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Medical Dictionary


orthetics (or-thet′iks)
SYN: orthotics.

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 (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 (or′tho-kan)
The methyl ester of 3-amino-4-hydroxybenzoic acid; a surface anesthetic agent usually used in dusting powder form.

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 (or-tho-sef′a-lus)
SYN: orthocephalic.

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, orthochromophile (or-tho-kro′mo-fil, -fil)
SYN: orthochromatic. [ortho- + G. chroma, color, + philos, fond]

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 (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 (or-tho-den′tin)
Straight tubed dentin as seen in the teeth of mammals.

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 (or-tho-dij′i-tah)
Correction of malformations of fingers or toes. [ortho- + L. digitus, finger or toe]

orthodontia (or-tho-don′she-a)
SYN: 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.

A dental specialist who practices orthodontics.

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 (or-tho-jen′e-sis)
The doctrine that evolution is governed by intrinsic factors and occurs in predictable directions. [ortho- + G. genesis, origin]

orthogenic (or-tho-jen′ik)
Relating to orthogenesis.

orthogenics (or-tho-jen′iks)
SYN: eugenics.

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, 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 (or′tho-grad)
Walking or standing erect; denoting the posture of humans; opposed to pronograde. [ortho- + L. gradior, pp. gressus, to walk]

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 (or′tho-ker-a-to′sis)
Formation of an anuclear keratin layer, as in the normal epidermis. [ortho- + G. keras, horn, + -osis, condition]

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 (or-tho-me-kan′i-kal)
Pertaining to braces, prostheses, orthotic devices, and appliances. [ortho- + mechanical]

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 (or-tho-me′lik)
Correcting malformations of arms or legs. [ortho- + G. melos, limb]

orthometer (or-thom′e-ter)
SYN: exophthalmometer. [ortho- + G. metron, measure]

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 (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, orthopedic (or-tho-pe′dik)
Relating to orthopedics.

orthopaedics (or-tho-pe′diks)
SYN: orthopedics. [ortho- + G. pais (paid-), child]

orthopaedist, orthopedist (or-tho-pe′dist)
One who practices orthopaedics.

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 (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 (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 (or-tho-for′ik)
Pertaining to orthophoria.

orthophosphate (or-tho-fos′fat)
A salt or ester of orthophosphoric acid. inorganic o. (Pi) any ion or salt form of phosphoric acid. SYN: inorganic phosphate.

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 (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 (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 (or′thop-ne′ik)
Relating to or characterized by orthopnea.

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 (or′tho-pros′the-sis, -pros-the′sis)
An appliance used in the management of prosthetic problems related to alignment of teeth.

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 (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 (or-thop′tik)
Relating to 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 (or-thop′tist)
One skilled in orthoptics.

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 (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, 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 (or-tho-stat′ik)
Relating to an erect posture or position.

orthostereoscope (or′tho-ster′e-o-skop)
A rarely used instrument for viewing stereoscopic radiographs.

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 (or-thot′iks)
The science concerned with the making and fitting of orthopaedic appliances. SYN: orthetics.

orthotist (or′tho′tist)
A maker and fitter of orthopaedic appliances.

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, 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 (or-tho-top′ik)
In the normal or usual position. [ortho- + G. topos, place]

orthotropic (or-tho-trop′ik)
Extending or growing in a straight, especially a vertical, direction. [ortho- + G. trope, a turn]

orthovoltage (or-tho-vol′tij)
In radiation therapy, a term for voltage between 400 and 600 kV.

Marius, 20th century Italian orthopaedic surgeon. See O. maneuver, O. test.

Samuel T., U.S. neurologist, 1879–1975. See Wolf-O. bodies, under body.

orycenin (or-e-sen′in)
A glutelin in rice. [G. oryza, rice, + -in]

Abbreviation for L. oculus sinister, left eye.

Symbol for osmium.

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, 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 (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-, oscheo-
The scrotum. [G. osche]

oscheal (os′ke-al)
SYN: scrotal.


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