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Medical Dictionary - Dictionary of Medicine and Human Biology


Medical Dictionary


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valve (valv) [TA]
1. A fold of the lining membrane of a canal or other hollow organ serving to retard or prevent a reflux of fluid. 2. Any formation or reduplication of tissue, or flaplike structure, resembling or functioning as a v.. SEE ALSO: valvule, plica. SYN: valva [TA] . [L. valva] Amussat v. SYN: spiral fold of cystic duct. anal valves [TA] delicate crescent-shaped mucosal folds that pass between the lower ends of neighboring anal columns; the small pocket thus formed is an anal sinus. SYN: valvulae anales [TA] , Morgagni valves. anterior urethral v. a crescentic horizontal fold in the proximal spongy urethra. aortic v. [TA] the v. between the left ventricle and the ascending aorta, consisting of three fibrous semilunar cusps (valvules), located in the adult in anterior, right posterior, and left posterior positions; they are named, however, in accordance with their embryonic derivation in which the anteriorly located cusp is the right cusp (above which the right coronary artery arises), the left posteriorly positioned cusp is designated as the left cusp (above which the left coronary artery arises), and the right posteriorly positioned cusp is designated as the posterior or noncoronary cusp. SYN: valva aortae [TA] . atrioventricular valves tricuspid v., mitral v.. A-V valves abbreviation for the cardiac atrioventricular valves; the mitral and tricuspid valves. ball v. any of a variety of prosthetic cardiac valves comprising a ball within a retaining cage affixed to the orifice; when appropriately sized, used in aortic, mitral, or tricuspid position. Bauhin v. SYN: ileal papilla. Béraud v. a small fold in the interior of the lacrimal sac at its junction with the lacrimal duct. SYN: Krause v.. bicuspid v. SYN: mitral v.. bi-leaflet v. a low profile mechanical heart v. that is less obstructive to outflow, especially in small size. biologic v. SYN: tissue v.. Björk-Shiley v. a low profile tilting disc mechanical heart v.. Blom-Singer v. a prosthesis for maintaining the patency of a tracheoesophageal puncture for vocal rehabilitation after laryngectomy. Bochdalek v. a fold of mucous membrane in the lacrimal canaliculus at the lacrimal punctum. SYN: Foltz valvule. Braune v. a fold of mucous membrane at the junction of the esophagus with the stomach. Carpentier-Edwards v. a bioprosthetic v. made from preserved porcine aortic valves. caval v. SYN: v. of inferior vena cava. congenital v. an abnormal lining fold obstructing a passage; e.g., of a mucous membrane in the urethra. coronary v. SYN: v. of coronary sinus. v. of coronary sinus [TA] a delicate fold of endocardium at the opening of the coronary sinus into the right atrium. SYN: valvula sinus coronarii [TA] , coronary v., thebesian v.. eustachian v. SYN: v. of inferior vena cava. v. of foramen ovale [TA] a fold projecting into the left atrium from the margin of the foramen ovale in the fetus; when, with beginning inspiration, the blood pressure within the left atrium increases, the v. closes and its edges become adherent to the margin of the foramen ovale, occluding it. SYN: valvula foraminis ovalis [TA] , falx septi, v. of oval foramen. Gerlach v. SYN: v. of vermiform appendix. Guérin v. SYN: v. of navicular fossa. Heister v. SYN: spiral fold of cystic duct. Heyer-Pudenz v. a v. used in the shunting procedure for hydrocephaly; consisting of a catheter-v. system in which the ventricular catheter leads the cerebrospinal fluid into a one-way pump through which the cerebrospinal fluid passes down the distal catheter into the right atrium of the heart. Hoboken valves the flangelike protrusions into the lumen of the umbilical arteries where they are twisted or kinked in their course through the umbilical cord. Huschke v. SYN: lacrimal fold. ileocecal v. SYN: ileal papilla. ileocolic v. SYN: ileal papilla. v. of inferior vena cava [TA] an endocardial fold extending from the anterior inferior margin of the inferior vena cava to the anterior part of the limbus fossa ovalis. SYN: valvula venae cavae inferioris [TA] , caval v., eustachian v., sylvian v.. Kerckring valves SYN: circular folds of small intestine, under fold. Krause v. SYN: Béraud v.. left atrioventricular v. mitral v.. Mercier v. an occasional fold of mucosa of the bladder partially occluding the ureteral orifice. mitral v. [TA] the v. closing the orifice between the left atrium and left ventricle of the heart; its two cusps are called anterior and posterior. SYN: valva atrioventricularis sinistra [TA] , left atrioventricular v.&star, valva mitralis&star, bicuspid v., valvula bicuspidalis. Morgagni valves SYN: anal valves. nasal v. the variable aperture between the nasal septum and the caudal margin of the upper lateral nasal cartilage. v. of navicular fossa [TA] an inconstant fold of mucous membrane sometimes found in the root of the navicular fossa of the urethra. SYN: valvula fossae navicularis [TA] , Guérin fold, Guérin v.. nonrebreathing v. a type of v. that prevents mixture of inhaled and exhaled gases. O'Beirne v. SYN: rectosigmoid sphincter. v. of oval foramen SYN: v. of foramen ovale. parachute mitral v. congenital abnormality of the mitral v. characterized by the presence of a single papillary muscle from which the chordae of both v. leaflets divide; thus the resemblance to a parachute; the condition often produces a stenosis as the combined result of the tugging action of the chordae on, and the subsequent narrowing between, the leaflets. SYN: parachute deformity. porcine v. stented heterograft v. from pigs. posterior urethral valves anomalous folds occurring at the level of the seminal colliculus. SYN: Amussat valvula. prosthetic valves valves used to replace human valves. They are divided into mechanical and tissue valves. The tissue is divided into homografts and heterografts. pulmonary v. [TA] the v. at the entrance to the pulmonary trunk from the right ventricle; it consists of semilunar cusps (valvules), which are usually arranged in the adult in right anterior, left anterior, and posterior positions; however, they are named in accordance with their embryonic derivation; thus the posteriorly located cusp is designated as the left cusp, the right anteriorly located cusp is designated the right cusp, and the left anteriorly positioned cusp is called the anterior cusp. SYN: valva trunci pulmonalis [TA] , pulmonic v., v. of pulmonary trunk. v. of pulmonary trunk SYN: pulmonary v.. pulmonic v. SYN: pulmonary v.. rectal valves SYN: transverse folds of rectum, under fold. reducing v. a v. designed to lower the pressure of a gas coming from a cylinder containing compressed gas under high pressure. right atrioventricular v. tricuspid v.. Rosenmüller v. SYN: lacrimal fold. semilunar v. [TA] a heart v. comprised of a set of three semilunar cusps (valvules); hence both the aortic and pulmonary valves are semilunar valves. SYN: valvula semilunaris [TA] . spiral v. of cystic duct SYN: spiral fold of cystic duct. Starr-Edwards v. a cage and ball artificial cardiac v. with high reliability and durability. sylvian v. SYN: v. of inferior vena cava. Tarin v. SYN: inferior medullary velum. Terrien v. a valvelike fold between the gallbladder and the cystic duct; the first ridge of the spiral fold of the cystic duct. thebesian v. SYN: v. of coronary sinus. tilting disk v. a variety of prosthetic cardiac v. composed of a caged disc. tissue v. a prosthetic cardiac v. derived from the pig heart, bovine pericardium, or other biologic source. SEE ALSO: prosthesis. SYN: biologic v.. tricuspid v. [TA] the v. closing the orifice between the right atrium and right ventricle of the heart; its three cusps are called anterior, posterior, and septal. SYN: valva atrioventricularis dextra [TA] , right atrioventricular v.&star, valva tricuspidalis&star, valvula tricuspidalis. Tulp v., Tulpius v. SYN: ileal papilla. urethral valves folds in the urethral mucous membrane. SEE ALSO: anterior urethral v., posterior urethral valves. v. of Varolius SYN: ileal papilla. venous v. [TA] a fold of the lining layer of a vein to prevent a reflux of blood. SYN: valvula venosa (2) [TA] . v. of vermiform appendix a fold of mucous membrane, simulating a v., sometimes found at the origin of the vermiform appendix. SYN: Gerlach v., valvula processus vermiformis. vesicoureteral v. a lock mechanism in the wall of the intravesical portion of the ureter that normally prevents urinary reflux. v. of Vieussens a prominent v. in the great cardiac vein where it turns around the obtuse margin to become the coronary sinus. Vieussens v. SYN: superior medullary velum.

valveless (valv′les)
Without valves; denoting certain veins, such as the portal, that are not provided with valves as are most of the veins.

valviform (val′vi-form)
Valve-shaped.

valvoplasty (val′vo-plas-te)
Surgical reconstruction of a deformed cardiac valve, for the relief of stenosis or incompetence. SYN: valvuloplasty. [valve + G. plastos, formed]

valvotomy (val-vot′o-me)
1. Cutting through a stenosed cardiac valve to relieve the obstruction. SYN: valvulotomy. 2. Incision of a valvular structure. [valve + G. tome, incision] mitral v. deliberate incision or enlargement by inserting a finger in the stenotic mitral valve. rectal v. cutting through rectal folds that are too rigid or large.

valvula, pl .valvulae (val′vu-la, -le) [TA]
SYN: valvule. [Mod. L. dim. of valva] Amussat v. SYN: posterior urethral valves, under valve. valvulae anales [TA] SYN: anal valves, under valve. v. bicuspidalis SYN: mitral valve. valvulae conniventes SYN: circular folds of small intestine, under fold. v. foraminis ovalis [TA] SYN: valve of foramen ovale. v. fossae navicularis [TA] SYN: valve of navicular fossa. Gerlach v. SYN: trabecular tissue of sclera. v. lymphatica [TA] SYN: lymphatic valvule. v. processus vermiformis SYN: valve of vermiform appendix. v. semilunaris [TA] SYN: semilunar valve. v. semilunaris anterior valvae trunci pulmonalis anterior semilunar cusp of the pulmonary valve. v. semilunaris dextra valvae aortae right semilunar cusp of the aortic valve. v. semilunaris dextra valvae trunci pulmonalis right semilunar cusp of the pulmonary valve. v. semilunaris posterior valvae aortae posterior semilunar cusp of the aortic valve. v. semilunaris sinistra valvae aortae left semilunar cusp of the aortic valve. v. semilunaris sinistra valvae trunci pulmonalis left semilunar cusp of the pulmonary valve. v. semilunaris tarini SYN: inferior medullary velum. v. sinus coronarii [TA] SYN: valve of coronary sinus. v. spiralis SYN: spiral fold of cystic duct. v. tricuspidalis SYN: tricuspid valve. v. venae cavae inferioris [TA] SYN: valve of inferior vena cava. v. venosa [TA] 1. in the embryo, one of the pair of valves at the opening from the sinus venosus into the right atrium; 2. [NA] SYN: venous valve. v. vestibuli obsolete term for v. venosa (1) .

valvular (val′vu-lar)
SYN: valvate.

valvule (val′vul) [TA]
A valve, especially one of small size. SYN: valvula [TA] . [L. valvula] Foltz v. SYN: Bochdalek valve. lymphatic v. [TA] one of the delicate semilunar valves found in lymphatic vessels; they are usually paired and similar in structure to venous valves and occur at close intervals along the vessel wall. SYN: valvula lymphatica [TA] .

valvulitis (val-vu-li′tis)
Inflammation of a valve, especially a heart valve. [Mod. L. valvula, valve, + G. -itis, inflammation] rheumatic v. v. characterized in the acute stage by small fibrin vegetations along the lines of closure and by Aschoff bodies in the cusps; in the chronic stage, it is characterized by scarring, commissural adhesion, and stenosis and/or regurgitation.

valvuloplasty (val′vu-lo-plas′te)
SYN: valvoplasty.

valvulotome (val′vu-lo-tom)
An instrument for sectioning a valve.

valvulotomy (val-vu-lot′o-me)
SYN: valvotomy (1) .

valyl (Val, V) (val′il)
The radical of valine.

Van, van
For some names with this prefix not found below, see the principal part of the name.

vanadate (van′a-dat)
A salt of vanadic acid.

vanadic acid (va-nad′ik)
An acid, H3VO4, derived from vanadium, forming salts with various bases.

vanadium (V) (va-na′de-um)
A metallic element, atomic no. 23, atomic wt. 50.9415; a bioelement, its deficiency can result in abnormal bone growth and a rise in cholesterol and triacylglycerol levels. [Vanadis, Scand. goddess] v. group those elements resembling v. in chemical and metallurgic properties; included with v. are niobium and tantalum.

van Bogaert
Ludo, 20th century Belgian neurologist. See Canavan-van Bogaert-Bertrand disease, van Bogaert encephalitis.

van Buchem
Francis Steven Peter, Dutch internist, *1897. See van Buchem syndrome.

van Buren
William H., U.S. surgeon, 1819–1883. See van Buren sound, van Buren disease.

vancomycin (van-ko-mi′sin)
An antibiotic isolated from cultures of Nocardia orientalis, bactericidal and bacteriostatic against Gram-positive organisms; available as the hydrochloride.

van Creveld
S., Dutch pediatrician, *1894. See Ellis-van Creveld syndrome.

vandal root (van′dal)
SYN: valerian.

van Deen
Izaak A., Dutch physiologist, 1804–1869. See van Deen test.

van den Bergh
A.A.H., Dutch physician, 1869–1943. See van den Bergh test.

van der Kolk
Jacobus L.C.S., Dutch physician, 1797–1862.

van der Spieghel
See Spigelius.

van der Velden
Reinhardt, German physician, 1851–1903. See van der Velden test.

van der Waals
Johannes D., Dutch physicist and Nobel laureate, 1837–1923. See van der Waals forces, under force.

van Ekenstein
W.A., 19th century scientist. See Lobry de Bruyn-van Ekenstein transformation.

van Ermengen
Emile P., Belgian bacteriologist, 1851–1932. See van Ermengen stain.

van Gieson
Ira, U.S. histologist and bacteriologist, 1865–1913. See van Gieson stain.

van Helmont
Jean B., Flemish physician and chemist, 1577–1644. See van Helmont mirror.

van Horne, Hoorne, Hoorn, Heurenius
Jan (Johannes), Dutch anatomist, 1621–1670. See van Horne canal.

vanilla (va-nil′a)
The cured, full-grown, unripe fruit of Vanila planifolia (Mexican or Bourbon v.) or of V. tahitensis (Tahiti v.), orchids (family Orchidaceae) native to Mexico and cultivated in other tropical countries; a flavoring agent. [Sp. vainilla, little pod]

vanillate (va-nil′at)
A compound of vanillic acid; C8H8O4.

vanillic acid (va-nil′ik)
A flavoring agent.

vanillin (va-nil′in)
Obtained from vanilla and also prepared synthetically; a flavoring agent; used to detect ornithine, sugar alcohols, phenols, and certain sterols.

vanillism (va-nil′izm)
1. Symptoms of irritation of the skin, nasal mucous membrane, and conjunctiva from which workers with vanilla sometimes suffer. 2. Infestation of the skin by sarcoptiform mites found in vanilla pods.

vanillylmandelic acid (VMA) (van′i-lil-man-del′ik, va-nil′il-)
Misnomer for 4-hydroxy-3-methoxymandelic acid (α,3-dihydroxy-2-methoxybenzeneacetic acid);the major urinary metabolite of adrenal and sympathetic catecholamines ( e.g., from both epinephrine and norepinephrine); elevated in most patients with pheochromocytoma.

Van Slyke
Donald D., U.S. biochemist, 1883–1971. See slyke, V. apparatus, V. formula.

van't Hoff
Jacobus H., Dutch chemist and Nobel laureate, 1852–1911. See van't Hoff equation, van't Hoff law, van't Hoff theory, Le Bel-van't Hoff rule.

vapor (va′per)
1. Molecules in the gaseous phase of a solid or liquid substance exposed to a gas. 2. A visible emanation of fine particles of a liquid. 3. A medicinal preparation to be administered by inhalation. [L. steam] anesthetic v. the gaseous phase of a liquid anesthetic with sufficient partial pressure at room temperature to produce general anesthesia when inhaled.

vaporization (va-por-i-za′shun)
1. The change of a solid or liquid to a state of vapor. 2. The therapeutic application of a vapor.

vaporize (va′-per-iz)
1. To convert a solid or liquid into a vapor. 2. To apply a vapor therapeutically.

vaporizer (va′per-iz-er)
1. An apparatus for reducing medicated liquids to a state of vapor suitable for inhalation or application to accessible mucous membranes. SEE ALSO: nebulizer, atomizer. 2. A device for volatizing liquid anesthetics. flow-over v. a device for vaporization of a liquid anesthetic by causing gases to pass over the anesthetic or over material saturated with the anesthetic. temperature-compensated v. a v. of liquid anesthetics with graduated settings calibrated to deliver a known constant concentration of a specific anesthetic despite changes in inflow volume and despite cooling brought about by vaporization.

vaporthorax (vap-er-tho′raks)
The existence of large water vapor bubbles in the pleural space between the lungs and the chest wall in an unprotected person exposed to altitudes above 63,000 ft., where the barometric pressure is less than 47 mm Hg and where water at body temperature vaporizes from the liquid state.

vapotherapy (va′po-thar′a-pe)
Treatment of disease by means of vapor or spray.

Va/Q
Abbreviation for ventilation/perfusion ratio.

Vaquez
Louis H., French physician, 1860–1936. See V. disease.

variability (var′e-a-bil′i-te)
1. The capability of being variable. 2. In genetics, the potential or actual differences, either quantitative or qualitative, in phenotype among individuals. baseline v. of fetal heart rate the beat-to-beat changes in fetal heart rate as recorded on a graph. beat-to-beat v. of fetal heart rate v. of fetal heart rate measured in changes in the QRS-QRS interval from heart beat to heart beat; measured with electronic internal fetal heart rate monitors.

variable (var′e-a-bl)
1. That which is inconstant, which can or does change, as contrasted with a constant. 2. Deviating from the type in structure, form, physiology, or behavior. [L. vario, to vary, change, differ] continuous v. a v. that may take on any value in an interval or intervals (its domain). continuous random v. continuous v. that may randomly assume any value in its domain but any particular value has no probability of occurring, only a probability density. dependent v. in experiments, a v. that is influenced by or dependent upon changes in the independent v.; e.g., the amount of a written passage retained (dependent v.) as a function of the different numbers of minutes (independent v.) allowed to study the passage. discrete v. a v. that may assume only a countable (usually finite) number of values. discrete random v. a random v. that may assume a countable number of values, each with a probability strictly greater than zero. independent v. a characteristic being measured or observed that is hypothesized to influence another event or manifestation (the dependent v.) within a defined area of relationships under study; that is, the independent v. is not influenced by the event or manifestation, but may cause it or contribute to its variation. See dependent v.. intermediate v. a v. in a causal pathway that causes variation in the dependent v. and is itself caused to vary by the independent v.. intervening v. an event, such as an attitude or emotion, inferred to occur within an organism between the stimulation and response in such a way as to influence or determine the response. mixed discrete-continuous random v. a random v. that may assume some values with probabilities and others with probability densities. For example, in a 35-year-old man with familial polyposis of the colon, the distribution of time until malignant disease occurs consists of a probability that he already has cancer (which would be assigned the waiting time 0), a probability density of developing it in the future, and a probability that he will die of some other cause before he develops cancer. moderator v. a v. that interacts by virtue of being antecedent or intermediate in the causal pathway. random v. a v. that may assume a set of values, each with fixed probabilities or probability densities (its distribution), in such a way that the total probability assigned to the distribution is unity; the random v. may be discrete, continuous, or mixed discrete-continuous.

variance (var′e-ans)
1. The state of being variable, different, divergent, or deviate; a degree of deviation. 2. A measure of the variation shown by a set of observations, defined as the sum of squares of deviations from the mean, divided by the number of degrees of freedom in the set of observations. ball v. swelling and changes in shape and consistency of the ball in a ball-valve prosthesis, especially in one replacing the aortic valve.

variant (var′e-ant)
1. That which, or one who, is variable. 2. Having the tendency to alter or change, exhibit variety or diversity, not conform with, or differ from the type. inherited albumin variants [MIM*103600] types of human serum albumin, distinguished by characteristic mobility patterns on electrophoresis; each type is due to a mutation of a gene controlling albumin synthesis; the mutant genes are codominant with the normal gene for albumin A, and the group forms a system of genetic polymorphism; types include: albumin b (slow), found occasionally in persons of European ancestry; albumin Ghent (fast), found first at Ghent, Belgium; albumin Mexico (slow), found in Indians of Mexico and the southwestern United States; albumin Naskapi (fast), found in the Naskapi and other Indians of northern North America; and albumin Reading (fast), found first at Reading, England. L-phase variants bacterial variants that do not have rigid cell walls but that may contain varying amounts of cell wall material; they are spherical to coccobacillary in shape and vary in size from small bodies that pass through filters which retain bacteria to bodies that are larger than the bacterial form; they are Gram-negative and resistant to penicillin. The variants differ greatly from the parent bacterial cells in mode of reproduction, physiology, growth requirements, and individual and colonial morphology; they are generally considered to be nonpathogenic, even if derived from a pathogenic bacterium. [L. fr. Lister Institute]

variate (var′e-at)
A measurable quantity capable of taking on a number of values; may be binary ( i.e., capable of taking on two values in a certain interval of values), continuous (i.e., capable of taking on all values in a certain interval of real values), or discrete ( i.e., capable of taking on a limited number of values in a certain interval of real values).




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