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Medical Dictionary


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 (o-per′ku-lar)
Relating to an operculum.

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 (o-perk-u-li′tis)
Originating under an operculum. [operculum + G. -itis, inflammation]

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 (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 (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 (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 (o′fi-di′a-sis)
Poisoning by a snake. SYN: ophidism. [G. ophidion, dim. of ophis, a serpent]

ophidiophobia (o-fid′e-o-fo′be-a)
Morbid fear of snakes. [G. ophidion, a small snake, + phobos, fear]

ophidism (o′fid-izm)
SYN: ophidiasis.

ophritis (of-ri′tis)
Dermatitis in the region of the eyebrows. SYN: ophryitis. [G. ophrys, eyebrow, + -itis, inflammation]

ophryitis (of-re-i′tis)
SYN: ophritis.

ophryogenes (of′re-yo-jen-′enz)
Related to the eyebrows. [Mod. L., fr. G. ophrys, eyebrow, + suffix -genes, arising from]

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 (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 (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]

See ophthalmo-.

ophthalmalgia (of′thal-mal′je-a)
SYN: oculodynia. [ophthalmo- + G. algos, pain]

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 (of-thal′mik)
Relating to the eye. SYN: ocular (1) . [G. ophthalmikos]

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

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 (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 (of-thal′mo-lith)
SYN: dacryolith. [ophthalmo- + G. lithos, stone]

ophthalmologist (of-thal-mol′o-jist)
A specialist in ophthalmology. SYN: oculist.

ophthalmology (of-thal-mol′o-je)
The medical specialty concerned with the eye, its diseases, and refractive errors. [ophthalmo- + G. logos, study]

ophthalmomalacia (of-thal′mo-ma-la′she-a)
Abnormal softening of the eyeball. [ophthalmo- + G. malakia, softness]

ophthalmomelanosis (of-thal′mo-mel-a-no′sis)
Melanotic discoloration of the conjunctiva and adjoining tissues.

ophthalmometer (of-thal-mom′e-ter)
SYN: keratometer. [ophthalmo- + G. metron, measure]

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 (of-thal′mo-mi-i′a-sis)
SYN: ocular myiasis.

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 (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 (of-thal-mo-ple′jik)
Relating to or marked by ophthalmoplegia.

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 (of′thal-mo-skop′ik)
Relating to examination of the interior of the eye.

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 (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 (of-thal′mo-vas′ku-lar)
Relating to the blood vessels of the eye.

Vision. [G. ops, eye]

opianine (o-pi′a-nen)
SYN: noscapine.

opianyl (o′pi-a-nil)
SYN: meconin.

opiate (o′pe-at)
Any preparation or derivative of opium.

opine (o′pen)
A derivative of basic amino acids, produced by crown-gall tumors in plants.

opiocortin (o′pe-o-kor′tin)
SYN: opiomelanocortin.

opioid (o′pe-oyd)
Originally, a term denoting synthetic narcotics resembling opiates but increasingly used to refer to both opiates and synthetic narcotics.

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

opisthenar (o-pis′the-nar)
Dorsum of the hand. [G. back of the hand, from opisthen, behind, + thenar, palm of the hand]

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 (o-pis′the-on)
The middle point on the posterior margin of the foramen magnum, opposite the basion. [G. opisthios, posterior]

opisthionasial (o-pis′the-o-na′ze-al)
Relating to the opisthion and the nasion; denoting the distance between the two points.

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

opisthocheilia, opisthochilia (op′is-tho-ki′le-a)
Recession of the lips. [opistho- + G. cheilos, lip]

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 (op′is-thor-ki′a-sis)
Infection with the Asiatic liver fluke, Opisthorchis viverrini, or other opisthorchids.

opisthorchid (op-is-thor′kid)
Common name for members of the family Opisthorchiidae.

Opisthorchiidae (op′is-thor-ke′i-de)
A family of trematodes that includes the genera Opisthorchis and Clonorchis.

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 (op-is-tho′tik)
Behind the ear. [opistho- + G. ous (ot-), ear]

opisthotonic (op-is-thot′o-nik, o-pis′tho-ton′ik)
Relating to or characterized by opisthotonos.

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

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

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..

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

opobalsamum (op-o-bal′sa-mum)
SYN: balm of Gilead. [G. opobalsamon, the juice of the balsam tree, fr. opos, juice, + balsamon]


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