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Medical Dictionary - Dictionary of Medicine and Human Biology


Medical Dictionary


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watershed
1. The area of marginal blood flow at the extreme periphery of a vascular bed. 2. Slopes in the abdominal cavity, formed by projections of the lumbar vertebrae and the pelvic brim that determine the direction in which a free effusion will gravitate when the body is in a supine position.

Waterston
David J., British thoracic and pediatric surgeon, *1910. See W. operation, W. shunt.

Watson
Cecil J., U.S. physician, 1901–1983. See W.-Schwartz test.

Watson
James Dewey, U.S. geneticist and Nobel laureate, *1928. See W.-Crick helix.

watt (W) (waht)
The SI unit of electrical power; the power available when the current is 1 ampere and the electromotive force is 1 volt; equal to 1 joule (107 ergs) per second or 1 voltampere. [James W., Scot. engineer, 1736–1819]

wave (wav)
    A movement of particles in an elastic body, whether solid or fluid, whereby an advancing series of alternate elevations and depressions, or rarefactions and condensations, is produced.

    The elevation of the pulse, felt by the finger, or represented in the curved line of the sphygmograph. 3. The complete cycle of changes in the level of a source of energy that is repetitively varying with respect to time; in the electrocardiogram and the electroencephalogram, the wave is essentially a voltage-time graph. SEE ALSO: rhythm. [A.S. wafian, to fluctuate]

    A wave:
    • the initial negative deflection in the electroretinogram, presumably reflecting retinal photoreceptor activity
    • an atrial deflection in an electrogram recorded from within the atrium of the hear
    • the first positive deflection of the atrial and venous pulses due to atrial systole.


    acid wave: acid tide.

    alkaline wave: alkaline tide.

    alpha wave: alpha rhythm.

    arterial wave: a wave in the jugular phlebogram due to transmission of carotid artery pulsation.

    B wave: the initial positive deflection in the electroretinogram, possibly arising from the inner nuclear layer of the retina.

    beta wave: beta rhythm.

    brain wave: colloquialism for electroencephalogram.

    C wave:
    • a monophasic positive deflection in the electroretinogram arising in the pigment epithelium of the retina.
    • wave in the venous and atrial pulses occurring during isovolumic ventricular contraction in which the closed atrioventricular valves (mitral and tricuspid) are abruptly displaced into the atria with creation of a pressure transient.


    cannon wave: an exaggerated A wave in the jugular pulse caused by right atrial contraction occurring after ventricular contraction has closed the tricuspid valve, as in ventricular premature beats and in complete A-V block.

    D wave: a positive or negative deflection in the electroretinogram occurring when a light stimulus is removed (off-response).

    delta wave: a premature upstroke of the QRS complex due to an atrial ventricular bypass tract as in WPW syndrome.

    dicrotic wave: the second rise in the tracing of a dicrotic pulse. SYN: recoil wave.

    electrocardiographic wave: a deflection of special shape and extent in the electrocardiogram representing the electric activity of a portion of the heart muscle.

    epsilon wave: late R wave (in lead V1) of delayed right ventricular activation in arrhythmogenic RV dysplasia.

    excitation wave: a wave of altered electrical conditions that is propagated along a muscle fiber preparatory to its contraction.

    F waves: the waves of atrial flutter usually best seen in ECG leads 2, 3, and AVF. (A small f indicates atrial fibrillation).

    f wave, ff waves: atrial fibrillation wave. SYN: fibrillary waves, fibrillatory waves, flutter-fibrillation waves.

    fibrillary waves: f wave.

    fibrillatory waves: f wave.

    flat top waves: activity in the electroencephalogram having a pattern suggesting a flat top; these waves are often found in temporal lobe discharges.

    fluid wave: a sign of free fluid in the abdominal cavity; percussion on one side of the abdomen transmits a wave that is felt on the opposite side.

    flutter-fibrillation waves: f wave.

    microelectric waves: microwaves.

    mucosal wave: the movement of the mucous membrane of the vocal cord during phonation.

    overflow wave: the descending wave of the sphygmogram from the apex to the first anacrotic break.

    P wave: the first complex of the electrocardiogram, during sinus and atrial rhythms, representing depolarization of the atria; if the P wave is retrograde or ectopic in axis or form, it is labeled P′.

    percussion wave: wave the main positive wave of an arterial pulse tracing.

    postextrasystolic T wave: the modified T wave of the beat immediately following an extrasystole.

    pulse wave: the progressive expansion of the arteries occurring with each contraction of the left ventricle of the heart.

    Q wave: the initial deflection of the QRS complex when such deflection is negative (downward).

    R wave: the first positive (upward) deflection of the QRS complex in the electrocardiogram; successive upward deflections within the same QRS complex are labeled R′, R′′, etc.

    random waves: waves in the electroencephalogram which occur paroxysmally and asynchronously.

    recoil wave: dicrotic wave.

    retrograde P wave: the P wave pattern in the electrocardiogram representing retrograde depolarization of the atria, the impulse spreading from the AV junction or the lower atrium upward.

    S wave: a negative (downward) deflection of the QRS complex following an R w; successive downward deflections within the same QRS complex are labeled S′, S′′, etc.

    sonic waves: audible sound waves, as distinguished from ultrasonic waves.

    supersonic waves: sound waves of higher frequency than the level of audibility.

    T wave: the next deflection in the electrocardiogram following the QRS complex; represents ventricular repolarization.

    theta wave: theta rhythm.

    tidal wave: the wave between the percussion wave and the dicrotic wave in the downward limb of the arterial pulse tracing.

    Traube-Hering waves: Traube-Hering curves, under curve.

    U wave: a positive wave following an upright T wave of the electrocardiogram. It is negative following an inverted T wave.

    ultrasonic waves: the periodic configuration of energy produced by sound having a frequency greater than 30,000 Hz.

    V wave: a large pressure wave visible in recordings from either atrium or its incoming veins, normally produced by venous return but apparently becoming very large when blood regurgitates through the AV valve beyond the chamber from which the recording is made. This regurgitant wave is not a true V wave, which is a passive (filling) wave.

    x wave: the negative wave in the atrial and venous pulse curves produced when ventricular ejection moves the floors of the atria toward the ventricular apices.

    y wave: the negative wave in the atrial and venous pulse curves reflecting rapid filling of the ventricles just after the atrioventricular valves open.
waveform
The form of a pulse; e.g., an arterial pressure or displacement wave; or of the pacemaker pulse as demonstrated on the oscilloscope under a specified load. pressure w. a graphic representation of intravascular or intracardiac pressure related to phases of the cardiac cycle, displayed on an oscilloscope monitor or paper copy.

wavelength (Λ) (wav′length)
The distance from one point on a wave (frequently shaped like a sine curve) to the next point in the same phase; i.e., from peak to peak or from trough to trough.

wavenumber (σ) (wav′num-ber)
The number of waves per centimeter (cm−1), used to simplify the large and unwieldy numbers heretofore used to designate frequency.

waveshape (wav′shap)
SYN: wave form.

wax (waks)
    A thick, tenacious substance, plastic at room temperature, secreted by bees for building the cells of their honeycomb. SYN: beeswax, cera.

    Any substance with physical properties similar to those of beeswax, of animal, vegetable, or mineral origin (oils, lipids, or fats that are solids at room temperature).

    Esters of high molecular weight fatty acids with monohydric or dihydric alcohols (aliphatic or cyclic), that are solid at room temperature. Often accompanied by free fatty acids. [A.S. weax]

    animal wax: beeswax, spermaceti, and any wax derived from the animal kingdom.

    baseplate wax: a hard pink wax used in dentistry for making occlusion rims.

    bleached wax: white wax.

    bone wax: a mixture of antiseptic agents, oil, and wax used to stop bleeding by plugging bone cavities or haversian canals. SYN: Horsley bone wax.

    boxing wax: wax used for boxing impressions. SEE ALSO: boxing.

    Brazil wax: carnauba wax.

    carnauba wax: a wax obtained from the Brazilian wax palm, Copernica cerifera; used in pharmaceuticals to coat medicaments in sustained release preparations and surfaces of tablets; used in waxes for wood and metal. SYN: Brazil wax, palm wax.

    casting wax: any soft solid wax used in dentistry for patterns of all types and for many other purposes; most are basically paraffin but are modified by addition of gum dammar, carnauba wax, or other ingredients, to meet various requirements. SYN: inlay wax.

    Chinese wax:
    • a vegetable wax
    • a wax secreted by a scale insect, Coccus ceriferus or C. pela, and deposited in the twigs of a species of ash tree; used in China to make candles and also medicinally.


    ear wax: cerumen.

    earth wax: ceresin.

    emulsifying wax: a washable ointment base consisting of a mixture of cetostearyl alcohol, sodium lauryl sulfate, and water.

    grave wax: adipocere.

    Horsley bone wax: bone wax.

    inlay wax: casting wax.

    Japan wax: a vegetable wax derived from Rhus succedanea and Toxicodendron verniciferum.

    mineral wax:
    • paraffin wax.
    • ceresin.
    • a mineral substance whose physical properties are similar to wax.


    montan wax: a mineral wax extracted from lignite. [L. montanus, of a mountain, fr. mons, mountain]

    palm wax: carnauba wax.

    paraffin wax: a wax derived from petroleum. SYN: mineral wax (1) .

    vegetable wax: palm wax or any wax derived from plants such as the bayberry.

    white wa:x yellow wax bleached by being rolled very thin and exposed to the light and air, or bleached by chemical oxidants; same uses as yellow wax. SYN: bleached wax, white beeswax.

    wool wax: adeps lanae.

    yellow wax: a yellowish, solid, brittle substance prepared from the honeycomb of the bee, Apis mellifera; the chief constituent is myricin (myricyl palmitate); others are cerotic acid (cerin), melissic acid, heptacosane, and hentriacontane; used in the preparation of ointments, cerates, plasters, and suppositories.
waxing, waxing-up (wak′sing)
The contouring of a pattern in wax, generally applied to the shaping in wax of the contours of a trial denture or a crown prior to casting in metal.

Wb
Symbol for weber.

WBC
Abbreviation for white blood cell.

weakness (wek′nes)
1. Lack of strength or potency. 2. Inability to perform normally. directional w. a right or left decrement of nystagmus, calculated from the responses to the binaural, bithermal caloric test.

wean (wen)
To implement weaning. [A.S. wenian]

weaning (wen′ing)
1. Permanent deprivation of breast milk and commencement of nourishment with other food. 2. Gradual withdrawal of a patient from dependency on a life support system or other form of therapy.

weanling (wen′ling)
A young animal that has become adjusted to food other than its mother's milk.

wear (war)
Wasting or deterioration caused by friction. occlusal w. attritional loss of substance on opposing occlusal units or surfaces. SEE ALSO: abrasion (3) .

web (web)
A tissue or membrane bridging a space. SEE ALSO: tela. [A.S.] esophageal w. a cribriform or w. formation in the esophagus caused by an irregular atrophy. w. of fingers/toes one of the folds of skin, or rudimentary w., between the fingers and toes. SYN: interdigital folds, plica interdigitalis. laryngeal w. congenital anomaly consisting of mucous membrane–covered connective tissue between the vocal cords located ventrally and extending dorsally for varying distances; it causes airway obstruction and hoarse cry in the newborn. terminal w. a network of actin filaments in the apical end of columnar epithelial cells that anchor in the zonula adherens.

webbing (web′ing)
Congenital condition apparent when adjacent structures are joined by a broad band of tissue not normally present to such a degree.

Weber
Rainer, 20th century U.S. pathologist. See W. stain.

Weber
Ernst Heinrich, German physiologist and anatomist, 1795–1878. See W. glands, under gland, W. law, W. paradox, W. test for hearing, Fechner-W. law, W.-Fechner law.

Weber
Frederick Parkes, English physician, 1863–1962. See W.-Christian disease, W.-Cockayne syndrome, Rendu-Osler-W. syndrome, Sturge-Kalischer-W. syndrome, Sturge-W. disease, Sturge-W. syndrome, Klippel-Trenaunay-W. syndrome.

Weber
Moritz Ignaz, German anatomist, 1795–1875. See W. organ.

Weber
Sir Hermann, English physician, 1823–1918. See W. sign, W. syndrome.

Weber
Wilhelm E., German physicist, 1804–1891. See W. point, W. triangle.

weber (Wb) (web′er)
SI unit of magnetic flux, equal to volt-seconds (V&chmpnt;s). [Wilhelm E. W., 1804–1891]

WEBINO
Acronym for wall-eyed bilateral internuclear ophthalmoplegia.

Webster
John, English chemist, 1878–1927. See W. test.

Webster
John C., U.S. gynecologist, 1863–1950.

Wechsler
David, U.S. psychologist, *1896. See W. intelligence scales, under scale, W.-Bellevue scale.

weddellite (hwed′del-ite)
A dihydrate of calcium oxalate; found in renal calculi. Cf.:whewellite. [for Weddell Sea, after James Weddell, Eng. navigator (1787–1834), + -ite]

Wedensky, Vvedenskii
Nikolai I., Russian neurophysiologist, 1852–1922. See W. effect, W. facilitation, W. inhibition.

wedge (wej)
A solid body having the shape of an acute-angled triangular prism. [A.S. weeg] dental w. a double inclined plane used for separating the teeth, maintaining the separation once obtained, or holding a matrix in place.

WEE
Abbreviation for western equine encephalomyelitis.

Weeks
John E., U.S. ophthalmologist, 1853–1949. See W. bacillus, Koch-W. bacillus.

Weeksella (wek-sel′a)
A genus of nonoxidative, aerobic Gram-negative rods. W. zoohelcum a bacterium producing infections in bites or scratches by dogs or cats.

Wegener
Friedrich, German pathologist, 1907–1990. See W. granulomatosis.

Wegner
Friedrich R.G., German pathologist, 1843–1917. See W. disease, W. line.

Weibel
Ewald R., Swiss physician, *1929. See W.-Palade bodies, under body.

Weichselbaum
Anton, Austrian pathologist, 1845–1920. See W. coccus.

Weidel
Hugo, Austrian chemist, 1849–1899. See W. reaction.

Weigert
Carl, German pathologist, 1845–1904. See W. law, W. iodine solution. See entries under stain.

weight (wat)
The product of the force of gravity, defined internationally as 9.80665 m/s2, times the mass of the body. [A.S. gewiht]
    apothecaries weight:
    an obsolescent system of weights based upon the weight of a grain of wheat. Has been used for centuries in weighing medicines and precious metals (Troy measure). Some drugs which have been available for long periods are still often designated as grains ( e.g., 5 grains of aspirin, 1/2 grain of codeine, 1/100 grain nitroglycerin). This weight system has been largely superseded by the metric system (based on grams). One grain is the equivalent of 64.8 milligrams. One scruple contains 20 grains; one dram contains 60 grains; one apothecary ounce contains 8 drams (480 grains); one apothecary pound contains 12 ounces (5760 grains).

    atomic weight (at. wt., AW):
    the mass in grams of 1 mol (6.02 × 1023 atoms) of an atomic species; the mass of an atom of a chemical element in relation to the mass of an atom of carbon-12 (12C), which is set equal to 12.000, thus a ratio and therefore dimensionless (although the actual mass, numerically the same, is sometimes expressed in daltons); not necessarily the weight of any individual atom of an element, since most elements are made up of several isotopes of different masses; e.g., the atomic weight of chlorine is 35.4527, because it is composed of 35Cl and 37Cl in proportions that give an average of 35.4527. SEE ALSO: molecular weight.

    birth weight in humans:
    the first weight of an infant obtained within less than the first 60 completed minutes after birth; a full-size infant is one weighing 2500 g or more; a low birth weight is less than 2500 g.; very low birth weight is less than 1500 g.; and extremely low is less than 1000 g.

    combining weight:
    gram equivalent.

    dry weight:
    the weight of material remaining after removing the water ( E.G., after heating above 100°C).

    equivalent weight:
    gram equivalent.

    gram-atomic weight:
    atomic weight expressed in grams. Cf.:mole.

    gram-molecular weight:
    molecular weight expressed in grams. Cf.:mole.

    molecular weight (mol wt, MW):
    the sum of the atomic weights of all the atoms constituting a molecule; the mass of a molecule relative to the mass of a standard atom, now 12C (taken as 12.000). Relative molecular mass (Mr) is the mass relative to the dalton and has no units. SEE ALSO: atomic weight. SYN: molecular mass, molecular weight ratio, relative molecular mass.
weightlessness (wat′les-nes)
The psychophysiologic effect of zero gravity, as experienced by someone falling freely in a vacuum ( e.g., astronauts in a stable orbit). A temporary state of simulated w. can be achieved during powered flight within the earth's atmosphere by traversing an inverted parabolic curve where gravitational pull and centrifugal force cancel each other out.

Weil
Adolf, German physician, 1848–1916. See W. disease.

Weil
Edmund, Austrian physician, 1880–1922. See W.-Felix reaction, W.-Felix test.

Weil
Ludwig A., German dentist, 1849–1895. See W. basal layer, W. basal zone.

Weill
Georges J., French ophthalmologist, 1866–1952. See W.-Marchesani syndrome.

Weill
Jean A., French physician, *1903. See Leri-W. disease, Leri-W. syndrome.

Weinberg
Wilhelm, German physician, 1862–1937. See Hardy-W. equilibrium, Hardy-W. law.

Weinberg
Michel, French pathologist, 1868–1940. See W. reaction.

Weingrow reflex
See under reflex.

Weir Mitchell
Silas, U.S. neurologist, poet, and novelist, 1829–1914. See Mitchell treatment, Gerhardt-Mitchell disease, W. treatment.

Weisbach
Albin, Austrian anthropologist, 1837–1914. See W. angle.

Weismann
August Friedrich Leopold, German biologist, 1834–1914. See weismannism.

weismannism (vis′man-izm)
Theory of the noninheritance of acquired characteristics.

Weiss
Nathan, Austrian physician, 1851–1883. See W. sign.

Weiss
Soma, U.S. physician, 1898–1942. See Charcot-W.-Baker syndrome, Mallory-W. lesion, Mallory-W. syndrome, Mallory-W. tear.

Weitbrecht
Josias, German-Russian anatomist in St. Petersburg, 1702–1747. See W. cartilage, W. cord, W. fibers, under fiber, W. foramen, W. ligament, apparatus ligamentosus weitbrechti.

Welander
Lisa, Swedish neurologist, *1909. See Kugelberg-W. disease, Wohlfart-Kugelberg-W. disease.

Welch
William H., U.S. pathologist, 1850–1934. See W. bacillus.

Welcker
Hermann, German anthropologist and anatomist, 1822–1898. See W. angle.

wellness (wel′nes)
A philosophy of life and personal hygiene that views health as not merely the absence of illness but the fullest realization of one's physical and mental potential, as achieved through positive attitudes, fitness training, a diet low in fat and high in fiber, and the avoidance of unhealthful practices (smoking, drug and alcohol abuse, overeating).W. programs are widely offered by employers, health insurance programs, and social service agencies. Formal programs typically include preventive measures (e.g., immunizations against pneumococcal pneumonia and influenza in the elderly) and surveillance for common diseases (e.g., hypertension, diabetes mellitus, and breast and colon cancer). Such programs tend to attract persons already attuned to healthful attitudes and practices. Little clinical evidence exists to support their usefulness or justify their expense.

Wells
G.C., 20th century British dermatologist. See W. syndrome.

Wells
Michael Vernon, 20th century English physician. See Muckle-W. syndrome.

welt (welt)
SYN: wheal. [O.E. waelt]




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