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Medical Dictionary


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]

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

oppilative (op-i-la′tiv)
Obstructive to any secretion.

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 (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 (op′po-shur)
Bringing together of tissue during suturing.

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

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 (op-se-oo′re-a)
A more rapid excretion of urine during fasting than after a full meal. [G. opsi, late, + ouron, urine]

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 (op′so-jen)
SYN: opsinogen.

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 (op-son′ik)
Relating to opsonins or to their utilization.

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 (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 (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 (op-so-nom′e-tre)
Determination of the opsonic index or the opsonocytophagic activity.

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 (op-so-no-fil′ik)
Pertaining to, characterized by, or resulting in opsonophilia.

optic, optical (op′tik, op′ti-kal)
Relating to the eye, vision, or optics. [G. optikos]

optician (op-tish′an)
One who practices opticianry.

opticianry (op-tish′an-re)
The professional practice of filling prescriptions for ophthalmic lenses, dispensing spectacles, and making and fitting contact lenses.

See opto-.

opticociliary (op′ti-ko-sil′e-ar-e)
Relating to the optic and ciliary nerves.

opticopupillary (op′ti-ko-pu′pi-lar-e)
Relating to the optic nerve and the pupil.

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

optokinetic (op′to-ki-net′ik)
See o. nystagmus. [opto- + G. kinesis, movement]

optomeninx (op′to-me′ninks)
SYN: retina. [opto- + G. meninx, membrane]

optometer (op-tom′e-ter)
An instrument for determining the refraction of the eye. [opto- + G. metron, measure] objective o. SYN: refractometer.

optometrist (op-tom′e-trist)
One who practices 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 (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 (op′to-tips)
Test letters. See test types. [opto- + G. typos, type]

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

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.

ora1 (o′ra)
Plural of L. os, the mouth. [L.]

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

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

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.

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

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 [C.I. 16230]
An azo dye, used as a cytoplasmic stain in histologic techniques.

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.

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

orbicular (or-bik′u-lar)
Similar in form to an orb; circular in form. [L. orbiculus, a small disk, dim. of orbis, circle]

orbiculare (or-bik-u-la′re)
SYN: lenticular process of incus. [L., fr. orbiculus, a small disk]

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 (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 (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, gen. orbitae (or′bi-ta, -te) [TA]
SYN: orbit. [L. a wheel-track, fr. orbis, circle]

orbital (or′bi-tal)
Relating to the orbits.

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 (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 (or′bi-to-na′sal)
Relating to the orbit and the nose or nasal cavity.

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 (or′bi-to-nom′e-tre)
Measurement by means of the orbitonometer.

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]

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

orbitosphenoid (or′bi-to-sfe′noyd)
Relating to the orbit and the sphenoid bone.

orbitotomy (or-bi-tot′o-me)
Surgical incision into the orbit. [L. orbita, orbit, + tome, a cutting]

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 (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 (ork-al′-je-a)
SYN: orchialgia.

orchectomy (or-kek′to-me)
SYN: orchiectomy.

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

See orchio-.

orchi-, orchido-, orchio-
The testes. [G. orchis, testis]

orchialgia (or-ke-al′je-a)
Pain in the testis. SYN: orchalgia, orchiodynia, orchioneuralgia, testalgia. [orchi- + G. algos, pain]


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