexia.

orexia
orexia (o-rek′se-a)

1. The affective and conative aspects of an act, in contrast to the cognitive aspect. 2. SYN: appetite. [G. orexis, appetite]

orexigenic
orexigenic (o-rek-si-jen′ik)

Appetite stimulating.

orf
orf

A specific disease of sheep and goats, caused by the o. virus, family Poxviridae. This virus is transmissible to humans and characterized by vesiculation and ulceration of the infected site. SYN: contagious ecthyma, scabby mouth, soremouth. [O.E. orfcwealm, murrain, fr. o., cattle, + cwealm, destruction]

organ
organ (or′gan) [TA]

Any part of the body exercising a specific function, as of respiration, secretion, or digestion. SYN: organum [TA] , organon. [L. organum, fr. G. organon, a tool, instrument]
accessory organs 1. SYN: accessory structures, under structure. 2. SYN: supernumerary organs.
accessory organs of the eye SYN: accessory visual structures, under structure.
annulospiral o. SYN: annulospiral ending.
auditory o. archaic term for Corti o..
Chievitz o. a normal epithelial structure, possibly a neurotransmitter, found at the angle of the mandible with branches of the buccal nerve.
circumventricular organs four small areas in or near the base of the brain that have fenestrated capillaries and are outside the blood-brain barrier. They are neurohypophysis, area postrema [TA], organum vasculosum of lamina terminalis [TA], and subfornical o. [TA] (SFO). The neurohypophysis is a neurohemal o.. The other three are chemoreceptors: area postrema triggers vomiting in response to chemical changes in plasma, organum vasculosum of the lamina terminalis senses osmolality and alters vasopressin secretion, and SFO initiates drinking in response to angiotensin II.
Corti o. SYN: spiral o..
critical o. the o. or physiologic system that for a given source of radiation would first reach its legally defined maximum permissible radiation exposure as the dose of radiation is increased; e.g., the kidney is the critical o., receiving the most radiation, when Tc-99m dimethylsuccinic acid is given.
enamel o. a circumscribed mass of ectodermal cells budded off from the dental lamina; it becomes cup shaped and develops on its internal face the ameloblast layer of cells that produce the enamel cap of a developing tooth.
end o. the special structure containing the terminal of a nerve fiber in peripheral tissue such as muscle, tissue, skin, mucous membrane, or glands. SEE ALSO: ending.
external female genital organs SYN: female external genitalia.
external male genital organs SYN: male external genitalia.
floating o. SYN: wandering o..
flower-spray o. of Ruffini SYN: flower-spray ending.
genital organs SYN: genitalia.
Golgi tendon o. a proprioceptive sensory nerve ending embedded among the fibers of a tendon, often near the musculotendinous junction; it is compressed and activated by any increase of the tendon's tension, caused either by active contraction or passive stretch of the corresponding muscle. SYN: neurotendinous o., neurotendinous spindle.
gustatory o. [TA] located in the papillae of the mucous membrane of the tongue, chiefly in the vallate papillae. SYN: organum gustatorium [TA] , organum gustus [TA] , o. of taste.
o. of hearing SYN: cochlear labyrinth.
internal female genital organs SYN: female internal genitalia.
internal male genital organs SYN: male internal genitalia.
intromittent o. SYN: penis.
Jacobson o. SYN: vomeronasal o..
neurohemal organs brain areas from which substances enter blood e.g., the neurohypophysis from which oxytocin and vasopressin enter blood.
neurotendinous o. SYN: Golgi tendon o..
olfactory o. [TA] the olfactory region in the superior portion of the nasal cavity. SYN: organum olfactus [TA] , o. of smell.
otolithic organs the utricle and saccule of the inner ear that possess otoliths and respond to linear acceleration and deceleration, including gravity.
ptotic o. SYN: wandering o..
o. of Rosenmüller SYN: epoophoron.
sense organs [TA] the organs of special sense, including the eye, ear, olfactory o., taste organs, and the accessory structures associated with these organs. SYN: organa sensuum.
o. of smell SYN: olfactory o..
spiral o. [TA] a prominent ridge of highly specialized epithelium in the floor of the cochlear duct overlying the basilar membrane of cochlea, containing one inner row and three outer rows of hair cells, or cells of Corti (the auditory receptor cells innervated by the cochlear nerve) supported by various columnar cells: the pillars of Corti, cells of Hensen, and cells of Claudius; the spiral o. is partly overhung by an awninglike shelf, the tectorial membrane, the free marginal zone of which is covered by a gelatinous substance in which the stereocilia of the outer hair cells are embedded. SYN: organum spirale [TA] , acoustic papilla, Corti o..
subcommissural o. [TA] a microscopic o., made up of columnar ciliated ependymal cells, located in the cerebral aqueduct beneath the posterior commissure of the brain; it is believed to have a neurosecretory function. SYN: organum subcommissurale.
subfornical o. (SFO) the intercolumnar tubercle. One of the circumventricular organs. SFO has fenestrated capillaries and is outside the blood-brain barrier. It is thought to be a chemoreceptor zone involved in cardiovascular regulation. SYN: organum subformicale [TA] .
supernumerary organs organs exceeding the normal number, which may develop from multiple foci of organization in an o.-formative field larger (originally) than that of the definitive main o.; such organs are aberrant but frequently not a cause of disease; illness may persist if they are left in the body after therapeutic removal of the main o., e.g., accessory spleen. SYN: accessory organs (2) .
tactile o. SYN: o. of touch.
target o. a tissue or o. upon which a hormone exerts its action; generally, a tissue or o. with appropriate receptors for a hormone. SYN: target (3) .
o. of taste SYN: gustatory o..
o. of touch any one of the sensory end organs. SYN: organum tactus, tactile o..
urinary organs organs involved with the formation, storage, and excretion of urine. SEE ALSO: urinary system. SYN: organa urinaria.
vascular o. of lamina terminalis [TA] See circumventricular organs. SYN: organum vasculosum laminae terminalis [TA] .
vestibular o. SYN: vestibular labyrinth.
vestibulocochlear o. [TA] the external, middle, and internal ear. SYN: organum vestibulocochleare [TA] .
vestigial o. a rudimentary structure in humans corresponding to a functional structure or o. in the lower animals.
o. of vision SYN: visual o..
visual o. the eye and its adnexa. SYN: o. of vision, organum visus.
vomeronasal o. [TA] a fine vestigal horizontal canal, ending in a blind pouch, in the mucous membrane of the nasal septum, beginning just behind and above the incisive duct; a structure that usually regresses after the 6th month of gestation. In many lower animals, it functions as an accessory olfactory o.. SYN: organum vomeronasale [TA] , Jacobson o..
wandering o. an o. with loose attachments, permitting its displacement. SYN: floating o., ptotic o..
Weber o. SYN: prostatic utricle.
organs of Zuckerkandl SYN: paraaortic bodies, under body.

organa
organa (or′ga-na)

Plural of organum.

organelle
organelle (or′ga-nel)

One of the specialized parts of a protozoan or tissue cell; these subcellular units include mitochondria, the Golgi apparatus, nucleus and centrioles, granular and agranular endoplasmic reticulum, vacuoles, microsomes, lysosomes, plasma membrane, and certain fibrils, as well as plastids of plant cells. SYN: cell o., organoid (3) . [G. organon, organ, + Fr. -elle, dim. suffix, fr. L. -ella]
cell o. SYN: o..
paired organelles SYN: rhoptry.

organic
organic (or-gan′ik)

1. Relating to an organ. 2. Relating to or formed by an organism. 3. Organized; structural. 4. See o. compound. [G. organikos]

organicism
organicism (or-gan′i-sizm)

A theory that attributes all diseases, in particular, all mental disorders, as organic in origin.

organicist
organicist (or-gan′i-sist)

One who believes in, or subscribes to the views of, organicism.

organidin
organidin

SYN: iodinated glycerol.

organism
organism (or′ga-nizm)

Any living individual, whether plant or animal, considered as a whole.
calculated mean o. (CMO) a hypothetical o. whose characters are the means of both the positive and negative characters of the organisms which belong to the same taxon as the CMO, as opposed to the hypothetical mean. o..
defective o. SYN: auxotrophic mutant.
fastidious o. a bacterial o. having complex nutritional requirements.
hypothetical mean o. (HMO) a hypothetical o. whose characters are the means of the positive characters of the organisms which belong to the same taxon as the HMO, as opposed to the calculated mean o..
pleuropneumonia-like organisms (PPLO) the original name given to a group of bacteria that did not possess cell walls; these organisms, isolated from humans and other animals, soil, and sewage, are now assigned to the order Mycoplasmatales.

organization
organization (or′gan-i-za′shun)

1. An arrangement of distinct but mutually dependent parts. 2. The conversion of coagulated blood, exudate, or dead tissue into fibrous tissue.
health maintenance o. (HMO) a comprehensive prepaid system of health care intended to have emphasis on the prevention and early detection of disease, and continuity of care; often used synonymously with “managed care plan.”The term HMO refers to a health care delivery system characterized by multiplicity of services (primary care physicians and specialists, laboratory, radiology, pharmacy, and hospitalization); restriction of services to subscribers, and of benefits to participating health care providers, both typically confined to a certain geographic area; and an accounting system based on prepayment rather than fee for service. An HMO may be a nonprofit institution or a commercial venture. During the last quarter of the 20th century, HMOs emerged as an important alternative to traditional medical indemnity insurance plans, and largely supplanted them. HMOs have had a profound effect on every aspect of the practice of medicine: professional, scientific, social, economic, and legal. Some state legislatures, seeing the HMO's determining which medical services are appropriate in given circumstances as the practice of medicine, have passed laws rendering them liable to malpractice litigation. see also managed care.
preferred provider o. (PPO) a health care delivery model that uses a panel of eligible physicians.
pregenital o. in psychoanalysis, the o. or arrangement of the libido in the stages prior to that of genital primacy.

organize
organize (or′gan-iz)

To provide with, or to assume, a structure.

organizer
organizer (or′gan-i-zer)

1. Originally applied to a group of cells on the dorsal lip of the blastopore, which induce differentiation of cells in the embryo and control growth and development of adjacent parts. 2. Any group of cells having such a controlling influence, the effects being brought about through the action of an evocator.
nucleolar o. the region of the satellites on the acrocentric chromosomes that is active in nucleolus formation. SYN: nucleolar zone, nucleolus o..
nucleolus o. SYN: nucleolar o..
primary o. the o. situated on the dorsal lip of the blastopore.
procentriole o. SYN: deuterosome.

organo- organo-

Organ; organic. [G. organon]

organoaxial
organoaxial (or-ga′no-aks′e-al)

Rotation around the long axis of the organ; a type of gastric volvulus.

organoferric
organoferric (or′ga-no-far′ik)

Relating to an organic compound containing iron.

organogel
organogel (or-gan′o-jel)

A hydrogel with an organic liquid instead of water as the dispersion means.

organogenesis
organogenesis (or′ga-no-jen′e-sis)

Formation of organs during development. SYN: organogeny. [organo- + G. genesis, origin]

organogenetic
organogenetic, organogenic (or′ga-no-je-net′ik, -jen′ik)

Relating to organogenesis.

organogeny
organogeny (or-gan-oj′e-ne)

SYN: organogenesis.

organography
organography (or′ga-nog′ra-fe)

A treatise on, or description of, the organs of the body. [organo- + G. graphe, a writing]

organoid
organoid (or′ga-noyd)

1. Resembling in superficial appearance or in structure any of the organs or glands of the body. 2. Composed of glandular or organic elements and not of a single tissue; pertaining to certain neoplasms ( e.g., an adenoma) that contain cytologic and histologic elements arranged in a pattern that closely resembles or is virtually identical to a normal organ. SEE ALSO: histoid. 3. SYN: organelle. [organo- + G. eidos, resemblance]

organoleptic
organoleptic (or′ga-no-lep′tik)

1. Stimulating any of the organs of sensation. 2. Susceptible to a sensory stimulus. [organo- + G. leptikos, disposed to accept]

organology
organology (or-ga-nol′o-je)

Branch of science concerned with the anatomy, physiology, development, and functions of the various organs. SEE ALSO: splanchnology. [organo- + G. logos, study]

organomegaly
organomegaly (or′ga-no-meg′a-le)

SYN: visceromegaly.

organomercurial
organomercurial (or-gan′o-mer-ku′re-al)

Any organic mercurial compound; e.g., merbromin, thimerosal.

organometallic
organometallic (or′ga-no-me-tal′ik)

Denoting an organic compound containing one or more metallic atoms in its structure.

organon
organon, pl .organa (or′ga-non, or′ga-na)

SYN: organ. [G. organ]

organonomy
organonomy (or-ga-non′o-me)

The body of laws regulating the life processes of organized beings. [organo- + G. nomos, law]

organonymy
organonymy (or′ga-non′i-me)

The nomenclature of the organs of the body, as distinguished from toponymy. [organo- + G. onyma, name]

organopathy
organopathy (or-ga-nop′a-the)

Any disease especially affecting one of the organs of the body. [organo- + G. pathos, suffering]

organopexy
organopexy, organopexia (or′ga-no-pek-se, -pek′se-a)

Fixation by suture or otherwise of a floating or ptotic organ. [organo- + G. pexis, fixation]

organophilic
organophilic (or′ga-no-fil′ik)

Pertaining to organophilicity.

organophilicity
organophilicity (or′ga-no-fi-li′si-te)

Attraction of nonpolar substances (organic molecules) to each other.

organophosphates
organophosphates (or-ga-no-fos′fats)

A series of phosphorus-containing organic compounds usually also containing a halide ion that reacts with cholinesterase. O. phosphorylate cholinesterase and thus irreversibly inhibit it. Used as insecticides; have also been used as war gases.

organosol
organosol (or-gan′o-sol)

A hydrosol with an organic liquid instead of water as the dispersion means.

organotaxis
organotaxis (or′ga-no-tak′sis)

The tendency to migrate to a certain organ selectively. [organo- + G. taxis, orderly arrangement]

organotherapy
organotherapy (or′ga-no-thar′a-pe)

Treatment of disease by preparations made from animal organs; now frequently by synthetic preparations instead of extracts of a gland.

organotrophic
organotrophic (or′ga-no-trof′ik)

1. Pertaining to the nourishment of an organ. 2. Pertaining to a microorganism that uses organic sources as a reducing power. [organo- + G. trophe, nourishment]

organotropic
organotropic (or′ga-no-trop′ik)

Pertaining to or characterized by organotropism.

organotropism
organotropism (or-ga-not′ro-pizm)

The special affinity of particular drugs, pathogens, or metastatic tumors for particular organs or their component parts. Cf.:parasitotropism. SYN: organotropy. [organo- + G. trope, a turning]

organotropy
organotropy (or-ga-not′ro-pe)

SYN: organotropism.

organ-specific
organ-specific

1. Denoting or pertaining to a serum produced by the injection of the cells of a certain organ or tissue that, when injected into another animal, destroys the cells of the corresponding organ. 2. Denoting an antigen specific for a particular organ.

organum
organum, pl .organa (or′ga-num, or′ga-na) [TA]

SYN: organ, organ. [L. tool, instrument]
o. auditus archaic term for vestibulocochlear organ.
organa genitalia [TA] SYN: genitalia.
organa genitalia feminina externa SYN: female external genitalia.
organa genitalia feminina interna SYN: female internal genitalia.
organa genitalia masculina externa SYN: male external genitalia.
organa genitalia masculina interna SYN: male internal genitalia.
o. gustatorium [TA] SYN: gustatory organ.
o. gustus [TA] SYN: gustatory organ.
organa oculi accessoria SYN: accessory visual structures, under structure.
o. olfactus [TA] SYN: olfactory organ.
organa sensuum SYN: sense organs, under organ.
o. spirale [TA] SYN: spiral organ.
o. subcommissurale SYN: subcommissural organ.
o. subformicale [TA] SYN: subfornical organ. See circumventricular organs, under organ.
o. tactus SYN: organ of touch.
organa urinaria SYN: urinary organs, under organ.
o. vasculosum laminae terminalis [TA] SYN: vascular organ of lamina terminalis. See circumventricular organs, under organ.
o. vestibulocochleare [TA] SYN: vestibulocochlear organ.
o. visus SYN: visual organ.
o. vomeronasale [TA] SYN: vomeronasal organ.

orgasm
orgasm (or′gazm)

The acme of the sexual act. SYN: climax (2) . [G. orgao, to swell, be excited]

orgasmic
orgasmic, orgastic (or-gaz′mik, -gas′tik)

Relating to, characteristic of, or tending to produce an orgasm.

orientation
orientation (or-e-en-ta′shun)

1. The recognition of one's temporal, spatial, and personal relationships and environment. 2. The relative position of an atom with respect to one to which it is connected, i.e., the direction of the bond connecting them. [Fr. orienter, to set toward the East, therefore in a definite position]
sexual o. concept that includes the permutations among body morphology, gender identity, gender role, and sexual preference.

Orientia
Orientia (or-e-en′-a)

A member of the bacterial family Rickettsiae.
O. tsutsugamushi the only member of its genus, this species is the causative agent of scrub typhus, transmitted by mites; formerly called Rickettsia tsutsugamushi.

orientomycin
orientomycin (or′e-en-to-mi′sin)

SYN: cycloserine.

orifice
orifice (or′i-fis) [TA]

Any aperture or opening. SEE ALSO: aperture, opening, os, ostium, meatus. SYN: orificium [TA] . [L. orificium]
anal o. SYN: anus.
aortic o. [TA] the opening from the left ventricle into the ascending aorta; it is guarded by the aortic valve. SYN: ostium aortae [TA] , aortic ostium.
cardiac o. SYN: cardial o..
cardial o. [TA] the trumpet-shaped opening of the esophagus into the stomach. SYN: ostium cardiacum [TA] , cardiac opening, cardiac o., esophagogastric o..
esophagogastric o. SYN: cardial o..
o. of external acoustic meatus SYN: external acoustic pore.
external urethral o. [TA] 1. the slitlike opening of the urethra in the glans penis; 2. the external o. of the urethra (in the female) in the vestibule, usually upon a slight elevation, the papilla urethrae. SYN: ostium urethrae externum [TA] , external urinary meatus&star, external opening of urethra, meatus urinarius, orificium urethrae externum.
filling internal urethral o. [TA] the internal urethral o. once the bladder begins to be distended with urine, when the trigonal muscles are contracted and the detrusor muscle is relaxed; during this stage the o. occurs at a higher level, and is bounded by a different portion of the mucosa, than during voiding. SEE ALSO: voiding internal urethral o.. SYN: ostium urethrae internum accipiens [TA] .
gastroduodenal o. SYN: pyloric o..
golf-hole ureteral o. a circular and often escessively lateral ureteral o. that may be associated with vesicoureteral reflux, previous bladder surgery, or tuberculosis.
ileal o. [TA] the opening of the terminal ileum into the large intestine at the transition between the cecum and the ascending colon. SYN: ostium ileale [TA] , o. of ileal papilla&star, ileocecal opening, ileocecal o., ostium ileocecale.
o. of ileal papilla ileal o..
ileocecal o. SYN: ileal o..
o. of inferior vena cava SYN: opening of inferior vena cava.
o. of internal acoustic meatus SYN: internal acoustic pore.
internal urethral o. [TA] the internal opening or o. of the urethra, at the anterior and inferior angle of the trigone. SYN: ostium urethrae internum [TA] , internal urethral opening&star.
left atrioventricular o. [TA] an atrioventricular opening that leads from the left atrium into the left ventricle of the heart. SYN: ostium atrioventriculare sinistrum [TA] , mitral o., ostium arteriosum.
mitral o. SYN: left atrioventricular o..
pulmonary o. SYN: opening of pulmonary trunk.
pyloric o. [TA] the opening between the stomach and the superior part of the duodenum. SYN: ostium pyloricum [TA] , gastroduodenal o..
right atrioventricular o. [TA] an atrioventricular opening that leads from the right atrium into the right ventricle of the heart. SYN: ostium atrioventriculare dextrum [TA] , ostium venosum cordis, tricuspid o..
root canal o. an opening in the pulp chamber leading to the root canal.
o. of superior vena cava SYN: opening of superior vena cava.
tricuspid o. SYN: right atrioventricular o..
ureteric o. [TA] the opening of the ureter in the bladder, situated one at each lateral angle of the trigone; wide gaping of the ostium usually indicates vesicoureteral reflux. SYN: ostium ureteris [TA] , orificium ureteris, ureteral meatus, ureteral opening.
o. of uterus SYN: external os of uterus.
vaginal o. [TA] the narrowest portion of the canal, in the floor of the vestibule posterior to the urethral o.. SYN: ostium vaginae [TA] , orificium vaginae, vaginal opening.
o. of vermiform appendix [TA] the opening of the vermiform appendix into the lumen of the cecum. SYN: ostium appendicis vermiformis [TA] , ostium of vermiform appendix.
voiding internal urethral o. [TA] the internal urethral o. when the bladder is being emptied of urine, when the trigonal muscles are relaxed and the detrusor muscle is contracting; during this stage the o. occurs at a lower level, and is bounded by a different portion of the mucosa, than during filling and reserving. SEE ALSO: filling internal urethral o.. SYN: ostium urethrae internum evacuans [TA] .

orificial
orificial (or-i-fish′al)

Relating to an orifice of any kind.

orificium
orificium, pl .orificia (or-i-fish′e-um, -a) [TA]

SYN: orifice, orifice. [L.]
o. externum uteri SYN: external os of uterus.
o. internum uteri SYN: isthmus of uterus.
o. ureteris SYN: ureteric orifice.
o. urethrae externum SYN: external urethral orifice.
o. vaginae SYN: vaginal orifice.

origanum oil
origanum oil (o-rig′a-num)

The volatile oil (which contains carvacrol) obtained from various species of Origanum (family Labiatae); used as a rubefacient, as a constituent in veterinary liniments, and in microscopic techniques.

origin
origin (or′i-jin)

1. The less movable of the two points of attachment of a muscle, that which is attached to the more fixed part of the skeleton. 2. The starting point of a cranial or spinal nerve. The former have two origins: the ental o., deep o., or real o., the cell group in the brain or medulla, whence the fibers of the nerve begin, and the ectal o., superficial o., or apparent o., the point where the nerve emerges from the brain. [L. origo, source, beginning, fr. orior, to rise]
o. of replication a sequence of the bacterial genome required for the initiating of a replicating fork by leading strand synthesis.

orizaba jalap root
orizaba jalap root (o-riz′a-ba ja′lap)

SYN: ipomea.

Ormond
Ormond

John K., U.S. urologist, *1886. See O. disease.

Orn
Orn

Symbol for ornithine or its radical.

ornate
ornate (or′nat)

A term that refers to the patterning of the scutum (gray or white markings on a dark background) in ixodid ticks. [L. ornatus, decorated]

Ornish
Ornish

Dean, U.S. physician, *1953. See O. reversal diet.

ornithine
ornithine (Orn) (or′ni-then, -thin)

2,5-Diaminovaleric acid;the l-isomer is the amino acid formed when l-arginine is hydrolyzed by arginase; not a constituent of proteins, but an important intermediate in the urea cycle; elevated levels seen in certain defects of the urea cycle.
o. acetyltransferase SYN: glutamate acetyltransferase.
o. δ-aminotransferase an enzyme that will reversibly catalyze the reaction of α-ketoglutarate and l-o. to form l-glutamate and l-glutamate γ-semialdehyde; a deficiency of this enzyme will result in gyrate atrophy of the choroid and retina. SYN: o. transaminase.
o. carbamoyltransferase an enzyme catalyzing formation of l-citrulline and orthophosphate from l-o. and carbamoyl phosphate; a part of the urea cycle; a deficiency of this enzyme will result in ammonia intoxication and impaired urea formation. SYN: o. transcarbamoylase.
o. decarboxylase an enzyme catalyzing the decarboxylation of l-o. to putrescine and CO₂; first step in polyamine biosynthesis.
o. transaminase SYN: o. δ-aminotransferase.
o. transcarbamoylase SYN: o. carbamoyltransferase.

ornithinemia
ornithinemia (or′ni-thi-ne′me-a)

A toxic condition occasionally producing localized cerebral swelling, caused by abnormal amounts of ornithine in the blood. [ornithine + G. haima, blood]

ornithinuria
ornithinuria (or′ni-thi-noo′re-a)

Excretion of excessive amounts of ornithine in the urine.

Ornithodoros
Ornithodoros (or-ni-thod′o-rus)

A genus of soft ticks (family Argasidae), several species of which are vectors of pathogens of various relapsing fevers. They are characterized by a capitulum hidden below the hood and by disks and mamillae of the integument that are continuous from dorsal to ventral surfaces in a variety of patterns. [G. ornis (ornith-), bird, + doros, a leather bag]
O. coriaceus a tick species common in the mountainous coastal areas of California; adults readily attack deer, cattle, and humans, and have an irritating, painful, sometimes toxic bite. Transmits epizootic bovine abortion to cattle. SYN: pajaroello.
O. erraticus a species of tick the small variety of which is the vector of Borrelia crocidurae in Africa, the Near East, and Central Asia; the large variety is the vector of B. hispanica in the Spanish peninsula and adjacent north Africa.
O. hermsi a tick species that is a rodent parasite and vector of relapsing fever spirochetes, such as Borrelia hermsii, in the western U.S. and Canada.
O. lahorensis a species of tick that may transmit Borrelia persica, the agent of Persian relapsing fever.
O. moubata complex a group of four tick species in Africa; the taxonomy and ecology of this complex is of great significance because its members are vectors of relapsing fever spirochetes; members of the complex include O. moubata (various hosts), O. compactus (tortoises), O. apertus (porcupines), and O. porcinus (warthogs); a domestic subspecies of O. porcinus, in turn, forms three strains that feed chiefly on humans, fowl, and swine.
O. pappilipes the “Persian bug,” a tick species found in Central Asia and the Near East that transmits Borrelia persica, the pathogen in Iran of Persian relapsing fever.
O. parkeri a tick species found in the western U.S. and a vector of Borrelia parkeri.
O. rudis a tick species that is an important vector of relapsing fever spirochetes in Central and South America; possibly another complex similar to the O. moubata complex.
O. savigni a tick species transmitting Borrelia, an agent of relapsing fever of eastern Africa, southern Egypt, Ethiopia, and southwestern Asia.
O. talajé a tick species found in Mexico and in Central and South America, where it feeds on wild rodents, domestic animals, and humans; it delivers a painful, irritating bite and is a vector of Borrelia mazzottii, a cause of relapsing fever.
O. tholozani a species of tick that transmits Borrelia persica, an agent of relapsing fever in the Middle East and central Asia.
O. turicata a species of tick that readily attacks humans and other animals in the southern portion of the U.S. and Mexico; it is a vector of Borrelia turicatae, an agent of relapsing fever; the bite is painful and irritating.
O. venezuelensis a tick species that is the vector of Borrelia venezuelensis, agent of relapsing fever in Colombia, Venezuela, and mountainous parts of South America.
O. verrucosus a tick species, the vector of Borrelia caucasica.

Ornithonyssus
Ornithonyssus (or-ni-thon′i-sus)

A genus of bird and rodent mites; species include O. bacoti, the tropical rat mite, a possible vector of murine typhus and a cause of human dermatitis; O. bursa, the tropical fowl mite; and O. sylviarum, the northern fowl mite. [G. ornis (ornith-), bird, + nyssus, to prick]

ornithosis
ornithosis (or-ni-tho′sis)

Originally, a disease in nonpsittacine birds (domestic fowl, ducks, pigeons, turkeys, and many wild birds) caused by Chlamydia psittaci; now, generally referred to as psittacosis. [G. ornis (ornith-), bird, + -osis, condition]

Oro
Oro

Symbol for orotic acid or orotate.

oro- oro-

1. The mouth. [L. os, oris, mouth] 2. Obsolete alternative spelling is orrho-. See sero-. [G. orrhos, whey, serum]

orodigitofacial
orodigitofacial (or′o-dij′i-to-fa′shal)

Relating to the mouth, fingers, and face.

orofacial
orofacial (or-o-fa′shal)

Relating to the mouth and face.

orolingual
orolingual (or-o-ling′gwal)

Relating to the mouth and tongue.

oronasal
oronasal (or-o-na′sal)

Relating to the mouth and nose.

oropharyngeal
oropharyngeal (or-o-fa-rin′je-al)

Relating to the oropharynx.

oropharynx
oropharynx (or′o-far′ingks) [TA]

The portion of the pharynx that lies posterior to the mouth; it is continuous above with the nasopharynx via the pharyngeal isthmus and below with the laryngopharynx. SYN: pars oralis pharyngis [TA] , oral part of pharynx, oral pharynx. [L. os (or-), mouth]

orosomucoid
orosomucoid (or′o-so-mu′koyd)

α₁-Acid glycoprotein;a subgroup of the α₁-globulin fraction of blood; increased plasma levels are associated with inflammation. SYN: α₁-acid glycoprotein, acid seromucoid.

orotate
orotate (Oro) (or′o-tat)

A salt or ester of orotic acid.
o. phosphoribosyltransferase a phosphoribosyltransferase synthesizing orotidylate and pyrophosphate from o. and 5-phospho-α-d-ribosyl-1-pyrophosphate; this enzyme is a part of pyrimidine biosynthesis; a deficiency of this enzyme is associated with orotic aciduria type I. Cf.:uridylic acid synthase. SYN: OMP pyrophosphorylase, orotidylic acid phosphorylase, orotidylic acid pyrophosphorylase.

orotic acid
orotic acid (Oro) (or-ot′ik)

6-Carboxyuracil; uracil-6-carboxylic acid;an important intermediate in the formation of the pyrimidine nucleotides; elevated in certain inherited defects of pyrimidine biosynthesis. SYN: uracil-6-carboxylic acid.

orotic aciduria
orotic aciduria [MIM*258900]

A rare disorder of pyrimidine metabolism characterized by hypochromic anemia with megaloblastic changes in bone marrow, leukopenia, retarded growth, and urinary excretion of orotic acid; autosomal recessive inheritance, caused by mutation in the uridine monophosphatate synthase gene (MMPS) on 3q13. [orotic acid + G. ouron, urine]

orotidine
orotidine (O, Ord) (o-rot′i-den)

Orotic acid-3-β-d-ribonucleoside; uridine-6-carboxylic acid;elevated in cases of orotidinuria. SYN: 1-ribosylorotate.
o. 5′-monophosphate (OMP) SYN: orotidylic acid.

orotidinuria
orotidinuria (o-rot′i-den-u′re-a)

Elevated levels of orotidine in the urine; has been observed in defects in and inhibition of orotidylic acid decarboxylase.

orotidylate
orotidylate (OMP) (o-rot-i-dil′at)

A salt or ester of orotidylic acid.

orotidylic acid
orotidylic acid (OMP) (o-rot-i-dil′ik)

Orotidine 5′-monophosphate;an intermediate in the biosynthesis of the pyrimidine nucleosides (cytidine and uridine) that are found in nucleic acids. SYN: orotidine 5′-monophosphate.
o. decarboxylase an enzyme that catalyzes the conversion of OMP to UMP and CO₂; a defect or inhibition of this enzyme will result in orotic aciduria and orotidinuria; this enzyme is a part of pyrimidine biosynthesis. Cf.:uridylic acid synthase. SYN: OMP decarboxylase.
o. phosphorylase SYN: orotate phosphoribosyltransferase.
o. pyrophosphorylase SYN: orotate phosphoribosyltransferase.

orphan
orphan (or′fan)

See o. products, under product. [G. orphanos]

orphenadrine citrate
orphenadrine citrate (or-fen′a-dren)

An antihistaminic that also has the same action and use as orphenadrine hydrochloride.

orphenadrine hydrochloride
orphenadrine hydrochloride

It reduces spasm of voluntary muscles, probably by action on the cerebral motor areas; used in the symptomatic treatment of paralysis agitans and drug-induced parkinsonism.

orrho- orrho-

Serum. See sero-. [G. orrhos, oros, whey, serum]

orris
orris (or′is)

SYN: iris.

Orsi
Orsi

Francesco, Italian physician, 1828–1890. See O.-Grocco method.

Orth
Orth

Johannes J., German pathologist, 1847–1923. See O. fixative, O. stain.

orth- orth-

See ortho-.

orthesis
orthesis (or-the′sis)

Rarely used term for an orthopedic brace, splint, or appliance. [ortho- + -esis, process]

orthetics
orthetics (or-thet′iks)

SYN: orthotics.

ortho- ortho-, orth-

1. Prefix denoting straight, normal, in proper order. 2. (o-) In chemistry, italicized prefix denoting that a compound has two substitutions on adjacent carbon atoms in a benzene ring. For terms beginning o. or o-, see the specific name. 3. The most hydrated of a series of oxoacids, e.g., orthophosphoric acid, H₃PO₄. [G. orthos correct]

orthoacid
orthoacid (or′tho-as′id)

An acid in which the number of hydroxyl groups equals the valence of the acid-forming element; e.g., C(OH)₄, orthocarbonic acid. When there is no such acid, the one that most nearly approaches this condition is sometimes called an o.; e.g., OP(OH)₃, orthophosphoric acid.

orthocaine
orthocaine (or′tho-kan)

The methyl ester of 3-amino-4-hydroxybenzoic acid; a surface anesthetic agent usually used in dusting powder form.

orthocephalic
orthocephalic (or′tho-se-fal′ik)

Having a head well proportioned to height; denoting a skull with a vertical index between 70 and 75. SEE ALSO: metriocephalic. SYN: orthocephalous. [ortho- + G. kephale, head]

orthocephalous
orthocephalous (or-tho-sef′a-lus)

SYN: orthocephalic.

orthochromatic
orthochromatic (or′tho-kro-mat′ic)

Denoting any tissue or cell that stains the color of the dye used, i.e., the same color as the dye solution with which it is stained. SYN: euchromatic (1) , orthochromophil, orthochromophile. [ortho- + G. chroma, color]

orthochromophil
orthochromophil, orthochromophile (or-tho-kro′mo-fil, -fil)

SYN: orthochromatic. [ortho- + G. chroma, color, + philos, fond]

orthocrasia
orthocrasia (or-tho-kra′se-a)

Obsolete term for condition in which there is a normal reaction to drugs, articles of diet, etc. [ortho- + G. krasis, a mixing, temperament]

orthocytosis
orthocytosis (or′tho-si-to′sis)

A condition in which all of the cellular elements in the circulating blood are mature forms, irrespective of the proportions of various types and total numbers. [ortho- + G. kytos, cell, + -osis, condition]

orthodentin
orthodentin (or-tho-den′tin)

Straight tubed dentin as seen in the teeth of mammals.

orthodeoxia
orthodeoxia

Fall in arterial blood oxygen upon assuming the upright posture. Usually caused by right-to-left cardiac or vascular shunting with a posturally induced fall in left-sided pressure permitting a corresponding gradient across the shunt.

orthodigita
orthodigita (or-tho-dij′i-tah)

Correction of malformations of fingers or toes. [ortho- + L. digitus, finger or toe]

orthodontia
orthodontia (or-tho-don′she-a)

SYN: orthodontics.

orthodontics
orthodontics (or-tho-don′tiks)

That branch of dentistry concerned with the correction and prevention of irregularities and malocclusion of the teeth. SYN: dental orthopedics, orthodontia. [ortho- + G. odous, tooth]
surgical o. the correction of occlusal abnormalities by the surgical repositioning of segments of the mandible or maxillae containing one to several teeth; or the bodily repositioning of entire jaws to improve function and esthetics. SYN: orthognathic surgery.

orthodontist
orthodontist

A dental specialist who practices orthodontics.

orthodromic
orthodromic (or-tho-dro′mik)

Denoting the propagation of an impulse along a conduction system ( e.g., nerve fiber) in the direction it normally travels. Cf.:antidromic. [ortho- + G. dromos, course]

orthogenesis
orthogenesis (or-tho-jen′e-sis)

The doctrine that evolution is governed by intrinsic factors and occurs in predictable directions. [ortho- + G. genesis, origin]

orthogenic
orthogenic (or-tho-jen′ik)

Relating to orthogenesis.

orthogenics
orthogenics (or-tho-jen′iks)

SYN: eugenics.

orthognathia
orthognathia (or-tho-nath′e-a, or-thog-nath′e-&brev;a)

The study of the causes and treatment of conditions related to malposition of the bones of the jaws. [ortho- + G. gnathos, jaw]

orthognathic
orthognathic, orthognathous (or-tho-nath′ik, or-thog′nathus)

1. Relating to orthognathia. 2. Having a face without projecting jaw, one with a gnathic index below 98. [ortho- + G. gnathos, jaw]

orthograde
orthograde (or′tho-grad)

Walking or standing erect; denoting the posture of humans; opposed to pronograde. [ortho- + L. gradior, pp. gressus, to walk]

orthokeratology
orthokeratology (or′tho-ker-a-tol′o-je)

A method of molding the cornea with contact lenses to improve unaided vision. [ortho- + G. keras, horn (cornea), + logos, science]

orthokeratosis
orthokeratosis (or′tho-ker-a-to′sis)

Formation of an anuclear keratin layer, as in the normal epidermis. [ortho- + G. keras, horn, + -osis, condition]

orthokinetics
orthokinetics (or-tho-ki-net′iks)

A method advocated for the treatment of hypertrophic osteoarthritis in which an attempt is made to change muscular action from one group of muscles to another set of muscles to protect the diseased joint. [ortho- + G. kinetikos, movable, fr. kineo, to move]

orthomechanical
orthomechanical (or-tho-me-kan′i-kal)

Pertaining to braces, prostheses, orthotic devices, and appliances. [ortho- + mechanical]

orthomechanotherapy
orthomechanotherapy (or′tho-me-kan-o-thar′a-pe)

Treatment with braces, prostheses, orthotic devices, or appliances. [ortho- + G. mechane, machine, + therapeia, medical treatment]

orthomelic
orthomelic (or-tho-me′lik)

Correcting malformations of arms or legs. [ortho- + G. melos, limb]

orthometer
orthometer (or-thom′e-ter)

SYN: exophthalmometer. [ortho- + G. metron, measure]

orthomolecular
orthomolecular (or′tho-mo-lek′u-lar)

L.C. Pauling term denoting a therapeutic approach designed to provide an optimum molecular environment for body functions, with particular reference to the optimum concentrations of substances normally present in the human body, whether formed endogenously or ingested.

Orthomyxoviridae
Orthomyxoviridae (or′tho-mik-so-vir′i-de)

The family of viruses that contains the 3 genera of influenza viruses, types A and B, C, and “Thogoto-like viruses.” Virions are roughly spherical or filamentous, and the former (the more common form) are 80–120 mm in diameter and ether-sensitive; envelopes are studded with surface projections; nucleocapsids are of helical symmetry, 6–9 nm in diameter, and contain single-stranded, segmented RNA. The nucleoprotein antigen of each type of virus is common to all strains of the type but is distinct from those of the other types; the mosaic of surface antigens varies from strain to strain. Nucleocapsids seem to be formed in the nuclei of infected cells, hemagglutinin, and neuraminidase in the cytoplasm; virus maturation occurs during budding of the cell membrane. Influenza virus types A and B are subject to mutation resulting in epidemics. Influenza virus C differs from types A and B ( e.g., lacks neuraminidase) and belongs to a separate genus. SEE ALSO: Influenza virus.

orthopaedic
orthopaedic, orthopedic (or-tho-pe′dik)

Relating to orthopedics.

orthopaedics
orthopaedics (or-tho-pe′diks)

SYN: orthopedics. [ortho- + G. pais (paid-), child]

orthopaedist
orthopaedist, orthopedist (or-tho-pe′dist)

One who practices orthopaedics.

orthopedics
orthopedics

The medical specialty concerned with the preservation, restoration, and development of form and function of the musculoskeletal system, extremities, spine, and associated structures by medical, surgical, and physical methods. SYN: orthopaedics.
dental o. SYN: orthodontics.
functional jaw o. utilization of muscle forces to effect changes in jaw position and tooth alignment by removable appliances. SYN: functional orthodontic therapy.

orthopercussion
orthopercussion (or′tho-per-kush′un)

Very light percussion of the chest, made in a sagittal direction ( i.e., anteroposteriorly, and not perpendicularly to the wall of the chest); used to determine the size of the heart, with the faint percussion sound disappearing when the heart is reached, even though that may be overlapped by a layer of the lung.

orthophoria
orthophoria (or-tho-for′e-a)

Absence of heterophoria; the condition of binocular fixation in which the lines of sight meet at a distant or near point of reference in the absence of a fusion stimulus. [ortho- + G. phora, motion]

orthophoric
orthophoric (or-tho-for′ik)

Pertaining to orthophoria.

orthophosphate
orthophosphate (or-tho-fos′fat)

A salt or ester of orthophosphoric acid.
inorganic o. (P_i) any ion or salt form of phosphoric acid. SYN: inorganic phosphate.

orthophosphoric acid
orthophosphoric acid (or′tho-fos-for′ik)

Phosphoric acid, O&dbond;P(OH)₃, distinguished by ortho- from meta- and pyrophosphoric acids, (HPO₃)_n and OP(OH₂)OP(OH)₂O, respectively, which are anhydrides of H₃PO₄; the ultimate anhydride is phosphorus pentoxide, P₂O₅.

orthophrenia
orthophrenia (or-tho-fre′ne-a)

1. Rarely used term for soundness of mind. 2. Rarely used term for a condition of normal interpersonal relationships. [ortho- + G. phren, mind]

orthopnea
orthopnea (or-thop-ne′a, or-thop′ne-a)

Discomfort in breathing that is brought on or aggravated by lying flat. Cf.:platypnea. [ortho- + G. pnoe, a breathing]

orthopneic
orthopneic (or′thop-ne′ik)

Relating to or characterized by orthopnea.

Orthopoxvirus
Orthopoxvirus (or-tho-poks′vi-rus)

The genus of the family Poxviridae, which comprises the viruses of alastrim, vaccinia, variola, cowpox, ectromelia, monkeypox, and rabbitpox.

orthoprosthesis
orthoprosthesis (or′tho-pros′the-sis, -pros-the′sis)

An appliance used in the management of prosthetic problems related to alignment of teeth.

orthopsychiatry
orthopsychiatry (or′tho-si-ki′a-tre)

A cross-disciplinary science combining child psychiatry, developmental psychology, pediatrics, and family care devoted to the discovery, prevention, and treatment of mental and psychological disorders in children and adolescents.

Orthoptera
Orthoptera (or-thop′ter-a)

A large order of hemimetabolous insects that includes the locusts, grasshoppers, mantids, walking sticks, and related forms. [ortho- + G. pteron, a wing]

orthoptic
orthoptic (or-thop′tik)

Relating to orthoptics.

orthoptics
orthoptics (or-thop′tiks)

The study and treatment of defective binocular vision, of defects in the action of the ocular muscles, or of faulty visual habits. [ortho- straightened + G. optikos, sight]

orthoptist
orthoptist (or-thop′tist)

One skilled in orthoptics.

Orthoreovirus
Orthoreovirus (or-tho-re′o-vi-rus)

A genus in the family Reoviridae associated with a variety of respiratory and enteric diseases, but its causal relationship is not proven.

orthoscope
orthoscope (or′tho-skop)

1. An instrument by means of which one is able to draw the outlines of the various normas of the skull. [ortho- + G. skopeo, to view]

orthosis
orthosis, pl .orthoses (or-tho′sis, -sez)

An external orthopaedic appliance, as a brace or splint, that prevents or assists movement of the spine or the limbs. [G. o., a making straight]
ankle-foot o. an o. beginning at the toes, crossing the ankle, and terminating on the calf.
cervical o. an o. designed to limit cervical spine motion to varying degrees, e.g., a soft cervical collar.
cervicothoracic o. a device designed to limit cervical spine motion by extending to cover more of the upper torso than a standard cervical o..
knee-ankle-foot o. an o. extending from the upper portion of the thigh, crossing the knee and ankle, and terminating at the toes; designed to control knee and ankle motion.
thoracolumbosacral o. an external device applied to the trunk and extending from the upper portion of the thoracic spine to the pelvis; designed to provide immobilization of the thoracic spine.
wrist-hand o. an o. that begins at the fingers, crosses the wrist, and terminates on the distal portion of the forearm; used to provided grasp and release despite some degree of hand paralysis.

orthostatic
orthostatic (or-tho-stat′ik)

Relating to an erect posture or position.

orthostereoscope
orthostereoscope (or′tho-ster′e-o-skop)

A rarely used instrument for viewing stereoscopic radiographs.

orthothanasia
orthothanasia (or′tho-tha-na′ze-a)

1. A normal or natural manner of death and dying. 2. Sometimes used to denote the deliberate stopping of artificial or heroic means of maintaining life. [ortho- + G. thanatos, death]

orthotics
orthotics (or-thot′iks)

The science concerned with the making and fitting of orthopaedic appliances. SYN: orthetics.

orthotist
orthotist (or′tho′tist)

A maker and fitter of orthopaedic appliances.

orthotolidine
orthotolidine (or-tho-to′li-den)

In the presence of peroxidase, o. (like benzidine) is oxidized to a blue color; because hemoglobin behaves like a peroxidase, o. has been used as an in vitro aid for the detection of occult blood in feces.

orthotonos
orthotonos, orthotonus (or-thot′o-nos, -o-nus)

A form of tetanic spasm in which the neck, limbs, and body are held fixed in a straight line. [ortho- + G. tonos, tension]

orthotopic
orthotopic (or-tho-top′ik)

In the normal or usual position. [ortho- + G. topos, place]

orthotropic
orthotropic (or-tho-trop′ik)

Extending or growing in a straight, especially a vertical, direction. [ortho- + G. trope, a turn]

orthovoltage
orthovoltage (or-tho-vol′tij)

In radiation therapy, a term for voltage between 400 and 600 kV.

Ortolani
Ortolani

Marius, 20th century Italian orthopaedic surgeon. See O. maneuver, O. test.

Orton
Orton

Samuel T., U.S. neurologist, 1879–1975. See Wolf-O. bodies, under body.

orycenin
orycenin (or-e-sen′in)

A glutelin in rice. [G. oryza, rice, + -in]

O.S.
O.S.

Abbreviation for L. oculus sinister, left eye.

Os
Os

Symbol for osmium.

os
os, gen. oris, pl .ora

1. [NA] The mouth. 2. Term applied sometimes to an opening into a hollow organ or canal, especially one with thick or fleshy edges. SEE ALSO: mouth (2) , ostium, orifice, opening. [L. mouth]
anatomical internal o. of uterus [TA] aperture at the narrowing of the uterine cavity demarcating and providing communication between the lumina of the body (uterine cavity) and of the cervix (cervical canal) of the uterus. SYN: ostium anatomicum [TA] .
external o. of uterus [TA] the vaginal opening of the uterus. SYN: ostium uteri [TA] , mouth of the womb, opening of uterus, orifice of uterus, orificium externum uteri, o. uteri externum, ostium uteri externum.
histological internal o. of uterus [TA] site of transition of mucosa of uterus (endometrium) to that of the cervix; it may or may not correspond to the anatomic internal o.. SYN: ostium histologicum [TA] .
incompetent cervical o. a defect in the strength of the internal o. allowing premature dilation of the cervix.
ossa pedis [TA] SYN: bones of foot, under bone.
o. uteri externum SYN: external o. of uterus.
o. uteri internum SYN: isthmus of uterus.

os
os, gen. ossis, pl .ossa (os, os′is, os′a) [TA]

SYN: bone.For histologic description, see bone. [L. bone]
o. acromiale an acromion that is joined to the scapular spine by fibrous rather than by bony union.
o. basilare SYN: basilar bone.
o. breve [TA] SYN: short bone.
o. calcis SYN: calcaneus (1) .
o. capitatum [TA] SYN: capitate (1) .
ossa carpi [TA] SYN: carpal bones, under bone.
o. centrale [TA] a small bone occasionally found at the dorsal aspect of the wrist between the scaphoid, capitate, and trapezoid; it is developed as an independent cartilage in early fetal life but usually becomes fused with the scaphoid; it occurs normally in most monkeys. SYN: central bone.
o. centrale tarsi SYN: navicular.
o. clitoridis a small bone located in the clitoris of many carnivorous mammals. It is homologous with the o. penis of many male mammals.
o. coccygis [TA] SYN: coccyx.
o. costale SYN: Rib.
o. coxae [TA] SYN: hip bone.
ossa cranii [TA] SYN: bones of cranium, under bone.
o. cuboideum SYN: cuboid (bone).
o. cuneiforme intermedium SYN: intermediate cuneiform (bone).
o. cuneiforme laterale [TA] SYN: lateral cuneiform (bone).
o. cuneiforme mediale [TA] SYN: medial cuneiform (bone).
ossa digitorum bones of digits, under bone. SEE ALSO: phalanx (1) .
o. ethmoidale [TA] SYN: ethmoid.
ossa faciei SYN: facial bones, under bone.
o. femoris thigh.
o. frontale [TA] SYN: frontal bone.
o. hamatum SYN: hamate (bone).
o. hyoideum SYN: hyoid bone. SEE ALSO: hyoid apparatus.
o. iliacum SYN: ilium.
o. ilium [TA] SYN: ilium.
o. incae SYN: interparietal bone.
o. incisivum [TA] SYN: incisive bone.
o. innominatum SYN: hip bone.
o. intermaxillare SYN: incisive bone.
o. intermedium SYN: lunate (bone).
o. intermetatarseum a supernumerary bone at the base of the first metatarsal, or between the first and second metatarsal bones, usually fused with one or the other or with the medial cuneiform bone. SYN: intermetatarseum.
o. interparietale [TA] SYN: interparietal bone.
o. irregulare [TA] SYN: irregular bone.
o. ischii [TA] SYN: ischium.
o. japonicum a bipartite or tripartite zygomatic bone, found with greater frequency in the Japanese than in other races.
o. lacrimale [TA] SYN: lacrimal bone.
o. longum [TA] SYN: long bone.
o. lunatum [TA] SYN: lunate (bone).
o. magnum SYN: capitate (1) .
o. malare SYN: zygomatic bone.
ossa membri inferioris [TA] SYN: bones of lower limb, under bone.
ossa membri superioris [TA] SYN: bones of upper limb, under bone.
ossa metacarpalia I–V SYN: metacarpal (bones) [I–V], under bone.
ossa metacarpi, pl .ossa metacarpalia [TA] SYN: metacarpal (bones) [I–V], under bone.
ossa metatarsalia I–V SYN: metatarsal (bones) [I–V], under bone.
ossa metatarsi, pl .ossa metatarsalia [TA] SYN: metatarsal (bones) [I–V], under bone.
o. multangulum majus SYN: trapezium bone.
o. multangulum minus SYN: trapezoid (bone).
o. nasale [TA] SYN: nasal bone.
o. naviculare [TA] SYN: navicular.
o. naviculare manus SYN: scaphoid (bone).
o. occipitale [TA] SYN: occipital bone.
o. odontoideum the dens of the axis when anomalously not fused with the body of the axis.
o. orbiculare SYN: lenticular process of incus.
o. palatinum [TA] SYN: palatine bone.
o. parietale [TA] SYN: parietal bone.
o. pisiforme [TA] SYN: pisiform (bone).
o. planum [TA] SYN: flat bone.
o. pneumaticum [TA] SYN: pneumatized bone.
o. premaxillare SYN: incisive bone.
o. pterygoideum SYN: pterygoid process of sphenoid bone.
o. pubis SYN: pubis.
o. pyramidale SYN: triquetrum.
o. sacrum [TA] SYN: sacrum.
o. scaphoideum [TA] SYN: scaphoid (bone).
o. sesamoideum, pl .ossa sesamoidea [TA] SYN: sesamoid bone.
o. sphenoidale [TA] SYN: sphenoid (bone).
o. subtibiale an inconstant bone found very rarely in the distal articular end of the tibia.
ossa suprasternalia [TA] SYN: suprasternal bones, under bone.
o. suturarum [TA] SYN: sutural bones, under bone.
o. sylvii SYN: lenticular process of incus.
ossa tarsalia tarsal bones, under bone.
ossa tarsi [TA] SYN: tarsal bones, under bone.
o. temporale [TA] SYN: temporal bone.
o. tibiale posterius, o. tibiale posticum a sesamoid bone in the tendon of the tibialis posterior muscle, occasionally fused with the tuberosity of the navicular. SYN: tibiale posticum.
o. trapezium SYN: trapezium bone.
o. trapezoideum [TA] SYN: trapezoid (bone).
o. triangulare SYN: triquetrum.
o. tribasilare the single bone resulting from the fusion in infancy of the occipital and temporal bones at the base of the cranial cavity.
o. trigonum [TA] an independent ossicle sometimes present in the tarsus; usually it forms part of the talus, constituting the lateral tubercle of the posterior process. SYN: triangular bone.
o. triquetrum [TA] SYN: triquetrum.
o. unguis SYN: lacrimal bone.
o. vesalianum the tuberosity of the fifth metatarsal bone sometimes existing as a separate bone. SYN: vesalianum, Vesalius bone.
o. zygomaticum [TA] SYN: zygomatic bone.

osazone
osazone (o′sa-zon)

The compound formed by certain sugars ( e.g., glucose, galactose, fructose) with excess hydrazines, possessing two hydrazones on carbons 1 and 2 instead of only one at C-1, as in the ordinary hydrazone, thus, RNH&cbond;N&dbond;CR′&cbond;CR&dprime;&dbond;N&cbond;NHR&dprime;′; osazones formed with phenylhydrazine (phenylosazones) are used to characterize and identify certain sugars. SYN: dihydrazone.

osche- osche-, oscheo-

The scrotum. [G. osche]

oscheal
oscheal (os′ke-al)

SYN: scrotal.

oscheoplasty
oscheoplasty (os′ke-o-plas-te)

SYN: scrotoplasty. [oscheo- + plastos, formed]

oscillation
oscillation (os-i-la′shun)

1. A to-and-fro movement. 2. A stage in the vascular changes in inflammation in which the accumulation of leukocytes in the small vessels arrests the passage of blood and there is simply a to-and-fro movement at each cardiac contraction. [L. oscillatio, fr. oscillo, to swing]

oscillator
oscillator (os′si-la-ter)

1. An apparatus somewhat like a vibrator, used to give a form of mechanical massage. 2. An electric circuit designed to generate alternating current at a particular frequency. 3. Any device that produces oscillation.

oscillograph
oscillograph (o-sil′o-graf)

An instrument that records oscillations, usually electrical.

oscillography
oscillography (os-i-log′ra-fe)

The study of the records made by an oscillograph.

oscillometer
oscillometer (os-i-lom′e-ter)

An apparatus for measuring oscillations of any kind, especially those of the bloodstream in sphygmometry. SEE ALSO: sphygmo-o.. [L. oscillo, to swing, + G. metron, measure]

oscillometric
oscillometric (os′i-lo-met′rik)

Relating to the oscillometer or the records made by its use.

oscillometry
oscillometry (os-i-lom′e-tre)

The measurement of oscillations of any kind with an oscillometer.

oscillopsia
oscillopsia (os-i-lop′se-a)

The subjective sensation of oscillation of objects viewed. SYN: oscillating vision. [L. oscillo, to swing, + G. opsis, vision]

oscilloscope
oscilloscope (o-sil′o-skop)

An oscillograph in which the record of oscillations is continuously visible.
cathode ray o. (CRO) the common form of o., in which a varying electrical signal (y) vertically deflects an electron beam impinging on a fluorescent screen, while some other function (x or time) deflects the beam horizontally; the result is a visual graph of y plotted against x or time with negligible distortion by inertia.
storage o. a cathode ray o. in which the visual record of oscillations persists on the fluorescent screen until erased electrically.

oscitate
oscitate (os′i-tat)

To yawn; to gape. [L. oscito, fr. os, mouth, + cieo, to put in motion]

oscitation
oscitation (os′i-ta′shun)

SYN: yawning. [L. oscitatio]

osculum
osculum, pl .oscula (os′ku-lum, -la)

A pore or minute opening. [L. dim. of os, mouth]

-ose -ose

1. In chemistry, a terminator usually indicating a carbohydrate. 2. Suffix appended to some Latin roots, with significance of the more common -ous (2) . [L. -osus, full of, abounding]

-oses -oses

Plural of -osis.

Osgood
Osgood

Robert B., U.S. orthopedic surgeon, 1873–1956. See O.-Schlatter disease.

OSHA
OSHA

Abbreviation for Occupational Safety and Health Administration of the U.S. Department of Labor, responsible for establishing and enforcing safety and health standards in the workplace.

-osis -osis, pl .-oses

Suffix meaning a process, condition, or state, usually abnormal or diseased; production or increase, physiologic or pathologic; an invasion or infestation; in the latter sense, it is similar to and often interchangeable with Greek -iasis, as seen in trichinosis, trichiniasis. [G.]

Osler
Osler

Sir William, Canadian physician in U.S. and England, 1849–1919. See O. disease, O. node, O. sign, Rendu-O.-Weber syndrome.

osmate
osmate (os′mat)

A salt of osmic acid.

osmatic
osmatic (oz-mat′ik)

SYN: olfactory. [G. osme, smell]

OSMED
OSMED

SYN: chondrodystrophy with sensorineural deafness.

osmesis
osmesis (oz-me′sis)

SYN: olfaction. [G. o., smelling]

osmic acid
osmic acid (oz′mik)

OsO₄;a volatile caustic and strong oxidizing agent; colorless crystals, poorly soluble in water, but soluble in organic solvents; the aqueous solution is a fat and myelin stain and a general fixative for electron microscopy. SYN: osmium tetroxide.

osmicate
osmicate (oz′mi-kat)

To stain or fix with osmic acid.

osmication
osmication, osmification (os′mi-ka′shun, os′mi-fi-ka′shun)

The fixation of tissue with an osmic acid solution; also serves as a stain for both light and electron microscopy.

osmics
osmics (oz′miks)

The science of olfaction. [G. osme, smell]

osmiophilic
osmiophilic (oz′mi-o-fil′ik)

Readily stained with osmic acid. [osmium + G. phileo, to love]

osmiophobic
osmiophobic (oz′mi-o-fo′bik)

Not readily stained with osmic acid. [osmium + G. phobos, fear]

osmium
osmium (Os) (oz′me-um)

A metallic element of the platinum group, atomic no. 76, atomic wt. 190.2. [G. osme, smell, because of the strong odor of the tetroxide]
o. tetroxide SYN: osmic acid.

osmo- osmo-

1. Osmosis. [G. osmos, impulsion] 2. Smell, odor. [G. osme]

osmoceptor
osmoceptor (os-mo-sep′ter, tor)

SYN: osmoreceptor.

osmodysphoria
osmodysphoria (oz′mo-dis-for′e-a)

An abnormal dislike of certain odors. [G. osme, smell, + dys-, bad, + phora, a carrying]

osmogram
osmogram (oz′mo-gram)

SYN: electroolfactogram. [G. osme, smell, + gramma, a drawing]

osmolality
osmolality (os-mo-lal′i-te)

The concentration of a solution expressed in osmoles of solute particles per kilogram of soluent.
calculated serum o. the calculation of serum o. from serum sodium, glucose, and urea nitrogen values by a variety of formulae, the most common of which is: 1.86 × [Na] (mmol/L + glucose (mg/dL)/18 + BUN (mg/dL)/2.8.

osmolar
osmolar (os-mo′lar)

SYN: osmotic.

osmolarity
osmolarity (os-mo-lar′i-te)

The osmotic concentration of an osmotically active substance in solution, expressed as osmoles of solute particles per liter of solution.

osmole
osmole (os′mol)

The molecular weight of a solute, in grams, divided by the number of ions or particles into which it dissociates in solution.

osmology
osmology (os-mol′o-je)

1. The study of odors, their production, and their effects. SYN: osphresiology. 2. The study of osmosis.

osmometer
osmometer (os-mom′e-ter)

1. An instrument for measuring osmolality by freezing point depression or vapor pressure elevation techniques. 2. An apparatus for measuring the acuteness of the sense of smell.

osmometry
osmometry (os-mom′e-tre)

Measurement of osmolality by use of an osmometer.

osmophil
osmophil, osmophilic (os′mo-fil, -fil′ik)

Flourishing in a medium of high osmotic pressure. [osmo(sis) + G. phileo, to love]

osmophobia
osmophobia (oz-mo-fo′be-a)

SYN: olfactophobia. [G. osme, smell, + phobia]

osmophore
osmophore (oz′mo-for)

The group of atoms in the molecule of a compound that is responsible for the compound's characteristic odor. [G. osme, smell, + phonos, bearing]

osmoreceptor
osmoreceptor (os′mo-re-sep′ter, -tor)

1. A receptor in the central nervous system (probably the hypothalamus) that responds to changes in the osmotic pressure of the blood. [G. osmos, impulsion] 2. A receptor that receives olfactory stimuli. [G. osme, smell] SYN: osmoceptor.

osmoregulatory
osmoregulatory (os-mo-reg′u-la-tor-e)

Influencing the degree and rapidity of osmosis.

osmose
osmose (os′mos)

To move through a membrane by osmosis.

osmosis
osmosis (os-mo′sis)

The process by which solvent tends to move through a semipermeable membrane from a solution of lower to a solution of higher osmolal concentration of the solutes to which the membrane is relatively impermeable. [G. osmos, a thrusting, an impulsion]
reverse o. movement of solvent in the opposite direction from o., i.e., pressure filtration of solvent through a semipermeable membrane that will hold back the solutes; commonly replaced by filtration or ultrafiltration when speaking of capillary membranes, as in the renal glomerulus.

osmosity
osmosity (os-mos′i-te)

An indirect measure of the osmotic characteristics of a solution, in terms of a comparable sodium chloride solution, now rendered obsolete by the more precisely defined term osmolality.

osmotherapy
osmotherapy (os′mo-thar′a-pe)

Dehydration by means of intravenous injections of hypertonic solutions of sodium chloride, dextrose, urea, mannitol, or other osmotically active substances, or by oral administration of glycerine, isosorbide, glycine, etc.; used in the treatment of cerebral edema and increased intracranial pressure. [osmosis + therapy]

osmotic
osmotic (os-mot′ik)

Relating to osmosis. SYN: osmolar.

osphresio- osphresio-

Odor; sense of smell. [G. osphresis, smell]

osphresiologic
osphresiologic (os-fre-ze-o-loj′ik)

Relating to osphresiology.

osphresiology
osphresiology (os-fre′ze-ol′o-je)

SYN: osmology (1) . [osphresio- + G. logos, study]

osphresiophilia
osphresiophilia (os-fre′ze-o-fil′e-a)

An unusual interest in odors. [osphresio- + G. phileo, to love]

osphresiophobia
osphresiophobia (os-fre′ze-o-fo′be-a)

SYN: olfactophobia. [osphresio- + G. phobos, fear]

osphresis
osphresis (os-fre′sis)

SYN: olfaction. [G. o., smell]

osphretic
osphretic (os-fret′ik)

SYN: olfactory.

ossa
ossa (os′a)

Plural of L. os, bone. [L.]

ossein
ossein, osseine (os′e-in)

SYN: collagen. [L. os, bone]

osseo- osseo-

Bony. SEE ALSO: ossi-, osteo-. [L. osseus]

osseocartilaginous
osseocartilaginous (os′e-o-kar-ti-laj′i-nus)

Relating to, or composed of, both bone and cartilage. SYN: osteocartilaginous, osteochondrous.

osseomucin
osseomucin (os′e-o-mu′sin)

The ground substance of bony tissue.

osseomucoid
osseomucoid (os′e-o-mu′koyd)

A mucoid derived from ossein.

osseous
osseous (os′e-us)

Bony, of bone-like consistency or structure. SYN: osteal. [L. osseus]

ossi- ossi-

Bone. SEE ALSO: osseo-, osteo-. [L. os]

ossicle
ossicle (os′i-kl) [TA]

A small bone; specifically, one of the bones of the tympanic cavity or middle ear. SYN: ossiculum [TA] , bonelet. [L. ossiculum, dim. of os, bone]
Andernach ossicles SYN: sutural bones, under bone.
auditory ossicles [TA] the small bones of the middle ear; they are articulated to form a chain for the transmission of sound from the tympanic membrane to the oval window. SYN: ossicula auditus [TA] , ear bones, ossicular chain.
Bertin ossicles SYN: sphenoidal conchae, under concha.
epactal ossicles SYN: sutural bones, under bone.
Kerckring o. SYN: Kerckring center.

ossicula
ossicula (o-sik′u-la)

Plural of ossiculum. [L.]

ossicular
ossicular (o-sik′u-lar)

Pertaining to an ossicle.

ossiculectomy
ossiculectomy (os′i-ku-lek′to-me)

Removal of one or more of the ossicles of the middle ear. [L. ossiculum, ossicle, + G. ektome, excision]

ossiculotomy
ossiculotomy (os′i-ku-lot′o-me)

Division of one of the ossicles of the middle ear. [L. ossiculum, ossicle, + G. tome, incision]

ossiculum
ossiculum, pl .ossicula (o-sik′u-lum, -la) [TA]

SYN: ossicle. [L. dim. of os, bone]
ossicula auditus [TA] SYN: auditory ossicles, under ossicle.
ossicula mentalia small nodules of bone that appear at the symphysis menti shortly before birth and fuse with the mandible after birth.

ossiferous
ossiferous (o-sif′er-us)

Containing or producing bone. [ossi- + L. fero, to bear]

ossific
ossific (o-sif′ik)

Relating to a change into, or formation of, bone.

ossification
ossification (os′i-fi-ka′shun)

1. The formation of bone. 2. A change into bone. [L. ossificatio, fr. os, bone, + facio, to make]
endochondral o. formation of osseous tissue by the replacement of calcified cartilage; long bones grow in length by endochondral o. at the epiphysial cartilage plate where osteoblasts form bone trabeculae on a framework of calcified cartilage.
intramembranous o. SYN: membranous o..
membranous o. development of osseous tissue within mesenchymal tissue without prior cartilage formation, such as occurs in the frontal and parietal bones. SYN: intramembranous o..
metaplastic o. the formation of irregular foci of bone (sometimes including bone marrow) in various soft structures, such as the muscles, lungs, brain, and other sites where osseous tissue is abnormal.

ossiform
ossiform (os′i-form)

SYN: osteoid (1) . [ossi- + L. forma, form]

ossify
ossify (os′i-fi)

To form bone or convert into bone. [ossi- + L. facio, to make]

ost- ost-

See osteo-.

osteal
osteal (os′te-al)

SYN: osseous. [G. osteon, bone]

ostealgia
ostealgia (os-te-al′je-a)

Pain in a bone. SYN: osteodynia. [osteo- + G. algos, pain]

osteanagenesis
osteanagenesis (os′te-an-a-jen′e-sis)

SYN: osteoanagenesis.

osteanaphysis
osteanaphysis (os′te-a-naf′i-sis)

SYN: osteoanagenesis. [osteo- + G. anaphysis, a growing again]

ostectomy
ostectomy (os-tek′to-me)

1. Surgical removal of bone. 2. In dentistry, resection of supporting osseous structure to eliminate periodontal pockets. SYN: osteoectomy. [osteo- + G. ektome, excision]

ostein
ostein, osteine (os′te-in)

SYN: collagen. [G. osteon, bone]

osteitic
osteitic (os-te-it′ik)

Relating to or affected by osteitis. SYN: ostitic.

osteitis
osteitis (os-te-i′tis)

Inflammation of bone. SYN: ostitis. [osteo- + G. -itis, inflammation]
alveolar o. SYN: alveoalgia.
caseous o. tuberculous caries in bone.
central o. 1. SYN: osteomyelitis. 2. SYN: endosteitis.
o. condensans ilii (con-den′sanz il′e-i) symmetric benign osteosclerosis of the portion of the iliac bones adjacent to the sacroiliac joints.
condensing o. SYN: sclerosing o..
cortical o. periostitis with involvement of the superficial layer of bone.
o. deformans SYN: Paget disease (1) .
o. fibrosa circumscripta SYN: monostotic fibrous dysplasia.
o. fibrosa cystica increased osteoclastic resorption of calcified bone with replacement by fibrous tissue, caused by primary hyperparathyroidism or other causes of the rapid mobilization of mineral salts. SYN: parathyroid osteosis, Recklinghausen disease of bone.
o. fibrosa disseminata SYN: polyostotic fibrous dysplasia.
focal condensing o. SYN: chronic focal sclerosing osteomyelitis.
hematogenous o. any o. caused by infection carried in the bloodstream.
localized o. fibrosa SYN: monostotic fibrous dysplasia.
multifocal o. fibrosa SYN: polyostotic fibrous dysplasia.
o. pubis osteosclerosis of the pubic bone next to the symphysis, caused by trauma to that region, from pregnancy or instrumentation.
renal o. fibrosa SYN: renal rickets.
sclerosing o. fusiform thickening or increased density of bones, of unknown cause; it has been considered a form of chronic nonsuppurative osteomyelitis. SYN: condensing o., Garré disease.
o. tuberculosa multiplex cystica an o. of tuberculous origin, marked by numerous small cavities in the osseous substance. SYN: Jüngling disease.

ostemia
ostemia (os-te′me-a)

Congestion or hyperemia of a bone. [osteo- + G. haima, blood]

ostempyesis
ostempyesis (os′tem-pi-e′sis)

Suppuration in bone. [osteo- + G. empyesis, suppuration]

osteo- osteo-, ost-, oste-

Bone. SEE ALSO: osseo-, ossi-. [G. osteon]

osteoanagenesis
osteoanagenesis (os′te-o-an-a-jen′e-sis)

Regeneration of bone. SYN: osteanagenesis, osteanaphysis. [osteo- + G. ana, again, + genesis, generation]

osteoarthritis
osteoarthritis (os′te-o-ar-thri′tis)

Arthritis characterized by erosion of articular cartilage, either primary or secondary to trauma or other conditions, which becomes soft, frayed, and thinned with eburnation of subchondral bone and outgrowths of marginal osteophytes; pain and loss of function result; mainly affects weight-bearing joints, is more common in older persons. SYN: arthrosis (2) , degenerative arthritis, degenerative joint disease, osteoarthrosis.
hyperplastic o. SYN: hypertrophic pulmonary osteoarthropathy.

osteoarthropathy
osteoarthropathy (os′te-o-ar-throp′a-the)

A disorder affecting bones and joints. [osteo- + G. arthron, joint, + pathos, suffering]
hypertrophic pulmonary o. expansion of the distal ends, or the entire shafts, of the long bones, sometimes with erosions of the articular cartilages and thickening and villous proliferation of the synovial membranes, and frequently clubbing of fingers; the disorder occurs in some chronic pulmonary diseases, in heart disease (most often congenital), and occasionally in other acute and chronic disorders. SYN: Bamberger-Marie disease, Bamberger-Marie syndrome, hyperplastic osteoarthritis, pneumogenic o., pulmonary o..
idiopathic hypertrophic o. o. not secondary to pulmonary or other progressive lesions, which may occur alone (acropathy) or as part of the syndrome of pachydermoperiostosis.
pneumogenic o. SYN: hypertrophic pulmonary o..
pulmonary o. SYN: hypertrophic pulmonary o..

osteoarthrosis
osteoarthrosis (os′te-o-ar-thro′sis)

SYN: osteoarthritis. [osteo- + G. arthron, joint, + -osis, condition]

osteoblast
osteoblast (os′te-o-blast)

A bone-forming cell that is derived from mesenchymal osteoprognitor cells and forms an osseous matrix in which it becomes enclosed as an osteocyte. SYN: osteoplast. [osteo- + G. blastos, germ]

osteoblastic
osteoblastic (os′te-o-blas′tik)

Relating to the osteoblasts; describes any region of increased radiographic bone density, in particular, metastases that stimulate o. activity.

osteoblastoma
osteoblastoma (os′te-o-blas-to′ma)

An uncommon benign tumor of osteoblasts with areas of osteoid and calcified tissue, occurring most frequently in the spine of a young person. SYN: giant osteoid osteoma.

osteocalcin
osteocalcin

A protein found in osteoblasts and dentin; contains γ-carboxyglutamyl residues; has a role in mineralization and calcium ion homeostasis. SYN: bone Gla protein.

osteocartilaginous
osteocartilaginous (os′te-o-kar-ti-laj′i-nus)

SYN: osseocartilaginous.

osteochondritis
osteochondritis (os′te-o-kon-dri′tis)

Inflammation of a bone and its overlying articular cartilage. [osteo- + G. chondros, cartilage, + -itis, inflammation]
o. deformans juvenilis SYN: Legg-Calvé-Perthes disease.
o. deformans juvenilis dorsi SYN: Scheuermann disease.
o. dissecans complete or incomplete separation of a portion of joint cartilage and underlying bone, usually involving the knee, associated with epiphyseal aseptic necrosis.
syphilitic o. inflammation of the epiphysial line associated with congenital syphilis. SYN: Wegner disease.

osteochondrodysplasia
osteochondrodysplasia

SYN: camptomelic syndrome.

osteochondrodystrophia deformans
osteochondrodystrophia deformans (os′te-o-kon′dro-dis-tro′fe-a de-for′manz)

SYN: chondro-osteodystrophy.

osteochondrodystrophy
osteochondrodystrophy (os′te-o-kon′dro-dis′tro-fe)

SYN: chondro-osteodystrophy.

osteochondroma
osteochondroma (os′te-o-kon-dro′ma)

A benign cartilaginous neoplasm that consists of a pedicle of normal bone (protruding from the cortex) covered with a rim of proliferating cartilage cells; may originate from any bone that is preformed in cartilage, but is most frequent near the ends of long bones, usually in patients 10–25 years of age; the lesion is frequently not noticed, unless it is traumatized or of large size; multiple osteochondromas are inherited and referred to as hereditary multiple exostoses. SYN: solitary osteocartilaginous exostosis. [osteo- + G. chondros, cartilage, + -oma, tumor]

osteochondromatosis
osteochondromatosis (os′te-o-kon-dro-ma-to′-sis)

SYN: hereditary multiple exostoses, under exostosis.
synovial o. SYN: synovial chondromatosis.

osteochondrosarcoma
osteochondrosarcoma (os′te-o-kon′dro-sar-ko′-ma)

Chondrosarcoma arising in bone. Sarcomas in bone containing foci of neoplastic cartilage as well as bone are classified as osteogenic sarcomas. [osteo- + G. chondros, cartilage, + sarx, flesh, + -oma, tumor]

osteochondrosis
osteochondrosis (os′te-o-kon-dro′sis)

Any of a group of disorders of one or more ossification centers in children, characterized by degeneration or aseptic necrosis followed by reossification; includes the various forms of epiphysial aseptic necrosis. [osteo- + G. chondros, cartilage, + -osis, condition]

osteochondrous
osteochondrous (os′te-o-kon′drus)

SYN: osseocartilaginous. [osteo- + G. chondros, cartilage]

osteoclasis
osteoclasis, osteoclasia (os′te-ok′la-sis, os′te-o-kla′ze-a)

Intentional fracture of a bone to correct deformity. SYN: diaclasis, diaclasia. [osteo- + G. klasis, fracture]

osteoclast
osteoclast (os′te-o-klast)

1. A large multinucleated cell, possibly of monocytic origin, with abundant acidophilic cytoplasm, functioning in the absorption and removal of osseous tissue. SYN: osteophage. 2. An instrument used to fracture a bone to correct a deformity. [osteo- + G. klastos, broken]

osteoclastic
osteoclastic (os′te-o-klas′tik)

Pertaining to osteoclasts, especially with reference to their activity in the absorption and removal of osseous tissue.

osteoclastoma
osteoclastoma (os′te-o-klas-to′ma)

SYN: giant cell tumor of bone.

osteocranium
osteocranium (os′te-o-kra′ne-um)

The cranium of the fetus after ossification of the membranous cranium has made it firm. [osteo- + G. kranion, skull]

osteocystoma
osteocystoma (os′te-o-sis-to′ma)

SYN: solitary bone cyst.

osteocyte
osteocyte (os′te-o-sit)

A cell of osseous tissue that occupies a lacuna and has cytoplasmic processes that extend into canaliculi and make contact by means of gap junctions with the processes of other osteocytes. SYN: bone cell, bone corpuscle, osseous cell. [osteo- + G. kytos, cell]

osteodentin
osteodentin (os′te-o-den′tin)

Rapidly formed tertiary dentin that contains entrapped odontoblasts and few dentinal tubules, thereby superficially resembling bone. [osteo- + L. dens, tooth]

osteodermatopoikilosis
osteodermatopoikilosis (os′te-o-der′ma-to-poy-ki-lo′sis) [MIM*166700]

Osteopoikilosis with skin lesions, most commonly small elastic fibrous nodules on the posterior aspects of the thighs and buttocks; irregular autosomal dominant inheritance. SYN: Buschke-Ollendorf syndrome. [osteo- + G. derma, skin, + poikilos, dappled, + -osis, condition]

osteodesmosis
osteodesmosis (os′te-o-dez-mo′sis)

Transformation of tendon into bony tissue. [osteo- + G. desmos, a band (tendon), + -osis, condition]

osteodiastasis
osteodiastasis (os′te-o-di-as′ta-sis)

Separation of two adjacent bones, as of the cranium. [osteo- + G. diastasis, a separation]

osteodynia
osteodynia (os-te-o-din′e-a)

SYN: ostealgia. [osteo- + G. odyne, pain]

osteodysplasty
osteodysplasty (os′te-o-dis′plas-te)

SYN: Melnick-Needles o.. SYN: Melnick-Needles syndrome. [osteo- + G. dys-, bad, + plastos, formed]
Melnick-Needles o. a generalized skeletal dysplasia with prominent forehead and small mandible; radiographically, there are irregular ribbonlike constrictions of the ribs and tubular bones; probably X-linked [MIM*309350]. Autosomal dominant and recessive inheritance [MIM*249420] have also been suggested. SYN: o..

osteodystrophia
osteodystrophia (os′te-o-dis-tro′fe-a)

SYN: osteodystrophy.

osteodystrophy
osteodystrophy (os′te-o-dis′tro-fe)

Defective formation of bone. SYN: osteodystrophia. [osteo- + G. dys, difficult, imperfect, + trophe, nourishment]
Albright hereditary o. an inherited form of hyperparathyroidism associated with ectopic calcification and ossification and skeletal defects, notably the small fourth metacarpals; intelligence may be normal or subnormal. Inheritance is heterogeneous; the autosomal form [MIM*103580] is caused by mutation in the guanine nucleotide-binding protein gene (GNAS1) on 20q. There are also the recessive [MIM*203330] and X-linked [MIM*300800] forms. SEE ALSO: pseudohypoparathyroidism. SYN: Albright syndrome (2) .
renal o. generalized bone changes resembling osteomalacia and rickets or osteitis fibrosa, occurring in children or adults with chronic renal failure.

osteoectomy
osteoectomy (os-te-o-ek′to-me)

SYN: ostectomy.

osteoepiphysis
osteoepiphysis (os′te-o-e-pif′i-sis)

An epiphysis of a bone.

osteofibroma
osteofibroma (os′te-o-fi-bro′ma)

A benign lesion of bone, probably not a true neoplasm, consisting chiefly of fairly dense, moderately cellular, fibrous connective tissue in which there are small foci of osteogenesis. Most examples of this condition, especially in the maxilla and mandible, probably represent foci of fibrous dysplasia; a few examples of fibrous lesions with foci of osteogenesis, especially in vertebral bodies, may be neoplasms.

osteofibrosis
osteofibrosis (os′te-o-fi-bro′sis)

Fibrosis of bone, mainly involving red bone marrow.
periapical o. SYN: periapical cemental dysplasia.

osteogen
osteogen (os′te-o-jen)

A bone matrix–producing tissue or layer. [osteo- + G. -gen, producing]

osteogenesis
osteogenesis (os′te-o-jen′e-sis)

The formation of bone. SYN: osteogeny, osteosis (2) , ostosis (2) . [osteo- + G. genesis, production]
distraction o. a technique of inducing new bone formation by dividing a bone and applying tension through an external fixation device to lengthen the bone.
o. imperfecta (OI) a group of connective tissue disorders of type I collagen, characterized by bone fragility, fractures on trivial trauma, skeletal deformity, blue sclerae, ligament laxity, and hearing loss. The Sillence system, which is a clinical, radiographic, and genetic classification, shows four types; inherited as autosomal dominant, caused by mutation in either the collagen type I alpha-1 gene (COL1A1) on chromosome 17q or the alpha-2 gene (COL1A2) on 7q. SYN: brittle bones.
o. imperfecta congenita a severe form [MIM 166230], with fractures occurring before or at birth.
o. imperfecta tarda a less severe form, with fractures occurring later in childhood.
Type I o. imperfecta [MIM*166200] a mild form characterized by blue sclerae, hearing loss, easy bruising, prepubertal bone fragility, and short stature.
Type II o. imperfecta [MIM*166210] a perinatal lethal form associated with stillbirth or lifespan less than 1 year; very fragile connective tissue, and radiographic findings of in utero fractures, large soft cranium, micromelia, tubular long bones, and beaded ribs.
Type III o. imperfecta [MIM*259420] a progressive deforming form with severe bone fragility, easy fractures, triangular facies with relative macrocephaly, skeletal deformities with scoliosis, pectus and bowing of limbs, dwarfism, and radiographic findings of metaphyseal flaring of long bones with sutural bone formation. Most cases are autosomal dominant disorders, but autosomal recessive inheritance has also been described.
Type IV o. imperfecta [MIM*166220] a moderately severe form, characterized by short stature, bone fragility, preambulatory fractures, and bowing of long bones.

osteogenic
osteogenic, osteogenetic (os′te-o-jen′ik, -je-net′ik)

Relating to osteogenesis. SYN: osteogenous, osteoplastic (1) .

osteogenous
osteogenous (os-te-oj′e-nus)

SYN: osteogenic.

osteogeny
osteogeny (os-te-oj′e-ne)

SYN: osteogenesis.

osteography
osteography (os′te-og′ra-fe)

A treatise on or description of the bones. [osteo- + G. graphe, a writing]

osteohalisteresis
osteohalisteresis (os′te-o-hal′is-ter-e′sis)

Softening of the bones through absorption or insufficient supply of the mineral portion. [osteo- + G. hals, salt, + steresis, privation]

osteohypertrophy
osteohypertrophy (os′te-o-hi-per′tro-fe)

Condition characterized by overgrowth of bones. [osteo- + G. hyper- over, + trophe, nourishment]

osteoid
osteoid (os′te-oyd)

1. Relating to or resembling bone. SYN: ossiform. 2. Newly formed organic bone matrix prior to calcification. [osteo- + G. eidos, resemblance]

osteolipochondroma
osteolipochondroma (os′te-o-lip′o-kon-dro′ma)

A benign neoplasm of cartilaginous tissue, in which metaplasia occurs and foci of adipose cells and osseous tissue are formed. [osteo- + G. lipos, fat, + chondros, cartilage, + -oma, tumor]

osteologia
osteologia (os-te-o-lo′je-a)

SYN: osteology, osteology. [L.]

osteologist
osteologist (os′te-ol′o-jist)

A specialist in osteology.

osteology
osteology (os′te-ol′o-je)

The anatomy of the bones; the science concerned with the bones and their structure. SYN: osteologia. [osteo- + G. logos, study]

osteolysis
osteolysis (os-te-ol′i-sis)

Softening, absorption, and destruction of bony tissue, a function of the osteoclasts. [osteo- + G. lysis, dissolution]

osteolytic
osteolytic (os-te-o-lit′ik)

Pertaining to, characterized by, or causing osteolysis.

osteoma
osteoma (os-te-o′ma)

A benign, slow-growing mass of mature, predominantly lamellar bone, usually arising from the skull or mandible. [osteo- + G. -oma, tumor]
o. cutis cutaneous ossification usually secondary to calcification in foci of degeneration in tumors or inflammatory lesions or, rarely, primary new bone formation in normal skin, often associated with Albright hereditary ostrodystrophy.
dental o. an exostosis arising from the root of a tooth.
giant osteoid o. SYN: osteoblastoma.
o. medullare an o. containing spaces that are filled (or partly filled) with various elements of bone marrow.
osteoid o. a painful benign neoplasm that usually originates in one of the bones of the lower extremities, especially the femur or tibia of adolescent and young adult persons; characterized by a nidus (usually no larger than 1 cm in diameter) that consists of osteoid material, vascularized osteogenic stroma, and poorly formed bone; around the nidus there is a relatively large zone of reactive thickening of the cortex.
o. spongiosum an o. that consists chiefly of cancellous bone tissue.

osteomalacia
osteomalacia (os′te-o-ma-la′she-a)

A disease characterized by a gradual softening and bending of the bones with varying severity of pain; softening occurs because the bones contain osteoid tissue that has failed to calcify because of lack of vitamin D or renal tubular dysfunction; more common in women than in men, o. often begins during pregnancy. SYN: adult rickets, late rickets, rachitis tarda. [osteo- + G. malakia, softness]
infantile o., juvenile o. SYN: rickets.
senile o. osteoporosis in the aged.

osteomalacic
osteomalacic (os′te-o-ma-la′sik)

Relating to, or suffering from, osteomalacia.

osteomatoid
osteomatoid (os-te-o′ma-toyd)

An abnormal nodule or small mass of overgrowth of bone, usually occurring bilaterally and symmetrically, in juxtaepiphysial regions, especially in long bones of the lower extremities; lesions are not actually neoplasms, but represent anomalous developments in which there are outpouchings of the cortex (in contrast to a growth superimposed on the cortex), and are more properly termed exostoses. [osteoma + G. eidos, appearance, form]

osteomere
osteomere (os′te-o-mer)

One of the series of bone segments, such as the vertebrae. [osteo- + G. meros, a part]

osteometry
osteometry (os-te-om′e-tre)

The branch of anthropometry concerned with the relative size of the different parts of the skeleton. [osteo- + G. metron, measurement]

osteomyelitis
osteomyelitis (os′te-o-mi-e-li′tis)

Inflammation of the bone marrow and adjacent bone. SYN: central osteitis (1) . [osteo- + G. myelos, marrow, + -itis, inflammation]
chronic diffuse sclerosing o. a proliferative reaction of bone to a low-grade infection of the jaws; most often seen in middle-aged or older black women as extensive, often bilateral radio-opacities of the mandible and maxilla.
chronic focal sclerosing o. a reaction of bone to a mild bacterial infection, often the result of a carious tooth, in persons with a high degree of tissue resistance; results in a localized radio-opacity. SYN: focal condensing osteitis.
Garré o. chronic o. with proliferative periostitis. A focal gross thickening of the periosteum with peripheral reactive bone formation resulting from mild infection.
Pseudomonas o. SYN: malignant external otitis.

osteomyelodysplasia
osteomyelodysplasia (os′te-o-mi′e-lo-dis-pla′-ze-a)

A disease characterized by enlargement of the marrow cavities of the bones, thinning of the osseous tissue, large, thin-walled vascular spaces, leukopenia, and irregular fever. [osteo- + G. myelos, marrow, + dysplasia]

osteon
osteon, osteone (os′te-on, -on)

A central canal containing blood capillaries and the concentric osseous lamellae around it occurring in compact bone. SYN: haversian system. [G. o., bone]

osteoncus
osteoncus (os-te-ong′kus)

An osteoma, sometimes used with reference to any neoplasm of a bone. [osteo- + G. onkos, bulk (swelling)]

osteonecrosis
osteonecrosis (os′te-o-ne-kro′sis)

The death of bone in mass, as distinguished from caries (“molecular death”) or relatively small foci of necrosis in bone. [osteo- + G. nekrosis, death]

osteonectin
osteonectin

A protein (MW 39,000–40,000) found in bone and nonmineralized tissues and believed to play a role in mineralization.

osteopath
osteopath (os′te-o-path)

SYN: osteopathic physician.

osteopathia
osteopathia (os′te-o-path′e-a)

SYN: osteopathy (1) .
o. condensans SYN: osteopoikilosis.
o. hemorrhagica infantum SYN: infantile scurvy.
o. striata linear striations seen radiographically in the metaphyses of long bones and also flat bones; it may be a variant of osteopoikilosis. SYN: Voorhoeve disease.

osteopathic
osteopathic (os-te-o-path′ik)

Relating to osteopathy.

osteopathology
osteopathology (os′te-o-pa-thol′o-je)

Study of diseases of bone.

osteopathy
osteopathy (os-te-op′a-the)

1. Any disease of bone. SYN: osteopathia. 2. A school of medicine based upon a concept of the normal body as a vital machine capable, when in correct adjustment, of making its own remedies against infections and other toxic conditions; practitioners use the diagnostic and therapeutic measures of conventional medicine in addition to manipulative measures. SYN: osteopathic medicine. [osteo- + G. pathos, suffering]
alimentary o. bone disease due to dietary deficiency.

osteopedion
osteopedion (os′te-o-pe′de-on)

Obsolete term for lithopedion. [osteo- + G. paidion, dim. of pais, a child]

osteopenia
osteopenia (os′te-o-pe′ne-a)

1. Decreased calcification or density of bone; a descriptive term applicable to all skeletal systems in which such a condition is noted; carries no implication about causality. 2. Reduced bone mass due to inadequate osteoid synthesis. [osteo- + G. penia, poverty]

osteoperiostitis
osteoperiostitis (os′te-o-per′e-os-ti′tis)

Inflammation of the periosteum and of the underlying bone.

osteopetrosis
osteopetrosis (os′te-o-pe-tro′sis) [MIM*166600]

Excessive formation of dense trabecular bone and calcified cartilage, especially in long bones, leading to obliteration of marrow spaces and to anemia with myeloid metaplasia and hepatosplenomegaly beginning in infancy, to bone fragility, and to progressive deafness and blindness; autosomal dominant inheritance. There are also autosomal recessive forms, which may be mild [MIM*259710], severe [MIM*259700], or lethal [MIM*259720], and sometimes involve a renal tubular defect [MIM*259730]. A milder, autosomal dominant form has onset in childhood and no neurologic sequelae. SYN: Albers-Schönberg disease, marble bone disease, marble bones. [osteo- + G. petra, stone, + -osis, condition]
o. acro-osteolytica SYN: pyknodysostosis.
o. with renal tubular acidosis SYN: carbonic anhydrase II deficiency syndrome.

osteopetrotic
osteopetrotic (os′te-o-pe-trot′ik)

Relating to osteopetrosis.

osteophage
osteophage (os′te-o-faj)

SYN: osteoclast (1) . [osteo- + G. phago, to eat]

osteophlebitis
osteophlebitis (os′te-o-fle-bi′tis)

Inflammation of the veins of a bone. [osteo- + G. phleps, vein, + -itis, inflammation]

osteophony
osteophony (os′te-of′o-ne)

SYN: bone conduction.

osteophyte
osteophyte (os′te-o-fit)

A bony outgrowth or protuberance. [osteo- + G. phyton, plant]

osteoplaque
osteoplaque (os′te-o-plak)

Any osseous layer. [osteo- + Fr. plaque, plate]

osteoplast
osteoplast (os′te-o-plast)

SYN: osteoblast. [osteo- + G. plastos, formed]

osteoplastic
osteoplastic (os-te-o-plas′tik)

1. SYN: osteogenic. 2. Relating to osteoplasty.

osteoplasty
osteoplasty (os′te-o-plas-te)

1. Bone grafting; reparative or plastic surgery of bones. 2. In dentistry, resection of osseous structure to achieve acceptable gingival contour. [osteo- + G. plastos, formed]

osteopoikilosis
osteopoikilosis (os′te-o-poy-ki-lo′sis)

Mottled or spotted bones caused by widespread small foci of compact bone in the substantia spongiosa; autosomal dominant inheritance [MIM*166700]. SEE ALSO: osteopathia striata, dermatofibrosis lenticularis disseminata. SYN: osteopathia condensans. [osteo- + G. poikilos, dappled, + -osis, condition]

osteoponin
osteoponin

A protein produced by osteoblasts of unknown function.

osteopontin
osteopontin

A secreted phosphoprotein, produced by many epithelial cell types, that is highly negatively charged and frequently associated with mineralization processes. It is found in plasma, urine, milk, and bile. Transformed cells express o. in elevated levels. SYN: bone sialoprotein 1.

osteoporosis
osteoporosis (os′te-o-po-ro′sis)

Reduction in the quantity of bone or atrophy of skeletal tissue; an age-related disorder characterized by decreased bone mass and increased susceptibility to fractures. [osteo- + G. poros, pore, + -osis, condition] O. affects 20 million Americans, about 80% of them women, and costs U.S. society as much as $3.8 billion annually. About 1.3 million fractures attributable to o. occur each year in people age 45 and older, and this condition is responsible for 50% of fractures occurring in women over age 50. Although all bones are affected, compression fractures of the vertebrae and traumatic fractures of the wrist and femoral neck are most common. Gradual asymptomatic vertebral compression may be detectable only on radiographic examination. Loss of body height and development of kyphosis may be the only signs of vertebral collapse. After hip fracture, most elderly patients fail to recover normal activity, and mortality within 1 year approaches 20%. Fractures in the elderly often lead to loss of mobility and independence, social alienation, fear of further falls and fractures, and depression. O. occurs when bone resorption outpaces bone formation. Mechanisms underlying o. are complex and probably diverse. Bone constantly undergoes cycles of resorption and formation (remodeling) to maintain the concentration of calcium and phosphate in the extracellular fluid. When serum calcium concentration drops, parathyroid hormone secretion increases, and this hormone stimulates bone resorption by osteoclasts to restore serum calcium levels to normal. Bone mass declines with age and is influenced by sex, race, menopause, and body weight-for-height. Dietary intake of calcium and vitamin D as well as intestinal and renal function affect calcium and phosphate homeostasis. The risk of o. is highest in postmenopausal women. Asian or white race, underweight, dietary calcium deficiency, sedentary lifestyle, alcohol use, and cigarette smoking appear to be independent risk factors. The decline of vitamin D₃ level with aging results in calcium malabsorption, which, in turn, stimulates bone resorption. Estrogen deficiency exacerbates this problem by increasing the sensitivity of bone to resorbing agents. Women who become amenorrheic because of rigorous athletic exercise and dietary restriction or eating disorders are at risk of o.. The formation and resorption of bone are also influenced by external physical factors such as body weight and exercise. Immobilization and prolonged bed rest produce rapid bone loss, while exercise involving weight-bearing has been shown both to reduce bone loss and to increase bone mass. O. is common in young adults with cystic fibrosis, particularly those treated with long-term corticosteroid therapy. The diagnosis of primary o. is established by documentation of reduced bone density after exclusion of known causes of excessive bone loss. Radiographs are insensitive indicators of bone loss, since bone density must be decreased by at least 20–30% before the reduction can be appreciated. Standard diagnostic procedures are determination of bone mineral density at the ultradistal radius and midshaft radius by single-photon absorptiometry, and at the hip and lumbar spine by dual-energy x-ray absorptiometry (DEXA). A quantitative ultrasound procedure recently approved by the FDA is comparable to bone density measurements by DEXA in predicting fractures due to o.. The goal of therapy in o. is prevention of fractures in susceptible patients. The appropriate timing and proper use of agents such as calcium, vitamin D, estrogen, bisphosphonates, calcitonin, and raloxifene and the role of exercise have generated major research efforts and considerable controversy. Intake of adequate amounts of calcium and vitamin D, and continuing moderate weight-bearing exercise, are basic preventive measures for persons of all ages. Administration of estrogen at and after menopause does not simply halt the loss of bone, but actually increases bone mass. Hormone replacement with estrogen remains the most effective prevention and treatment for postmenopausal o.. It is believed to be most appropriate to start estrogen at the earliest sign of the menopause, since bone loss probably begins before the cessation of menses. Estrogen therapy must be continued through later life to maintain optimal bone density. There is no convincing evidence that initiating estrogen therapy in elderly women will prevent o.. The benefits of estrogen therapy must be weighed against the increased risk of endometrial hyperplasia and endometrial carcinoma (which can be offset by concomitant administration of progestogen) and possibly of carcinoma of the breast. The selective estrogen receptor modulator raloxifene has been approved for prevention of o.. It does not cause endometrial hyperplasia but is less effective than estrogen in conserving bone mass. The hormone calcitonin, administered by injection or nasal spray, inhibits bone resorption and has other effects on mineral metabolism. Bisphosphonates such as alendronate and etidronate, which bind to bone crystals, rendering them resistant to enzymatic hydrolysis and inhibiting the action of osteoclasts, have been shown to increase bone mineral density. Strategies to prevent falls are important in elderly patients. see also estrogen replacement therapy, raloxifene.
o. circumscripta cranii localized cranial o. often seen in Paget disease.
juvenile o. idiopathic o. with onset before puberty, leading to pain or fractures, with spontaneous remission within a few years.
posttraumatic o. SYN: Sudeck atrophy.

osteoporotic
osteoporotic (os′te-o-po-rot′ik)

Pertaining to, characterized by, or causing a porous condition of the bones.

osteoprotegerin
osteoprotegerin (os′te-o-pro-teg′er-in)

A secreted protein that inhibits osteoclast differentiation.

osteoradiologist
osteoradiologist (os′te-o-ra-de-ol′o-jist)

A physician who specializes in radiology of the bones and joints. [osteo- + radiologist]

osteoradiology
osteoradiology

The clinical subspecialty of diagnostic bone radiology.

osteoradionecrosis
osteoradionecrosis (os′te-o-ra′de-o-ne-kro′sis)

Necrosis of bone produced by ionizing radiation; may be planned or unplanned. [osteo- + radionecrosis]

osteorrhaphy
osteorrhaphy (os-te-or′a-fe)

Wiring together the fragments of a broken bone. SYN: osteosuture. [osteo- + G. rhaphe, suture]

osteosarcoma
osteosarcoma (os′te-o-sar-ko′ma)

SYN: osteogenic sarcoma.
parosteal o. low-grade o. arising on the surface of bone without involvement of the underlying marrow, usually occurring as a heavily ossified mass of the distal femur in women in the third and fourth decades of life.
periosteal o. chondroblastic o. occurring on the surface of bones without involvement of the marrow; usually presents in adolescents and young adults as a lucent defect with bone spicules extending into soft tissues. Histologically, the tumor is intermediate to high grade, and the cartilage is lobulated.

osteosclerosis
osteosclerosis (os′te-o-skle-ro′sis)

Abnormal hardening or eburnation of bone. [osteo- + G. sklerosis, hardness]

osteosclerotic
osteosclerotic (os′te-o-skle-rot′ik)

Relating to, due to, or marked by hardening of bone substance.

osteosis
osteosis (os-te-o′sis)

1. A morbid process in bone. SYN: ostosis (1) . 2. SYN: osteogenesis. [osteo- + G. -osis, condition]
parathyroid o. SYN: osteitis fibrosa cystica.
renal fibrocystic o. SYN: renal rickets.

osteospongioma
osteospongioma (os′te-o-spon′je-o′ma)

General nonspecific term for a neoplasm in bone that results in thinning and fragmentation (thus, in softening) of the cortex. [osteo- + G. spongos, sponge, + -oma, tumor]

osteosteatoma
osteosteatoma (os′te-o-ste′a-to′ma)

A benign mass, usually a lipoma or sebaceous cyst, in which small foci of bony elements are present. [osteo- + G. stear, suet, fat, + -oma, tumor]

osteosuture
osteosuture (os-te-o-soo′choor)

SYN: osteorrhaphy.

osteosynthesis
osteosynthesis (os-te-o-sin′the-sis)

Internal fixation of a fracture by means of a mechanical device, such as a pin, screw, or plate.

osteothrombosis
osteothrombosis (os′te-o-throm-bo′sis)

Thrombosis in one or more of the veins of a bone.

osteotome
osteotome (os′te-o-tom)

An instrument for use in cutting bone. [osteo- + G. tome, incision]

osteotomy
osteotomy (os-te-ot′o-me)

Cutting a bone, usually by means of a saw or osteotome. [osteo- + G. tome, incision]
“C” sliding o. an extraoral o. in the shape of a “C” performed bilaterally in the mandibular rami for the correction of retrognathia and/or apertognathia.
Dwyer o. a procedure for clubfoot.
horizontal o. an o. performed intraorally for genioplasty; the inferior aspect of the anterior mandible is advanced or retruded by movement of the free segment.
Le Fort o. an o. performed along the classic lines of fracture as described by Le Fort to correct a maxillary skeletal deformity; classified as Le Fort o. I, lower maxillary; II, pyramidal nasoorbitomaxillary; or III, high maxillary, depending upon the location.
sagittal split mandibular o. an intraoral surgical procedure for correction of retrognathism, apertognathia, and prognathism; the mandibular rami and posterior body are sectioned in the sagittal plane.
segmental alveolar o. an intraoral surgical procedure in which segments of alveolar bone containing teeth are sectioned between, and apically to, the teeth for the repositioning of the alveolus and teeth; it may be maxillary or mandibular, and may be combined with ostectomy.
sliding oblique o. an oral surgical procedure in which the mandibular ramus is cut vertically from the sigmoid notch to the angle to facilitate posterior repositioning of the mandible in correction of mandibular prognathism; it may be performed extraorally or intraorally, and is similar to vertical o..
vertical o. an oral surgical procedure similar to sliding oblique o..

osteotribe
osteotribe (os′te-o-trib)

An instrument for crushing off bits of necrosed or carious bone. [osteo- + G. tribo, to bruise, to grind down]

osteotrite
osteotrite (os′te-o-trit)

An instrument with conical or olive-shaped tip having a cutting surface, resembling a dental burr, used for the removal of carious bone. [osteo- + L. tritus, a grinding, a wearing off]

osteotrophy
osteotrophy (os-te-ot′ro-fe)

Nutrition of osseous tissue. [osteo- + G. trophe, nourishment]

osteotympanic
osteotympanic (os′te-o-tim-pan′ik)

SYN: otocranial. [osteo- + G. tympanon, drum]

ostia
ostia (os′te-a)

Plural of ostium. [L.]

ostial
ostial (os′te-al)

Relating to any orifice, or ostium.

ostitic
ostitic (os-ti′tik)

SYN: osteitic.

ostitis
ostitis (os-ti′tis)

SYN: osteitis.

ostium
ostium, pl .ostia (os′te-um, -a) [TA]

A small opening, especially one of entrance into a hollow organ or canal. SEE ALSO: orifice, opening, os, mouth (2) . [L. door, entrance, mouth]
o. abdominale tubae uterinae [TA] SYN: abdominal o. of uterine tube.
abdominal o. of uterine tube [TA] the fimbriated or ovarian extremity of an oviduct. SYN: o. abdominale tubae uterinae [TA] .
o. anatomicum [TA] SYN: anatomical internal os of uterus.
o. aortae [TA] SYN: aortic orifice.
aortic o. SYN: aortic orifice.
o. appendicis vermiformis [TA] SYN: orifice of vermiform appendix.
o. arteriosum SYN: left atrioventricular orifice.
o. atrioventriculare dextrum [TA] SYN: right atrioventricular orifice.
o. atrioventriculare sinistrum [TA] SYN: left atrioventricular orifice.
o. cardiacum [TA] SYN: cardial orifice.
o. histologicum [TA] SYN: histological internal os of uterus.
o. ileale [TA] SYN: ileal orifice.
o. ileocecale SYN: ileal orifice.
o. internum SYN: uterine o. of uterine tubes.
o. pharyngeum tubae auditivae [TA] SYN: pharyngeal opening of pharyngotympanic (auditory) tube.
o. pharyngeum tubae auditoriae pharyngeal opening of pharyngotympanic (auditory) tube.
o. primum SYN: interatrial foramen primum.
o. pyloricum [TA] SYN: pyloric orifice.
o. secundum SYN: interatrial foramen secundum.
o. sinus coronarii [TA] SYN: opening of coronary sinus.
o. trunci pulmonalis [TA] SYN: opening of pulmonary trunk.
o. tympanicum tubae auditivae [TA] SYN: tympanic opening of pharyngotympanic (auditory) tube.
o. ureteris [TA] SYN: ureteric orifice.
o. urethrae externum [TA] SYN: external urethral orifice.
o. urethrae internum [TA] SYN: internal urethral orifice.
o. urethrae internum evacuans [TA] SYN: voiding internal urethral orifice.
o. uteri [TA] SYN: external os of uterus.
o. uteri externum SYN: external os of uterus.
o. uteri internum SYN: isthmus of uterus.
uterine o. of uterine tubes [TA] the uterine opening of the oviduct. SYN: o. uterinum tubae uterinae [TA] , o. internum, uterine opening of uterine tubes.
o. uterinum tubae uterinae [TA] SYN: uterine o. of uterine tubes.
o. vaginae [TA] SYN: vaginal orifice.
o. venae cavae inferioris [TA] SYN: opening of inferior vena cava.
o. venae cavae superioris [TA] SYN: opening of superior vena cava.
ostia venarum pulmonalium [TA] SYN: openings of pulmonary veins, under opening.
o. venosum cordis SYN: right atrioventricular orifice.
o. of vermiform appendix SYN: orifice of vermiform appendix.

ostomate
ostomate (os′to-mat)

Term for one who has an ostomy. [L. ostium, mouth]

ostomy
ostomy (os′to-me)

1. An artificial stoma or opening into the urinary or gastrointestinal canal, or the trachea. 2. Any operation by which a permanent opening is created between two hollow organs or between a hollow viscus and the skin externally, as in tracheostomy. [L. ostium, mouth]

-ostomy -ostomy

See -stomy.

ostosis
ostosis (os-to′sis)

1. SYN: osteosis (1) . 2. SYN: osteogenesis.

ostraceous
ostraceous (os-tra′shus)

Denoting the heaping up of scales seen in psoriasis, which resembles the stratification of oyster shells. [Ostraeacea, group including the oysters]

ostreotoxism
ostreotoxism (os′tre-o-tok′sizm)

Poisoning from eating infected or contaminated oysters. [G. ostreon, oyster, + toxikon, poison]

Ostwald
Ostwald

Friedrich Wilhelm, German physical chemist and Nobel laureate, 1853–1932. See O. solubility coefficient.

OT
OT

Abbreviation for occupational therapist or therapy; Koch old tuberculin.

ot- ot-

The ear. SEE ALSO: auri-. [G. ous]

Ota
Ota

Masao T., Japanese dermatopathologist, 1885–1945. See O. nevus.

otalgia
otalgia (o-tal′je-a)

SYN: earache. [ot- + G. algos, pain]
geniculate o. SYN: geniculate neuralgia.
reflex o. pain referred to the ear from disease in another part, most commonly teeth, maxillary sinus, nasopharynx, tonsil, pharynx, or larynx.

otalgic
otalgic (o-tal′jik)

1. Relating to otalgia, or earache. 2. A remedy for earache.

OTC
OTC

Abbreviation for over the counter, pertaining to a drug available without a prescription.

other-directed
other-directed (odh′er-di-rek′ted)

Pertaining to a person readily influenced by the attitudes of others.

otic
otic (o′tik)

Relating to the ear. [G. otikos, fr. ous, ear]

Otis
Otis

Arthur Brooks, U.S. respiratory physiologist, *1913. See Rahn-O. sample.

otitic
otitic (o-tit′ik)

Relating to otitis.

otitis
otitis (o-ti′tis)

Inflammation of the ear. [ot- + G. -itis, inflammation]
adhesive o. inflammation of the middle ear caused by prolonged eustachian tube dysfunction resulting in permanent retraction of the eardrum and obliteration of the middle ear space.
o. desquamativa o. externa with a copious desquamation.
o. externa inflammation of the external auditory canal. SYN: swimmer's ear.
o. interna SYN: labyrinthitis.
malignant external o. a life-threatening Pseudomonas osteomyelitis of the temporal bone in elderly diabetics that begins with ear pain and swelling of and discharge from the external auditory canal. SYN: Pseudomonas osteomyelitis.
o. media inflammation of the middle ear, or tympanum.
reflux o. media o. media caused by passage of an ingested liquid (usually milk) or nasopharyngeal secretions through the eustachian tube.
secretory o. media SYN: middle-ear effusion.
serous o. media SYN: middle-ear effusion.

oto- oto-

The ear. SEE ALSO: auri-. [G. ous]

otoacoustic
otoacoustic (o′to-a-koo-stik)

Referring to the very faint sounds produced by the ear; thought to represent mechanical vibrations in the cochlea.

otobiosis
otobiosis (o′to-bi-o′sis)

Presence of larvae and the characteristic spiny nymphs of the tick Otobius megnini in the external auditory canal of cattle, horses, cats, dogs, deer, coyotes, and other domestic and wild animals; they may remain in the ear for several months before dropping out to pupate and mature. Several records of human infestation are known.

Otobius
Otobius (o-to′be-us)

A genus of argasid ticks similar to Ornithodoros but characterized by a granulated integument, a hypostome that is vestigial in the adult but well developed in the spiny nymphs, and the absence of eyes and hood. Two species are recognized: O. lagophilus (the face tick of rabbits) and O. megnini, the spinose ear tick that causes otobiosis in horses, cattle, sheep, dogs, and some wild animals; it occurs in southwestern parts of the U.S., where it is an important pest, and is also distributed worldwide.

otocephaly
otocephaly (o-to-sef′a-le)

Malformation characterized by markedly defective development of the lower jaw (micrognathia or agnathia) and the union or close approach of the ears (synotia) on the front of the neck. [oto- + G. kephale, head]

otocerebritis
otocerebritis (o-to-ser-e-bri′tis)

SYN: otoencephalitis.

otoconia
otoconia, gen. otoconium (o-to-ko′ne-a, -um)

SYN: otoliths.

otocranial
otocranial (o-to-kra′ne-al)

Relating to the otocranium. SYN: osteotympanic.

otocranium
otocranium (o′to-kra′ne-um)

The bony case of the internal and middle ear, consisting of the petrous portion of the temporal bone. [oto- + G. kranion, cranium]

otocyst
otocyst (o′to-sist)

1. Embryonic auditory vesicle. 2. A balancing organ, analogous to the utricle of mammals, possessed by certain invertebrates and containing grains of calcareous material or of sand. [oto- + G. kystis, a bladder]

Otodectes
Otodectes (o-to-dek′tez)

A genus of ear mites (family Psoroptidae) consisting of a single species, O. cynotis, the cause of otodectic mange in dogs, cats, and other carnivores; the entire lifespan of this mite is spent in the ears (rarely on the body) of the host, where it feeds on epidermal debris; it can be found in the encrusted material scraped from infected ears. [oto- + dektes, beggar, receiver]

otodectic
otodectic (o-to-dek′tik)

Of, relating to, or caused by mites of the genus Otodectes.

otodynia
otodynia (o-to-din′e-a)

SYN: earache. [oto- + G. odyne, pain]

otoencephalitis
otoencephalitis (o′to-en-sef-a-li′tis)

Inflammation of the brain by extension of the process from the middle ear and mastoid cells. SYN: otocerebritis. [oto- + G. enkephalos, brain, + -itis, inflammation]

otoganglion
otoganglion (o′to-gang′gle-on)

SYN: otic ganglion.

otogenic
otogenic, otogenous (o′to-jen′ik, o-toj′e-nus)

Of otic origin; originating within the ear, especially from inflammation of the ear. [oto- + G. -gen, producing]

otolaryngologist
otolaryngologist (o′to-lar-ing-gol′o-jist)

A physician who specializes in otolaryngology.

otolaryngology
otolaryngology (o′to-lar-ing-gol′o-je)

The combined specialties of diseases of the ear and larynx, including the upper respiratory tract and diseases of the head and neck, tracheobronchial tree, and esophagus. [oto- + G. larynx, + logos, study]

otoliths
otoliths, otolites (o′to-lith, o′to-lit) [TA]

Crystalline particles of calcium carbonate and a protein adhering to the gelatinous membrane of the maculae of the utricle and saccule. SYN: statoconia [TA] , ear crystals, otoconia, sagitta, statoliths. [oto- + G. lithos, stone]

otologic
otologic (o′to-loj′ik)

Relating to otology.

otologist
otologist (o-tol′o-jist)

A specialist in otology.

otology
otology (o-tol′o-je)

The branch of medical science concerned with the study, diagnosis, and treatment of diseases of the ear and related structures. [oto- + G. logos, study]

otomucormycosis
otomucormycosis (o-to-mu′kor-mi-ko′sis)

Mucormycosis of the ear.

-otomy -otomy

See -tomy.

otomycosis
otomycosis (o′to-mi-ko′sis)

An infection in which fungal mycelia are seen in cerumen and desquamated cells in the external auditory canal, usually unilateral, with scaling, itching, and pain as the primary symptoms. The fungus does not invade tissue and plays little role in pathogenicity.

otoneuralgia
otoneuralgia (o′to-noo-ral′je-a)

Earache of neuralgic origin, not caused by inflammation. [oto- + G. neuron, nerve, + algos, pain]

otopalatodigital
otopalatodigital (o′to-pal′a-to-dij′i-tal)

Relating to the ears, palate, and fingers.

otopathy
otopathy (o-top′a-the)

Any disease of the ear. [oto- + G. pathos, suffering]

otopharyngeal
otopharyngeal (o′to-fa-rin′je-al)

Relating to the middle ear and the pharynx.

otoplasty
otoplasty (o′to-plas-te)

Constructive or reparative plastic surgery of the ear. [oto- + G. plastos, formed]

otorhinolaryngology
otorhinolaryngology (o′to-ri′no-lar-ing -gol′o-je)

The combined specialties of diseases of the ear, nose, pharynx, and larynx; including diseases of the head and neck, tracheobronchial tree, and esophagus. SEE ALSO: otolaryngology. [oto- + G. rhis, nose, + larynx, larynx, + logos, study]

otorrhea
otorrhea (o-to-re′a)

A discharge from the ear. [oto- + G. rhoia, flow]
cerebrospinal fluid o. discharge of cerebrospinal fluid through the external auditory meatus or through the eustachian tube into the nasopharynx.

otosalpinx
otosalpinx (o-to-sal′pingks)

SYN: pharyngotympanic (auditory) tube. [oto- + G. salpinx, trumpet]

otosclerosis
otosclerosis (o′to-skle-ro′sis)

A disease of the otic capsule (bony labyrinth) characterized by formation of soft, vascular bone and resulting in progressive conductive hearing loss because of fixation of the stapes and sensory hearing loss because of involvement of the cochlear duct. [oto- + G. sklerosis, hardening]

otoscope
otoscope (o′to-skop)

An instrument for examining the eardrum. [oto- + G. skopeo, to view]
Siegle o. an otosclerosis with a bulb attachment by which the air pressure can be varied, thus imparting movement to the tympanic membrane, if intact, while under inspection.

otoscopy
otoscopy (o-tos′ko-pe)

Inspection of the ear, especially of the eardrum. [oto- + G. skopeo, to view]
pneumatic o. inspection of the ear with a device capable of varying air pressure against the eardrum. Imparting movement to the tympanic membrane suggests normal middle ear compliance; the lack of movement indicates either increased impedance, as with fluid in the middle ear, or perforation of the tympanic membrane.

otospongiosis
otospongiosis (ot-o-spun-je-o′sis)

A more accurately descriptive term for the pathologic changes in otosclerosis.

otosteal
otosteal (o-tos′te-al)

Relating to the ossicles of the ear. [oto- + G. osteon, bone]

ototoxic
ototoxic (o′to-tok′sik)

Relating to ototoxicity.

ototoxicity
ototoxicity (o-to-tok-sis′i-te)

The property of being injurious to the ear. [oto- + G. toxikon, poison]
familial aminoglycoside o. inherited susceptibility to sensory hearing loss upon administration of aminoglycoside antibiotics due to a mutation in the mitochondrial genome.

Otto
Otto

Adolph W., German surgeon, 1786–1845. See O. pelvis, O. disease.

otto of rose
otto of rose

SYN: oil of rose.

Ottoson
Ottoson

David, Swedish physiologist, *1918. See O. potential.

O.U.
O.U.

Abbreviation for Latin oculus uterque, each eye or both eyes.

ouabagenin
ouabagenin (wa′ba-jen-in)

The aglycon obtained from the hydrolysis of the cardiac glycoside, ouabain; exerts cardiotonic activity.

ouabain
ouabain (wah′ban, wah′bah-in)

A glycoside and African arrow poison from ouabaio, obtained from the wood of Acocanthera ouabaio or from the seeds of Strophanthus gratus; its action is qualitatively identical to that of strophanthus and the digitalis glycosides; used for rapid digitalization; often used in pharmacological studies because of water solubility.

Ouchterlony
Ouchterlony

Orjan, Swedish bacteriologist, *1914. See O. method, O. technique, O. test, O. technique.

oul- oul-

For words beginning thus, see ulo-.

ounce
ounce (oz.) (owns)

A weight containing 480 g, or 112 pound troy and apothecaries' weight, or 437.5 g, 116 pound avoirdupois. The apothecary oz (used in the USP) contains 8 dram and is equivalent to 31.10349 g; the avoirdupois oz is equivalent to 28.35 g. [L. uncia, the twelfth part (of a pound or foot) hence also inch]

-ous -ous

1. Chemical suffix attached to the name of an element in one of its lower valencies. Cf.:-ic (1) . 2. Having much of. [L. -osus, full of, abounding]

outlet
outlet (owt′let) [TA]

An exit or opening of a passageway. SEE ALSO: aperture.
pelvic o. [TA] the lower opening of the true pelvis, bounded anteriorly by the pubic arch, laterally by the rami of the ischium and the sacrotuberous ligament on either side, and posteriorly by these ligaments and the tip of the coccyx. SYN: apertura pelvis inferior [TA] , apertura pelvis minoris, fourth parallel pelvic plane, inferior pelvic aperture, pelvic plane of o., plane of o..
thoracic o. 1. SYN: inferior thoracic aperture. 2. SYN: superior thoracic aperture.

outlier
outlier (owt′le-er)

An observation that differs so widely from all others in a set as to justify the conclusion that a gross error has occurred or that it comes from a different population.

outpatient
outpatient (owt′pa′shent)

A patient treated in a hospital dispensary or clinic instead of in an overnight room or ward.

out of phase
out of phase

Not in phase, moving in opposite directions at the same time; 180° o.; a possible characteristic of two simultaneous oscillations of similar frequency.

output
output (owt′poot)

The quantity produced, ejected, or excreted of a specific entity in a specified period of time or per unit time, e.g., urinary sodium o.; the opposite of intake or input.
cardiac o. the amount of blood ejected by the heart in a unit of time ( i.e., the minute volume), usually expressed in liters per minute. SYN: minute o..
maximum power o. the greatest sound resulting from amplification that the instrument can produce; an indication of hearing aid performance.
minute o. SYN: cardiac o..
pacemaker o. electrical energy delivered into a standard load (500 Ω resistance).
stroke o. SYN: stroke volume.

ova
ova (o′va)

Plural of ovum. [L.]

oval
oval (o′val)

1. Relating to an ovum. 2. Egg-shaped, resembling in outline the longitudinal section of an egg.

ovalbumin
ovalbumin (o-val-bu′min)

The chief protein occurring in the white of egg and resembling serum albumin; also found in phosphorylated form. SYN: albumen, egg albumin.

ovalocytosis
ovalocytosis (o′va-lo-si-to′sis)

SYN: elliptocytosis.

ovarialgia
ovarialgia (o-var-e-al′je-a)

Pain in an ovary. SYN: oophoralgia. [ovario- + G. algos, pain]

ovarian
ovarian (o-var′e-an)

Relating to the ovary.

ovariectomy
ovariectomy (o-var-e-ek′to-me)

Excision of one or both ovaries. SYN: oophorectomy. [ovario- + G. ektome, excision]

ovario- ovario-, ovari-

Ovary. SEE ALSO: oo-, oophor-. [L. ovarium]

ovariocele
ovariocele (o-var′e-o-sel)

Hernia of an ovary. [ovario- + G. kele, hernia]

ovariocentesis
ovariocentesis (o-var′e-o-sen-te′sis)

Puncture of an ovary or an ovarian cyst. [ovario- + G. kentesis, puncture]

ovariocyesis
ovariocyesis (o-var′e-o-si-e′sis)

SYN: ovarian pregnancy. [ovario- + G. kyesis, pregnancy]

ovariodysneuria
ovariodysneuria (o-var′e-o-dis-noo′re-a)

Ovarian pain or neuralgia. [ovario- + G. dys-, bad, + neuron, nerve]

ovariogenic
ovariogenic (o-var′e-o-jen′ik)

Originating in the ovary. [ovario- + G. -gen, producing]

ovariolytic
ovariolytic (o-var′e-o-lit′ik)

Destructive to the ovary. [ovario- + G. lysis, dissolution]

ovariopathy
ovariopathy (o-var-e-op′a-the)

Any disease of the ovary. SYN: oophoropathy. [ovario- + G. pathos, suffering]

ovariorrhexis
ovariorrhexis (o-var′e-o-rek′sis)

Rupture of an ovary. [ovario- + G. rhexis, rupture]

ovariosalpingectomy
ovariosalpingectomy (o-var′e-o-sal-pin-jek′to-me)

Operative removal of an ovary and the corresponding oviduct. SYN: oophorosalpingectomy. [ovario- + salpingectomy]

ovariosalpingitis
ovariosalpingitis (o-var′e-o-sal-pin-ji′tis)

Inflammation of ovary and oviduct. SYN: oophorosalpingitis. [ovario- + salpingitis]

ovariostomy
ovariostomy (o-var-e-os′to-me)

Establishment of a temporary fistula for drainage of a cyst of the ovary. [ovario- + G. stoma, mouth]

ovariotomy
ovariotomy (o-var-e-ot′o-me)

An incision into an ovary, e.g., a biopsy or a wedge excision. SYN: oophorotomy. [ovario- + G. tome, incision]

ovaritis
ovaritis (o-va-ri′tis)

SYN: oophoritis.

ovarium
ovarium, pl .ovaria (o-var′e-um, -a) [TA]

SYN: ovary. [Mod. L. fr. ovum, egg]
o. bipartitum an ovary separated into two distinct parts.
o. disjunctum an ovary partially or completely divided into two sections.
o. gyratum an ovary showing curved or irregular grooves or furrows.
o. lobatum an ovary demarcated by deep furrows into two or more lobes.
o. masculinum SYN: appendix of testis.

ovary
ovary (o′va-re) [TA]

One of the paired female reproductive glands containing the ova or germ cells; the ovaries stroma is a vascular connective tissue containing numbers of ovarian follicles enclosing the ova; surrounding this stroma is a more condensed layer of stroma called the tunica albuginea. SYN: ovarium [TA] , female gonad, genital gland (2) . [Mod. L. ovarium, fr. ovum, egg]
mulberry o. the type of o. produced by the administration of anterior pituitary extracts to immature rats; such an o. contains many more follicles than normal, with the follicles in various stages of development and with prominent corpora lutea on their surfaces, thus the perceived resemblance to a mulberry.
polycystic o. enlarged cystic ovaries, pearl white in color, with thickened tunica albuginea, characteristic of the Stein-Leventhal syndrome; clinical features are abnormal menses, obesity, and evidence of masculinization, such as hirsutism.
third o. an accessory o..

overbite
overbite (o′ver-bit)

SYN: vertical overlap.

overclosure
overclosure (o′ver-klo-zher)

A decrease in occlusal vertical dimension.

overcompensation
overcompensation (o′ver-kom-pen-sa′shun)

1. An exaggeration of personal capacity by which one overcomes a real or imagined inferiority. 2. The process in which a psychologic deficiency inspires exaggerated correction. See compensation.

overcorrection
overcorrection (o′ver-ko-rek′shun)

In behavior modification treatment programs, especially those involving mentally retarded individuals, overlearning the desired target behavior beyond the set criterion to assure that the behavior will continue to meet the established criterion when the post-learning decrements and forgetting occur.

overdenture
overdenture (o-ver-den′choor)

SYN: overlay denture.

overdetermination
overdetermination (o′ver-de-ter′min-a′shun)

In psychoanalysis, ascribing the cause of a single behavioral or emotional reaction, mental symptom, or dream to the operation of two or more forces, that is, it is overdetermined ( e.g., ascribing the nature of an emotional outburst not only to the immediate precipitant but also to a lingering inferiority complex).

overdominance
overdominance (o-ver-dom′i-nans)

That state in which the heterozygote has greater phenotype value and perhaps is more fit than the homozygous state for either of the alleles that it comprises. Cf.:balanced polymorphism.

overdominant
overdominant (o-ver-dom′i-nant)

Denoting heterozygous states that exhibit overdominance.

overdrive
overdrive (o-ver-driv)

1. An electrophysiologic pacing technique to exceed the rate of an abnormal pacemaker and so capture the territory controlled by that pacemaker (usually atrial). 2. A state of eukaryotic RNA polymerase wherein it is resistant to pause, arrest, or termination signals. SEE ALSO: hesitant, antitermination.

overeruption
overeruption (o′ver-e-rup′shun)

Occlusal projection of a tooth beyond the line of occlusion.

overextension
overextension (o-ver-eks-ten′shun)

SYN: hyperextension.

overgrafting
overgrafting (o′ver-graft′ing)

Placing a second or additional grafts over a previously healed graft from which the epithelium has been removed, as with dermabrasion, to strengthen and thicken a split-thickness graft.

overhang
overhang (o′ver-hang)

An excess of dental filling material beyond the cavity margin or normal tooth contour.

overhead projector
overhead projector

SYN: epidiascope.

overhydration
overhydration (o′ver-hi-dra′shun)

SYN: hyperhydration.

overjet
overjet, overjut (o′ver-jet, o′ver-jut)

SYN: horizontal overlap.

overlap
overlap (o′ver-lap)

1. Suturing of one layer of tissue above or under another to gain strength. 2. An extension or projection of one tissue over another.
horizontal o. the projection of the upper anterior and/or posterior teeth beyond their antagonists in a horizontal direction. SYN: overjet, overjut.
vertical o. 1. the extension of the upper teeth over the lower teeth in a vertical direction when the opposing posterior teeth are in contact in centric occlusion; 2. the distance that teeth lap over their antagonists vertically, especially for the distance that the upper incisal edges drop below the lower ones, but may also describe the vertical relations of opposing cusps; 3. the relationship of the maxillary incisors to the mandibular incisors when the incisal edges pass each other in centric occlusion. SYN: overbite.

overlay
overlay (o′ver-la)

An addition to an already existing condition.
emotional o. the emotional or psychologic concomitant of an organic disability.

overlearning
overlearning (o′ver-lern′ing)

In the psychology of memory, continuation of practice beyond the point at which one is able to perform according to the specified criterion; typically, retention is longer after o. as compared with retention after practice only to the point of performance meeting the specified criterion.

overresponse
overresponse (o′ver-re-spons′)

An abnormally strong reaction to a stimulus.

overriding
overriding (o′ver-ri′ding)

1. Slippage of the lower fragment of a broken long bone upward and alongside the proximal portion. 2. Obsolete term denoting a fetal head that is palpable above the symphysis because of cephalopelvic disproportion. 3. The slippage of fetal bones of the skull that occurs after an interutero fetal death.

oversensing
oversensing (o′ver-sen′sing)

Sensing of electrical or magnetic signals, which normally should not be sensed by a pacemaker, but result in inappropriate inhibition of the pacemaker's output.

overshoot
overshoot (o′ver-shoot)

1. Generally, any initial change, in response to a sudden step change in some factor, that is greater than the steady-state response to the new level of that factor; common in systems in which inertia or a time lag in negative feedback outweighs any damping that may be present. Changes in a negative direction are sometimes distinguished by the term undershoot, and the two may alternate in an oscillatory fashion, as in the transient oscillations of a pendulum when released from an initial displacement. 2. Momentary reversal of the membrane potential of a cell (inside becoming positive rather than negative relative to the outside) during an action potential; considered a form of o. (1) because, before discovery of o. (2) , excitation was thought merely to depolarize the membrane to zero transmembrane potential.

Overton
Overton

Charles E., German biologist in Sweden, 1865–1933. See Meyer-O. rule, Meyer-O. theory of narcosis.

overtone
overtone (o′ver-ton)

Any of the tones, other than the lowest or fundamental tone, of which a complex sound is composed.
psychic o. the mental associations related to any stimulus.

overventilation
overventilation (o′ver-ven-ti-la′shun)

SYN: hyperventilation.

overwintering
overwintering (o′ver-win′ter-ing)

Persistence of an infectious agent in its vector for extended periods, such as the cooler winter months, during which the vector has no opportunity to be reinfected or to infect another host.

ovi- ovi-

Egg. SEE ALSO: oo-, ovo-. [L. ovum]

ovicidal
ovicidal (o-vi-si′dal)

Causing death of the ovum. [ovi- + L. caedo, to kill]

oviducal
oviducal (o-vi-doo′kal)

SYN: oviductal.

oviduct
oviduct (o′vi-dukt)

SYN: uterine tube. [ovi- + L. ductus, a leading, fr. duco, pp. ductus, to lead]

oviductal
oviductal (o-vi-duk′tal)

Relating to a uterine tube. SYN: oviducal.

oviferous
oviferous (o-vif′er-us)

Carrying, containing, or producing ova. SYN: ovigerous. [ovi- + L. fero, to carry]

oviform
oviform (o′vi-form)

SYN: ovoid (2) .

ovigenesis
ovigenesis (o-vi-jen′e-sis)

SYN: oogenesis.

ovigenetic
ovigenetic, ovigenic (o-vi-je-net′ik, -jen′ik)

SYN: oogenetic.

ovigenous
ovigenous (o-vij′e-nus)

SYN: oogenetic.

ovigerous
ovigerous (o-vij′er-us)

SYN: oviferous.

ovigerus
ovigerus

SYN: cumulus oöphorus.

ovine
ovine (o′vin)

Relating to sheep; sheeplike. [L. ovinus, relating to a sheep]

oviparity
oviparity (o-vi-par′i-te)

The quality of being oviparous. [ovi- + L. pario, to bear]

oviparous
oviparous (o-vip′a-rus)

Egg-laying; denoting those birds, fish, amphibians, reptiles, monotreme mammals, and invertebrates whose young develop in eggs outside of the maternal body. [L. oviparus, fr. ovum, egg, + pario, to bear]

oviposit
oviposit (o′vi-poz′it)

To lay eggs; applied especially to insects. [ovi- + L. pono, pp. positus, to place]

oviposition
oviposition (o′vi-po-zish′un)

Act of laying or depositing eggs by insects.

ovipositor
ovipositor (o-vi-poz′i-tor, -tor)

A specialized female organ especially well developed in insects for laying or depositing eggs.

ovist ovist (o′vist)

A preformationist who believed that the female sex cell contained a miniature body susceptible to growth when stimulated by semen. Cf.:spermist.

ovo- ovo-

Egg. SEE ALSO: oo-, ovi-. [L. ovum]

ovocyte
ovocyte (o′vo-sit)

SYN: oocyte. [ovo- + G. kytos, a hollow (cell)]

ovoflavin
ovoflavin (o-vo-fla′vin)

Riboflavin found in eggs.

ovogenesis
ovogenesis (o-vo-jen′e-sis)

SYN: oogenesis.

ovoglobulin
ovoglobulin (o-vo-glob′u-lin)

Globulin in the white of egg.

ovoid
ovoid (o′voyd)

1. An oval or egg-shaped form. 2. Resembling an egg. SYN: oviform. [ovo- + G. eidos, resemblance]
fetal o. the form of the fetus in utero; its length is about one-half of the length of the extended fetus.
Manchester o. an egg-shaped radium applicator for placement in the lateral vaginal fornices. [University of Manchester, England]

ovolarviparous
ovolarviparous (o′vo-lar-vip′a-rus)

Denoting certain nematodes and other invertebrates in which the eggs are hatched within the female, and the larvae developed or protected within the uterus until the correct time for their emergence. [ovo- + L. larva, a mask, + pario, to bear]

ovomucin
ovomucin (o-vo-mu′sin)

A glycoprotein in the white of egg.

ovomucoid
ovomucoid (o-vo-mu′koyd)

A mucoprotein obtained from the white of egg.

ovoplasm
ovoplasm (o′vo-plazm)

Protoplasm of an unfertilized egg.

ovoprotogen
ovoprotogen (o-vo-pro′to-jen)

SYN: lipoic acid.

ovosiston
ovosiston (o-vo-sis′ton)

An oral contraceptive that consists of a mixture of a progestin and an estrogen.

ovotestis
ovotestis (o′vo-tes′tis)

Gonad in which both testicular and ovarian components are present; a form of hermaphroditism.

ovotransferrin
ovotransferrin (o′vo-trans-far′in)

SYN: conalbumin.

ovovitellin
ovovitellin (o′vo-vi-tel′in)

SYN: vitellin. [ovo- + L. vitellus, yolk]

ovoviviparous
ovoviviparous (o′vo-vi-vip′a-rus)

Denoting those fish, amphibians, and reptiles that produce eggs that hatch within the body of the parent. [ovo- + L. viviparus, bringing forth alive, fr. vivus, alive, + pario, to bear]

ovular
ovular (ov′u-lar, o′vu-)

Relating to an ovule.

ovulation
ovulation (ov′u-la′shun, o′vu-)

Release of an ovum from the ovarian follicle.
anestrous o. discharge of ova occurring in animals without estrus.
paracyclic o. obsolete term for o. occurring in the menstrual cycle at any time other than the normally anticipated time.

ovulatory
ovulatory (ov′u-la-to-re, o′vu-)

Relating to ovulation.

ovule
ovule (ov′ul, o′vu-)

1. The ovum of a mammal, especially while still in the ovarian follicle. 2. A small beadlike structure bearing a fancied resemblance to an o.. SYN: ovulum. [Mod. L. ovulum, dim. of L. ovum, egg]

ovulocyclic
ovulocyclic (ov′u-lo-si′klik, o′vu-)

Denoting any recurrent phenomenon associated with and occurring at a certain time within the ovulatory cycle, as, for example, o. porphyria.

ovulum
ovulum, pl .ovula (ov′u-lum, o′vu-; -la)

SYN: ovule.

ovum
ovum, gen. ovi, pl .ova (o′vum, -vi, -va)

The female sex cell. When fertilized by a spermatozoon, an o. is capable of developing into a new individual of the same species; during maturation, the o., like the spermatozoon, undergoes a halving of its chromosomal complement so that, at its union with the male gamete, the species number of chromosomes (46 in humans) is maintained; yolk contained in the ova of different species varies greatly in amount and distribution, which influences the pattern of the cleavage divisions. [L. egg]
alecithal o. an o. in which the yolk is nearly absent, consisting of only a few particles.
blighted o. a fertilized o. whose development has ceased at an early stage.
centrolecithal o. one in which the yolk is mostly located near the center of the egg, as in arthropods.
fertilized o. an o. impregnated by a spermatozoon.
isolecithal o. an o. in which the yolk is evenly distributed throughout the cytoplasm.
Peters o. an o. with a presumptive fertilization age of about 13 days; for many years, it was one of very few young human embryos recovered in good condition and its study furnished many facts regarding early embryonic changes.
telolecithal o. an o. in which there is a large amount of yolk massed at the vegetative pole, as in the eggs of birds and reptiles.

Owen
Owen

Sir Richard, English anatomist, 1804–1892. See O. lines, under line, contour lines of O., under line, interglobular space of O..

Owren
Owren

Paul A., Norwegian hematologist, *1905. See O. disease.

oxa- oxa-

Combining form inserted in names of organic compounds to signify the presence or addition of oxygen atom(s) in a chain or ring (as in ethers), not appended to either (as in ketones and aldehydes). SEE ALSO: hydroxy-, oxo-, oxy-. [English. oxygen]

oxacillin sodium
oxacillin sodium (ok-sa-sil′in)

A semisynthetic penicillin used in the oral therapy of penicillin-resistant staphylococcal infections.

oxalaldehyde
oxalaldehyde (ok-sa-lal′de-hid)

SYN: glyoxal.

oxalate
oxalate (ok′sa-lat)

A salt of oxalic acid.

oxalemia
oxalemia (ok-sa-le′me-a)

The presence of an abnormally large amount of oxalates in the blood. [oxalate + G. haima, blood]

oxalic acid
oxalic acid (ok-sal′ik)

An acid, HOOC–COOH, found in many plants and vegetables, particularly in buckwheat (family Polygoniaceae) and Oxalis (family Oxalidaceae); used as a hemostatic in veterinary medicine, but toxic in elevated levels when ingested by humans; also used in the removal of ink and other stains, and as a general reducing agent; salts of o. are found in renal calculi; accumulates in cases of primary hyperoxaluria.

oxalo
oxalo (ok′sa-lo)

The monoacyl radical, HOOC–C(O)–.

oxaloacetate transacetase
oxaloacetate transacetase (ok′sa-lo-as′e-tat trans-as′e-tas)

SYN: citrate synthase.

oxaloacetic acid
oxaloacetic acid (ok′sa-lo-a-se′tik)

A ketodicarboxylic acid and important intermediate in the tricarboxylic acid cycle; the product formed when l-aspartic acid acts as an amine donor in transamination reactions. SYN: ketosuccinic acid, oxosuccinic acid.

oxalosis
oxalosis (ok-sa-lo′sis)

Widespread deposition of calcium oxalate crystals in the kidneys, bones, arterial media, and myocardium, with increased urinary excretion of oxalate; may be an acquired disorder, as in oxalate poisoning, or represent one aspect of primary hyperoxaluria and o.. [oxalate + -osis, condition]

oxalosuccinic acid
oxalosuccinic acid (ok′sa-lo-suk-sin′ik)

The product of the dehydrogenation of isocitric acid under the catalytic influence of isocitrate dehydrogenase; an enzyme-bound intermediate of the tricarboxylic acid cycle.

oxalosuccinic carboxylase
oxalosuccinic carboxylase

SYN: isocitrate dehydrogenase.

oxalourea
oxalourea (ok′sa-lo-u-re′a)

SYN: oxalylurea.

oxaluria
oxaluria (ok-sa-loo′re-a)

SYN: hyperoxaluria. [oxalate + G. ouron, urine]

oxaluric acid
oxaluric acid (ok-sa-loor′ik)

The ureide of oxalic acid, derived from uric acid or oxalylurea.

oxalyl
oxalyl (ok′sa-lil)

The diacyl radical, –CO–CO– .

oxalylurea
oxalylurea (ok′sa-lil-u-re′a)

The cyclic (end-to-end) amide anhydride of oxaluric acid; an oxidation product of uric acid. SYN: oxalourea, parabanic acid.

oxamniquine
oxamniquine (oks-am′ni-quin)

A tetrahydroquinoline derivative, similar to hycanthone and lucanthone, effective against Schistosoma mansoni; now largely superseded by the broad-spectrum anthelmintic drug praziquantel.

oxanamide
oxanamide (ok-san′a-mid)

A sedative.

oxandrolone
oxandrolone (ok-san′dro-lon)

17β-Hydroxy-17α-methyl-2-oxa-5α-androstan-3-one (C-2 replaced by O in the androstane nucleus); an androgenic anabolic steroid.

oxaphenamide
oxaphenamide (ok-sa-fen′a-mid)

A choleretic.

oxazepam
oxazepam (ok-sa′ze-pam)

A benzodiazepine chemically and pharmacologically related to chlordiazepoxide and diazepam; an antianxiety agent.

oxazin
oxazin (ok′sa-zin)

Parent substance of a series of biologic dyes, e.g., gallocyanin, brilliant cresyl blue, cresyl violet acetate.

oxazole
oxazole (ok′sa-zol)

The fundamental ring system of pyranoses.

oxazolidinediones
oxazolidinediones (ok-sa-zo-lid′in-de-onz)

An obsolescent chemical class of antiepileptic drugs useful in the treatment of absence (petit mal) seizures; examples include trimethadione and paramethadione.

oxazolidinones
oxazolidinones (oks′a-zo-lid′i-nonz)

A new class of antibacterial antibiotics.

oxeladin
oxeladin (ok-sel′a-din)

An antitussive agent.

oxiconazole
oxiconazole (ok′se-ko′na-zol)

Broad-spectrum antifungal agent resembling ketoconazole.

oxidant
oxidant (ok′si-dant)

The substance that is reduced and that, therefore, oxidizes the other component of an oxidation-reduction system.

oxidase
oxidase (ok′si-das)

Classically, one of a group of enzymes, now termed oxidoreductases (EC class 1), that bring about oxidation by the addition of oxygen to a metabolite or by the removal of hydrogen or of one or more electrons. O. is now used for those cases in which O₂ acts as an acceptor (of H or of electrons); those removing hydrogen are now termed dehydrogenases. For individual oxidases, see the specific names.
direct o. originally, an o. catalyzing the transfer of O₂ directly to other bodies; now termed oxygenase.
indirect o. originally, an o. that acts by reducing a peroxide; now termed peroxidase.
terminal o. the last protein in the electron transport, respiratory chain. In mammals this is cytochrome c o..

oxidasis
oxidasis (ok-si-da′sis)

Oxidation by an oxidase.

oxidation
oxidation (ok-si-da′shun)

1. Combination with oxygen. 2. Increasing the valence of an atom or ion by the loss from it of hydrogen or of one or more electrons thus rendering it more electropositive, as when iron is changed from the ferrous (2+) to the ferric (3+) state. 3. In bacteriology, the aerobic dissimilation of substrates with the production of energy and water; in contrast to fermentation, the transfer of electrons in the o. process is accomplished via the respiratory chain, which utilizes oxygen as the final electron acceptor.
alpha-o., α-o. a form of o. of fatty acids in which carbons are removed one at a time in the form of CO₂; the α-carbon is first hydroxylated and then converted into a carbonyl; a deficiency of this pathway is associated with Refsum disease.
beta-o., β-o. 1. o. of the β-carbon (carbon 3) of a fatty acid, forming the β-keto (β-oxo) acid analog; of importance in fatty acid catabolism; 2. the entire pathway for the catabolism of saturated fatty acids containing an even number of carbon atoms; beta-o. (1) is a part of this pathway; acetyl-CoA is a major product of this pathway.
end o. the last o. step in a catabolic pathway. SYN: terminal o..
omega-o., ω-o. o. at the carbon atom farthest removed (ω-carbon) from the carboxyl group (carbon 1); thus, in this pathway, a dicarboxylic acid is formed; an important pathway in the degradation of prostaglandins.
terminal o. SYN: end o..

oxidation-reduction
oxidation-reduction

Any chemical oxidation or reduction reaction, which must, in toto, comprise both oxidation and reduction; the basis for calling all oxidative enzymes (formerly oxidases) oxidoreductases. Often shortened to “redox.”

oxidative
oxidative (ok-si-da′tiv)

Having the power to oxidize; denoting a process involving oxidation.

oxide
oxide (ok′sid)

A compound of oxygen with another element or a radical; e.g., mercuric o., HgO.
acid o. an acid anhydride; an o. of an electronegative element or radical; it can combine with water to form an acid.
basic o. a base anhydride; an o. of an electropositive element or radical; it can combine with water to form a base.
indifferent o. SYN: neutral o..
neutral o. an o. that is neither an acid nor a base; e.g., water (hydrogen o., H₂O). SYN: indifferent o..

oxidize
oxidize (ok′si-diz)

To combine or cause an element or radical to combine with oxygen or to lose electrons.

oxidoreductase
oxidoreductase (ok′si-do-re-duk′tas)

An enzyme (EC class 1) catalyzing an oxidation-reduction reaction. Trivial names for oxidoreductases include dehydrogenase, reductase, oxidase (where O₂ is the H acceptor), oxygenase (where O₂ is incorporated into the substrate), peroxidase (H₂O₂ is the acceptor; catalase is an exception), and hydroxylase (coupled oxidation of two donors). SEE ALSO: oxidase.

oxime
oxime (ok′sem)

A compound resulting from the action of hydroxylamine, NH₂OH, on a ketone or an aldehyde to yield the group &dbond;N–OH attached to the former carbonyl carbon atom.
amide oximes SYN: amidoximes.

oximeter
oximeter (ok-sim′e-ter)

An instrument for determining photoelectrically the oxygen saturation of a sample of blood.
cuvette o. an o. that reads the percentage of oxygen saturation of the blood as it passes through a cuvette outside the body.

oximetry
oximetry (oks-im-a-tree)

Procedure using a device to measure oxygen saturation by fluctations of light absorption in well-vascularized tissue during systole and diastole. The underlying principle is Beer law, or the relationship between the amount of light absorbed by a solute in solution and the concentration of the unknown solute.
pulse o. o. performed noninvasively, usually on the finger or ear lobe, in which the small increase in absorption of light during the systolic pulse is used to calculate oxygen saturation.

oxirane
oxirane (oks′e-ran)

SYN: ethylene oxide.

oxo- oxo-

Prefix denoting addition of oxygen; used in place of keto- in systematic nomenclature. SEE ALSO: hydroxy-, oxa-, oxy-.

oxoacetic acid
oxoacetic acid (ok′so-a-se′tik)

SYN: glyoxylic acid.

oxo acid
oxo acid (ok′so)

SYN: keto acid.

3-oxoacid-CoA transferase
3-oxoacid-CoA transferase

An enzyme catalyzing the reversible conversion of acetoacetyl-CoA and succinate into succinyl-CoA and acetoacetate; malonyl-CoA can substitute for succinyl-CoA and a few other 3-oxo acids for the acetoacetate; an important step in order for the ketone bodies to serve as a fuel for extrahepatic tissues. SYN: 3-ketoacid-CoA transferase, acetoacetyl-succinic thiophorase.

3-oxoacyl-ACP reductase
3-oxoacyl-ACP reductase (ok′so-as′il)

A part of the fatty acid synthase complex; an enzyme reversibly reacting 3-oxoacyl-ACP (ACP = acyl carrier protein) with NADPH to form d-3-hydroxyacyl-ACP and NADP⁺. SYN: β-ketoacyl-ACP reductase.

3-oxoacyl-ACP synthase
3-oxoacyl-ACP synthase

An enzyme condensing malonyl-ACP (ACP = acyl carrier protein) and acyl-Cys-protein to 3-oxoacyl-ACP + Cys-protein + CO₂, and similar reactions, as steps in fatty acid synthesis; Cys-protein is also a part of the fatty acid synthase complex. SYN: acyl-malonyl-ACP synthase, β-ketoacyl-ACP synthase.

2-oxoglutarate dehydrogenase
2-oxoglutarate dehydrogenase (ok′so-gloo-tar′at)

SYN: α-ketoglutarate dehydrogenase.

2-oxoglutaric acid
2-oxoglutaric acid (oks′-o-gloo-tar-ik)

SYN: α-ketoglutaramic acid.

2-oxo-5-guanidovaleric acid
2-oxo-5-guanidovaleric acid (gwan-e′do-va-ler′ik)

The deaminated derivative of arginine.

oxolamine
oxolamine (ok-sol′a-men)

Used for treatment of bronchopulmonary infections.

oxolinic acid
oxolinic acid (ok-so-lin′ik)

A quinolone antibacterial agent used in the treatment of urinary tract infections.

oxophenarsine hydrochloride
oxophenarsine hydrochloride (ok′so-fen-ar′sen)

An antisyphilitic and antitrypanosomal agent.

5-oxoprolinase
5-oxoprolinase

An enzyme that catalyzes the ATP-dependent hydrolysis of l-5-oxoproline (ATP + l-5-oxoproline → ADP + orthophosphate + l-glutamate); a deficiency of this enzyme will result in 5-oxoprolinuria.

5-oxoproline
5-oxoproline (Glp) (oks′o-pro′len)

A keto derivative of proline that is formed nonenzymatically from glutamate, glutamine, and γ-glutamylated peptides; it is also produced by the action of γ-glutamylcyclotransferase; elevated levels of o. are often associated with problems of glutamine or glutathione metabolism. SYN: 5-pyrrolidone-2-carboxylic acid, pyroglutamic acid, pyrrolidone-5-carboxylate.

4-oxoproline reductase
4-oxoproline reductase

SYN: 4-hydroxyproline oxidase.

5-oxoprolinuria
5-oxoprolinuria (oks′o-pro′len-ur-e-a)

Elevated levels of 5-oxoproline in the urine.

17-oxosteroids
17-oxosteroids (ok-so-ster′oydz)

SYN: 17-ketosteroids.

oxosuccinic acid
oxosuccinic acid (ok′so-suk-sin′ik)

SYN: oxaloacetic acid.

oxotremorine
oxotremorine (ok′so-trem′er-en)

An active metabolite of tremorine. Used as a pharmacologic tool for producing a parkinsonian tremor.

oxprenolol hydrochloride
oxprenolol hydrochloride (oks-pren′o-lol)

A β-receptor blocking agent with coronary vasodilator activity.

OXT
OXT

Abbreviation for oxytocin.

oxtriphylline
oxtriphylline (oks-tri′fi-lin, oks′tri-fil′in)

A true salt of theophylline; it has mild diuretic, myocardial stimulating vasodilator, and bronchodilator actions, with the same uses as theophylline, but is better absorbed and less irritating. SYN: choline theophyllinate.

oxy- oxy-

1. Combining form denoting shrill; sharp, pointed; quick (incorrectly used for ocy-, from G. okys, swift). 2. In chemistry, combining form denoting the presence of oxygen, either added or substituted, in a substance. SEE ALSO: hydroxy-, oxa-, oxo-. [G. oxys, keen]

oxyacoia
oxyacoia, oxyakoia (ok′se-a-koy′a)

Increased sensitiveness to sounds, occurring in facial paralysis, especially when the stapedius muscle is paralyzed. [G. oxys, acute, + akoe, hearing]

oxyaphia
oxyaphia (ok-se-a′fe-a)

SYN: hyperaphia. [G. oxys, acute, + haphe, touch]

oxybarbiturates
oxybarbiturates (ok′se-bar-bit′ur-ats)

Hypnotics of the barbiturate group in which the atom attached at the carbon-2 position is oxygen; virtually all hypnotic barbituates are oxybarbituates.

oxybenzone
oxybenzone (ok-se-ben′zon)

An ultraviolet screen for use in skin ointments and lotions.

oxybiotin
oxybiotin (ok-se-bi′o-tin)

An analog and antimetabolite of biotin, in which the sulfur atom is replaced by oxygen.

oxybutynin chloride
oxybutynin chloride (ok-se-bu′ti-nin)

An intestinal antispasmodic.

oxycalorimeter
oxycalorimeter (ok′se-kal-o-rim′e-ter)

A calorimeter measuring energy content of substances in terms of oxygen consumed.

oxycellulose
oxycellulose (ok-se-sel′u-los)

Cellulose that has been oxidized by NO₂ or other oxidizing agents to the point at which all or most of the glucose residues have been converted to glucuronic acid residues; used as an adsorbent in chromatography or other adsorption processes. SEE ALSO: oxidized cellulose.

oxycephalia
oxycephalia (ok′se-se-fa′le-a)

SYN: oxycephaly.

oxycephalic
oxycephalic, oxycephalous (ok-se-se-fal′ik, -sef′a-lus)

Relating to or characterized by oxycephaly. SYN: acrocephalic, acrocephalous.

oxycephaly
oxycephaly (ok-se-sef′a-le)

A type of craniosynostosis in which there is premature closure of the lambdoid and coronal sutures, resulting in an abnormally high, peaked, or conical skull. SYN: acrocephalia, acrocephaly, hypsicephaly, hypsocephaly, oxycephalia, steeple skull, tower skull, turricephaly. [G. oxys, pointed, + kephale, head]

oxychloride
oxychloride (ok-se-klor′id)

A compound of oxygen with a metallic chloride; e.g., a chlorate or perchlorate.

oxychromatic
oxychromatic (ok′se-kro-mat′ik)

SYN: acidophilic. [G. oxys, sour, acid, + chroma, color]

oxychromatin
oxychromatin (ok-se-kro′ma-tin)

Chromatin that stains with acid dyes, as in interphase nuclei. SYN: oxyphil chromatin.

oxycodone
oxycodone (ok-se-ko′don)

A narcotic analgesic often combined with aspirin or acetaminophen.

11-oxycorticoids
11-oxycorticoids (ok-se-kor′ti-koydz)

Corticosteroids bearing an alcohol or ketonic group on carbon-11; e.g., cortisone, cortisol.

oxygen
oxygen (O) (ok′se-jen)

1. A gaseous element, atomic no. 8, atomic wt. 15.9994 on the basis of ¹²C = 12.0000; an abundant and widely distributed chemical element, which combines with most of the other elements to form oxides and is essential to animal and plant life. 2. The molecular form of o., O₂. 3. A medicinal gas that contains not less than 99.0%, by volume, of O₂. [G. oxys, sharp, acid and genes, forming]
heavy o. SYN: o.-18.
hyperbaric o., high pressure o. o. at a pressure greater than 1 atm. SEE ALSO: hyperbaric oxygenation.
singlet o. an excited or higher-energy form of o. characterized by the spin of a pair of electrons in opposite directions, whereas electron spin is unidirectional in normal molecular o. Because of its great reactivity, singlet o. is a probable intermediate in most photo-oxidation reactions. Although it exists for no more than 0.1 second, it may react with atmospheric pollutants to foster smog formation and may have harmful biologic effects.
triplet o. the normal unexcited state of O₂ in the atmosphere, in which the unpaired pair of electrons are so displaced that their magnetic fields are oriented in the same direction, resulting in paramagnetism; each of the heat-generated spectral lines of such o. can be split by a magnetic field into a triplet. Cf.:singlet o..

oxygen-15
oxygen-15 (¹⁵O)

A cyclotron-produced, positron-emitting radioisotope of oxygen with a half-life of 122.2 seconds; used in studies of respiratory function and in positron emission tomography.

oxygen-16
oxygen-16 (¹⁶O)

The common oxygen isotope, making up 99.76% of natural oxygen.

oxygen-17
oxygen-17 (¹⁷O)

The rarest of the stable oxygen isotopes, making up 0.04% of natural oxygen.

oxygen-18
oxygen-18 (¹⁸O)

A stable oxygen isotope making up 0.20% of natural oxygen; used in mass spectrometry and in NMR studies of tissue. SYN: heavy oxygen.

oxygenase
oxygenase (ok′se-je-nas)

One of a group of enzymes (EC subclass 1.13) catalyzing direct incorporation of O₂ into substrates; e.g., tryptophan 2,3-dioxygenase (tryptophan pyrrolase) catalyzing reaction between O₂ and l-tryptophan to form N-l-formylkynurenine. Cf.:dioxygenase, monooxygenases.
mixed function o. any monooxygenase that catalyzes AH + O₂ + DH₂ → AOH + H₂O + D.

oxygenate
oxygenate (ok′se-je-nat)

To accomplish oxygenation.

oxygenation
oxygenation (ok′se-je-na′shun)

Addition of oxygen to any chemical or physical system.
apneic o. SYN: diffusion respiration.
hyperbaric o. an increased amount of oxygen in organs and tissues resulting from the administration of oxygen in a compression chamber at an ambient pressure greater than 1 atm.

oxygenic
oxygenic (ok-se-jen′ik)

Pertaining to or containing oxygen.

oxygenize
oxygenize (ok′se-jen-iz)

To oxidize with oxygen.

oxyheme
oxyheme (ok′se-hem)

SYN: hematin.

oxyhemochromogen
oxyhemochromogen (ok′se-hem′o-kro′mo-jen)

SYN: hematin.

oxyhemoglobin
oxyhemoglobin (HbO₂) (ok′se-he-mo-glo′bin)

Hemoglobin in combination with oxygen, the form of hemoglobin present in arterial blood, scarlet or bright red when dissolved in water. SYN: oxygenated hemoglobin.

oxyiodide
oxyiodide (ok-se-i′o-did)

A compound of oxygen with a metallic iodide, e.g., an iodate or periodate.

oxykrinin
oxykrinin (ok-se-krin′in)

SYN: secretin.

oxyluciferin
oxyluciferin (oks′e-loo-si′fer-in)

The activated derivative of luciferin formed in bioluminescence.

oxymesterone
oxymesterone (ok-se-mes′te-ron)

An anabolic steroid.

oxymetazoline hydrochloride
oxymetazoline hydrochloride (ok′se-me-taz′o-len)

A vasoconstrictor used topically to reduce swelling and congestion of the nasal mucosa.

oxymetholone
oxymetholone (ok-se-meth′o-lon)

An androgenic anabolic steroid.

oxymorphone hydrochloride
oxymorphone hydrochloride (ok-se-mor′fon)

A semisynthetic narcotic analgesic closely related chemically to hydromorphone hydrochloride; its actions are similar to those of morphine, but more potent.

oxymyoglobin
oxymyoglobin (MbO₂) (ok′se-mi-o-glo′bin)

Myoglobin in its oxygenated form, analogous in structure to oxyhemoglobin.

oxynervone
oxynervone (ok′se-ner′von)

SYN: hydroxynervone.

oxyntic
oxyntic (ok-sin′tik)

Acid forming, e.g., the parietal cells of the gastric glands. [G. oxyno, to sharpen, make sour, acid]

oxypertine
oxypertine (ok-se-per′ten)

An antianxiety agent; also available as the hydrochloride.

oxyphenbutazone
oxyphenbutazone (ok′se-fen-boo′ta-zon)

An orally effective analgesic and anti-inflammatory agent used (usually in short courses) for rheumatoid arthritis and gout.

oxyphencyclimine hydrochloride
oxyphencyclimine hydrochloride (ok′se-fen-si′kli-men)

The hydrochloride of 1,4,5,6-tetrahydro-1-methylpyrimidin-2-ylmethyl-α-cyclohexyl-α-hydroxy-α-phenylacetate; an anticholinergic agent.

oxyphenisatin acetate
oxyphenisatin acetate (ok′se-fe-ni′sa-tin)

A cathartic with pharmacologic properties resembling those of phenolphthalein, except that it is not absorbed from the gastrointestinal tract.

oxyphenonium bromide
oxyphenonium bromide (ok′se-fe-no′ne-um)

A quaternary ammonium compound with anticholinergic action.

oxyphil
oxyphil, oxyphile (ok′se-fil, -fil)

1. O. cell. 2. SYN: eosinophilic leukocyte. 3. SYN: oxyphilic. [G. oxys, sour, acid, + philos, fond]

oxyphilic
oxyphilic (ok-se-fil′ik)

Having an affinity for acid dyes; denoting certain cell or tissue elements. SYN: oxyphil (3) , oxyphile.

oxyphonia
oxyphonia (ok-se-fo′ne-a)

Shrillness or high pitch of the voice. [G. oxys, sharp, + phone, voice]

oxypolygelatin
oxypolygelatin (ok′se-pol-e-jel′a-tin)

A modified gelatin used as a plasma extender in transfusions.

oxypurine
oxypurine (ok-se-pur′en)

A purine containing oxygen; e.g., hypoxanthine, xanthine, uric acid.

oxypurinol
oxypurinol (ok′se-poor′i-nol)

Alloxanthine and inhibitor of xanthine oxidase; an active metabolite of allopurinol. The drug inhibits the formation of uric acid and is used in the treatment of gout.

oxyrhine
oxyrhine (ok′se-rin)

Having a sharp-pointed nose. [G. oxys, sharp, + rhis (rhin-), nose]

oxyrygmia
oxyrygmia (ok-se-rig′me-a)

Obsolete term for eructation of acid fluid. [G. oxys, acid, + erygmos, eructation]

Oxyspirura mansoni
Oxyspirura mansoni (ok′-se-spi-roo′ra man-so′ni)

A widely distributed spiruroid nematode parasite found under the nictitating membrane in the eye of turkeys, chickens, peafowl, quail, and grouse; larvae develop to the infective stage in cockroaches. SYN: Manson eye worm.

oxytalan
oxytalan (ok-sit′a-lan)

A type of connective tissue fiber histochemically distinct from collagen or elastic fibers described in the periodontal ligament and gingivae. [G. oxys, acid, + talas, suffering, resisting; coined term probably intended to mean “resistant to acid hydrolysis”]

oxytetracycline
oxytetracycline (ok′se-tet-ra-si′klen)

An antibiotic produced by the actinomycete, Streptomyces rimosus, present in the soil; its actions and uses are similar to those of tetracycline; available as the dihydrate, hydrochloride, and calcium.

oxythiamin
oxythiamin (ok-se-thi′a-min)

A molecule similar to that of thiamin but with a hydroxyl group replacing the amino group on the pyrimidine ring; a thiamin antagonist capable of inducing symptoms of thiamin deficiency on administration; increases thiamin excretion.

oxytocia
oxytocia (ok-se-to′se-a)

Rapid parturition. [G. okytokos, swift birth]

oxytocic
oxytocic (ok-se-to′sik)

1. Hastening childbirth. 2. SYN: parturifacient (2) .

oxytocin
oxytocin (OXT) (ok-se-to′sin)

A nonapeptide neurohypophysial hormone, differing from human vasopressin in having leucine at position 8 and isoleucine at position 3, that causes myometrial contractions at term and promotes milk release during lactation; used for the induction or stimulation of labor, in the management of postpartum hemorrhage and atony, and to relieve painful breast engorgement. SYN: ocytocin. [G. okytokos, swift birth]
arginine o. o. with arginine at position 8 (identical to arginine vasotocin). SEE ALSO: arginine vasopressin.

oxyuricide
oxyuricide (ok′se-u′ri-sid)

An agent that destroys pinworms. [oxyurid + L. caedo, to kill]

oxyurid
oxyurid (ok-se-u′rid)

Common name for members of the family Oxyuridae. [see Oxyuris]

Oxyuridae
Oxyuridae (ok-se-u′ri-de)

A family of parasitic nematodes (superfamily Oxyuroidea) found in the large intestine or cecum of vertebrates and the intestine of invertebrates, especially insects and millipedes; it includes the genera Aspiculurus, Enterobius, Oxyuris, Passalurus, Syphacia, and Thelandros.

Oxyuris
Oxyuris (ok′se-u′ris)

A genus of nematodes commonly called seatworms or pinworms (although the pinworm of humans is the closely related form, Enterobius vermicularis). O. equi, the horse pinworm, is a common parasite of horses in all parts of the world, inhabiting the large intestine. [G. oxys, sharp, + oura, tail]

-oyl -oyl

Suffix denoting an acyl radical; -yl replaces -ic in acid names.

oz.
oz.

Abbreviation for ounce.

ozena
ozena (o-ze′na)

SYN: atrophic rhinitis. [G. ozaina, a fetid polypus, fr. ozo, to smell]

ozenous
ozenous (o′ze-nus)

Relating to ozena.

ozocerite
ozocerite (o-zo-se′rit)

SYN: ozokerite.

ozokerite
ozokerite (o-zo-ker′it)

A mixture of paraffinic and cycloparaffinic hydrocarbons occurring in nature; it has a higher melting point than synthetic paraffin, and is used as a substitute for beeswax. SYN: ozocerite.
purified o. SYN: ceresin.

ozonator
ozonator (o′zo-na-ter, -tor)

An apparatus for generating ozone and diffusing it in the atmosphere of a room.

ozone
ozone (o′zon)

O₃;a powerful oxidizing agent; air containing a perceptible amount of O₃ formed by an electric discharge or by the slow combustion of phosphorus, and has an odor suggestive of Cl₂ or SO₂; also formed by the action of solar UV radiation on atmospheric O₂. [G. ozo, to smell]

ozonide
ozonide (o′zo-nid)

The unstable intermediate formed by the reaction of ozone with an unsaturated organic compound, especially with unsaturated fatty acids.

ozonolysis
ozonolysis (o-zo-nol′i-sis)

The splitting of a double bond in a hydrocarbon chain upon treatment with ozone, with the formation of two aldehydes (an ozonide is the unstable intermediate); has been used to determine the structure of unsaturated fatty acids. [ozone + G. lysis, dissolution]

ozonometer
ozonometer (o-zo-nom′e-ter)

A modified form of ozonoscope, in which by a series of test papers the amount of ozone in the atmosphere may be estimated.

ozonoscope
ozonoscope (o-zo′no-skop)

Filter paper saturated with starch and potassium iodide or with litmus and potassium iodide; turns blue in the presence of ozone.

ozostomia
ozostomia (o-zo-sto′me-a)

SYN: halitosis. [G. ozo, to smell, + stoma, mouth]

O-phosphono- O-phosphono-

Prefix indicating a phosphonic acid radical (–PO₃H₂) attached through an oxygen atom, hence a phosphoric ester. SEE ALSO: phospho-.

O-phosphoserine
O-phosphoserine (fos-fo-ser′en)

The phosphoric ester of serine; found as a constituent in many proteins ( e.g., phosphorylase a and phosvitin).

o-phthalaldehyde
o-phthalaldehyde (thal-al′de-hid)

A reagent used in the identification and the detection of amino acid.

O-succinylhomoserine (thiol)-lyase
O-succinylhomoserine (thiol)-lyase (suk′si-nil-ho′mo-ser′en)

An enzyme catalyzing the reaction between cystathionine and succinate to form l-cysteine and O-succinyl-l-homoserine. SYN: cystathionine γ-synthase.

12-O-tetradecanoylphorbol 13-acetate
12-O-tetradecanoylphorbol 13-acetate (TPA, tPA) (tet′ra-dek′a-no-il-for′bol)

A double ester of phorbol found in croton oil; a cocarcinogen or tumor promoter.