Copy of `Dorland's Medical Dictionary`

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Dorland's Medical Dictionary Category: Health and Medicine > Medical Dictionary Date & country: 31/12/2010, USA Words: 39128

arachnitis
(ar″ak-ni´tis) arachnoiditis.

arachnodactyly
(ә-rak″no-dak´tә-le) extreme length and slenderness of the fingers or toes, as in Marfan syndrome.

arachnoid
(ә-rak´noid) resembling a spiderweb. the delicate membrane interposed between the dura mater and the pia mater, and with them constituting the meninges.

arachnoid cap cell
a type of epithelial cell in the arachnoid membrane; these are the cells of origin of some types of meningiomas.

arachnoid cyst
a fluid-filled cyst between the layers of the leptomeninges, lined with arachnoid membrane, usually in the sylvian fissure.

arachnoid membrane
arachnoid.

arachnoid sheath
the delicate membrane between the pial sheath and the dural sheath of the optic nerve.

arachnoiditis
(ә-rak″noid-i´tis) inflammation of the arachnoid.

arachnophobia
(ә-rak″no-fo´be-ә) irrational fear of spiders.

Aralen
(ār´ә-len) trademark for a preparation of chloroquine, an antimalarial agent also used as a suppressant of lupus erythematosus.

Aran-Duchenne disease
(ah-rahn´ du-shen´) spinal muscular atrophy.

Aran-Duchenne muscular atrophy
spinal muscular atrophy.

arbor
(ahr´bәr) pl. ar´bores Latin word meaning tree. arbor vitae (of cerebellum) treelike outlines seen in a median section of the cerebellum. (of uterus) palmate folds. the tree Thuja occidentalis; its leafy twigs contain the medicinal substance thuja bu...

arborescent
(ahr″bә-res´әnt) branching like a tree; called also dendriform.

arborization
(ahr″bә-rĭ-za´shәn) a collection of branches, as the branching terminus of a nerve-cell process.

arbovirus
(ahr´bo-vi″rәs) a term used by epidemiologists to refer to any of numerous viruses that replicate in blood-feeding arthropods such as mosquitoes and ticks and are transmitted to humans by biting. adj., arbovi´ral., adj.

arbutamine
(ahr-bu´tә-mēn″) a synthetic catecholamine used as a diagnostic aid in cardiac stress testing in patients unable to exercise sufficiently for the test; administered as the hydrochloride salt.

ARC
AIDS-related complex; American Red Cross.

arc
(ahrk) a part of the circumference of a circle, or a regularly curved line. binauricular arc the arc across the top of the head from one auricular point to the other. reflex arc the circuit traveled by impulses producing a reflex action: receptor organ, aff...

arc guidance system
an apparatus used in stereotactic surgery, consisting of a metal arc-shaped band or bar with degree markings and an attachment for an electrode that is positioned by moving through the arc to aim at a precise location in the brain.

arc welder's disease
arc welder's lung welder's lung.

arcate
(ahr´kāt) arcuate.

arch
(ahrch) a structure of bowlike or curved outline.

arch of aorta
aortic arch.

Archaea
(ahr-ke´ә) in the three-domain system of classification, one of the two large divisions into which prokaryotes are grouped. They are genetically distinct from bacteria and share some features with the eukaryotes. They have a variety of shapes and sizes, may or may not have a cell wall, and occur as single cells and as f...

archencephalon
(ahrk″әn-sef´ә-lon) the primordial brain from which the midbrain and forebrain develop.

archenteron
(ahrk-en´tәr-on) the central cavity that is the provisional gut in the gastrula; the primordial digestive cavity of the embryo.

archeocerebellum
(ahr″ke-o-ser″ә-bel´әm) the phylogenetically old part of the cerebellum.

archeocortex
(ahr″ke-o-kor´teks) archicortex.

arches of foot
the longitudinal and transverse arches of the foot. The longitudinal arch comprises the medial arch or pars medialis, formed by the calcaneus, talus, and the navicular, cuneiform, and the first three tarsal bones; and the lateral arch or pars lateralis, formed by the calcaneus, the cuboid bone, and the lateral two metatarsal bones. T...

archetype
(ahr´kә-tīp) in Jung's analytic psychology, a structural component of the collective unconcious, which is an inherited idea derived from the life experience of all of the members of the race and contained in the individual unconscious. The archetypes are the ideas, modes of thought, and patterns of reac...

archicortex
(ahr″kĭ-kor´teks) that portion of the cerebral cortex that, with the paleocortex, develops in association with the olfactory system, and which is phylogenetically older than the neocortex and lacks its layered structure. Called also archeocortex and archipallium.

archinephron
(ahr″kĭ-nef´ron) a unit of the pronephros.

archipallium
(ahr″kĭ-pal´e-әm) archicortex.

arciform
(ahr´sĭ-form) arcuate.

arctation
(ahrk-ta´shәn) stenosis.

Arctic anemia
polar anemia.

arcuate
(ahr´ku-āt) bent like a bow.

arcuate arteries of kidney
origin, interlobar artery; branches, interlobular artery and straight arterioles; distribution, parenchyma of kidney.

arcuate arteries of uterus
branches of the uterine artery that run circumferentially in the uterine wall as anterior and posterior groups, anastomosing across the midline both anteriorly and posteriorly, and giving rise to radial arteries that supply deeper layers.

arcuate artery of foot
origin, dorsalis pedis artery; branches, deep plantar branch and dorsal metatarsal arteries; distribution, foot, toes.

arcuate fibers
any of the bow-shaped fibers in the brain, such as those connecting adjacent gyri in the cerebral cortex, or the external or internal arcuate fibers of the medulla oblongata.

arcuate ligaments
the arched ligaments that connect the diaphragm with the lowest ribs and the first lumbar vertebra.

arcuate nuclei of medulla oblongata
small irregular areas of gray matter on the ventromedial aspect of the pyramids of the medulla oblongata.

arcuate scotoma
an arc-shaped defect of vision arising in an area near the blind spot and extending toward it.

arcuate veins of kidney
a series of complete arches across the bases of the renal pyramids; they are formed by union of the interlobular veins and the straight venules and drain into the interlobar veins.

arcuation
(ahr-ku-a´shәn) a bending or curvature.

arcus
(ahr´kәs) Latin word meaning arch, or bow.

arcus adiposus
(ahr´kәs ad-ĭ-po´sәs) arcus corneae.

arcus corneae
(ahr´kәs kor´ne-e) an abnormal white or gray opaque ring at the outer edge of the cornea. Sometimes it is present at birth or appears in childhood and is called arcus juvenilis). It is particularly common in people over 50 years old and is then given the name arcus senilis. It results from deposits of cholesterol in the...

arcus juvenilis
(ahr´kәs joo-vә-ni´lis) arcus corneae in young persons.

arcus senilis
(ahr´kәs se-ni´lis) arcus corneae in the elderly.

ardeparin
(ahr-de-par´in) a low molecular weight heparin administered subcutaneously as the sodium salt as an anticoagulant and antithrombotic for prevention of deep vein thrombosis and pulmonary thromboembolism after knee replacement surgery.

ARDS
adult respiratory distress syndrome.

area
(ār´e-ә) pl. a´reae, areas a limited space or plane surface.

area subcallosa
(ār´e-ә sәb-kә-lo´sә) Broca parolfactory area.

areflexia
(a″re-flek´se-ә) absence of the reflexes. detrusor areflexia absence of contractions of the detrusor muscles of the urinary bladder.

aregenerative anemia
an anemia characterized by bone marrow failure, so that functional marrow cells are regenerated slowly or not at all; the term has been used to denote specific disorders with this characteristic, including aplastic anemia and pure red cell anemia.

Arenaviridae
the arenaviruses, a family of RNA viruses containing just one genus, Arenavirus.

arenavirus
(ә-re´nә-vi″rәs) any virus of the family Arenaviridae.

Arenavirus
(ә-re´nә-vi″rәs) the single genus of the family Arenaviridae, including several that cause hemorrhagic fevers and the viruses of the Tacaribe complex. The natural hosts are rodents.

areola
(ә-re´o-lә) pl. are´olae a narrow zone surrounding a central area, such as the darkened area surrounding the nipple of the mammary gland. any minute space or interstice in a tissue.

areolar
(ә-re´o-lәr) containing minute spaces. pertaining to an areola.

areolar central choroiditis
areolar choroiditis a type that starts around or near the macula lutea and progresses toward the periphery. Unlike in other types, lesions in this type first are pigmented but then lose their pigmentation. Called also Förster choroiditis or disease.

areolar glands
Montgomery glands.

areolar tissue
connective tissue made up largely of interlacing fibers.

Argas
(ahr´gәs) a genus of ticks parasitic in poultry, other birds, and sometimes humans.

Argasidae
(ahr-gas´ĭ-de) a family of arthropods, the soft ticks.

argatroban
(ahr-gat´ro-ban″) an anticoagulant that binds to the thrombin active site and inhibits various thrombin-catalyzed reactions; used in the prophylaxis and treatment of thrombocytopenia resulting from treatment with heparin, administered intravenously.

argemone oil
an oil, derived from the seeds of the prickly poppy (Argemone mexicana), that contains a toxin that causes epidemic dropsy. In some parts of the world, it sometimes occurs as a contaminant of cooking oil.

argentaffin
(ahr-jen´tә-fin) staining readily with silver salts; see also argentaffin cells.

argentaffinoma
(ahr″jәn-taf″ĭ-no´mә) a carcinoid tumor of the gastrointestinal tract formed from argentaffin cells, usually in the terminal ileum or appendix. Such tumors elaborate a variety of catecholamines that produce the symptom complex called carcinoid syndrome.

argentaffinoma syndrome
the most common type of carcinoid syndrome, in which the tumor arises from the argentaffin cells of the gastrointestinal tract.

Argentine hemorrhagic fever
Argentinian hemorrhagic fever a hemorrhagic fever primarily affecting agricultural workers in northern Argentina, caused by the Junin virus and transmitted by contact with the excreta of infected rodents, especially of the genus Calomys. Characteristics include high fever, leukopenia, thrombocytopenia, generalized myalgia, hemorrhagic...

Argentine hemorrhagic fever virus
Junin virus.

arginase
(ahr´jĭ-nās) an enzyme of the liver that splits arginine into urea and ornithine.

arginine
(Arg) (R) (ahr´jĭ-nēn) a nonessential amino acid that occurs in proteins and is involved in the urea cycle and in the synthesis of creatine. Preparations of the base or the glutamate or hydrochloride salt are used in the treatment of hyperammonemia and in the assessment of pituit...

argininosuccinic acid
(ahr″jĭ-ne″no-suk-sin´ik) a compound normally formed in urea formation in the liver, but not normally present in urine.

argininosuccinicaciduria
(ahr″jĭ-ne″no-suk-sin″ik-as″ĭ-du´re-ә) excretion in the urine of argininosuccinic acid, a feature of an inborn error of metabolism marked also by mental retardation.

argipressin
(ahr″jĭ-pres´in) arginine vasopressin.

argon
(Ar) (ahr´gon) a chemical element, atomic number 18, atomic weight 39.948.

argon laser
a laser with ionized argon as the active medium and with a beam in the blue and green visible light spectrum; used for photocoagulation.

Argyll Robertson pupil
one that is miotic and responds to accommodation effort, but not to light.

Argyll Robertson pupil sign
Argyll Robertson pupil.

argyria
(ahr-jir´e-ә) poisoning by silver or its salts, usually from either industrial or medicinal exposure. Chronic argyria is marked by a permanent ash gray discoloration of the skin, conjunctivae, and internal organs, and there is usually a slate blue “silver line” on the gingival margin.

argyric
(ahr-jir´ik) pertaining to silver.

argyrism
(ahr´jә-riz-әm) argyria.

argyrophil
(ahr´jә-ro-fil) (ahr-ji´ro-fil) easily impregnated with silver; said of cells or tissues that bind with silver salts, which can then be reduced to produce a brown or black stain.

argyrosis
(ahr″jә-ro´sis) argyria.

arhinia
(ә-rin´e-ә) congenital absence of the nose. Spelled also arrhinia.

Arias-Stella cells
(ahr´yahs-sta´yә) columnar cells in the endometrium of the uterus that have a hyperchromatic enlarged nucleus; they appear to be associated with chorionic tissue in an intrauterine or extrauterine site.

Arias-Stella reaction
(ahr´yahs-sta´yә) nuclear and cellular hypertrophy of the endometrial epithelium associated with ectopic pregnancy.

ariboflavinosis
(a-ri″bo-fla″vĭ-no´sis) deficiency of vitamin B2 (riboflavin) in the diet; symptoms include lesions around the mouth and elsewhere on the face, malaise, weakness, and weight loss; in severe cases, persons may suffer from anemia, corneal or other eye changes, and seborrheic dermatitis. It is most common ...

Aries-Pitanguy mammaplasty
Aries-Pitanguy operation a type of reduction mammaplasty to reduce mild to moderate largeness of the breasts.

Aristocort
(ә-ris´to-cort) trademark for preparations of triamcinolone, a prednisolone derivative that is a steroid antiinflammatory agent.

arm
(ahrm) the part of the upper limb from the shoulder to the elbow; called also brachium. in common usage, the entire upper limb. a slender part or extension that projects from a main structure. chromosome arm either of the two segments of the chromosome separate...

arm ergometry exercise test
a variant of the bicycle ergometer exercise test in which the patient uses the arms to pedal the bicycle.

arm phenomenon
Pool phenomenon (def. 2).

armamentarium
(ahr″mә-men-tar´e-әm) the entire equipment of a practitioner, such as medicines, instruments, and books.

Armanni-Ebstein cells
vacuolated epithelial cells in the proximal straight tubules of the kidney, containing deposits of glycogen. See also Armanni-Ebstein lesion.