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

viscus
(vis´kәs) pl. vis´cera any large interior organ in any of the great body cavities, especially those in the abdomen.

vision
(vizh´әn) the faculty of seeing; its basic components are the eye itself, the visual areas in the brain, and the optic nerve that connects the two. The eye works like a camera; rays of light enter it through the adjustable iris and are focused by the lens onto the retina, a thin light-sensitive layer that corresponds to...

visiting nurse
community health nurse.

Vistaril
(vis´tә-ril) trademark for preparations of hydroxyzine, an antianxiety agent, antiemetic, sedative, and antipruritic.

visual agnosia
inability to recognize familiar objects by sight, usually due to a lesion in one of the visual association areas. Called also object blindness and psychic blindness.

visual angle
the angle between two lines passing from the edges of an object seen, through the nodal point of the eye, to the corresponding edges of the image of the object seen.

visual aphasia
alexia.

visual areas
three areas (first, second, and third visual areas) of the visual cortex. The first visual area is better known as the striate cortex.

visual axis
an imaginary line passing from the midpoint of the visual field to the fovea centralis. See illustration at optic axis.

visual cells
cells in the retina that act as photoreceptors; see rod (def. 2) and cone (def. 2).

visual cortex
the area of the occipital lobe of the cerebral cortex concerned with vision; the striate cortex is also called the first visual area, and the adjacent second and third visual areas serve as its association areas.

visual field
(F) (vf) the area within which stimuli will produce the sensation of sight with the eye in a straight-ahead position.

visual hallucination
a hallucination of sight.

visual line
a line from the point of vision of the retina to the object of vision; called also visual axis.

visual system
the series of structures by which visual sensations are received from the environment and conveyed as signals to the central nervous system; it consists of the photoreceptors in the retina and the afferent fibers in the optic nerve, chiasm, and tract.

visual zone
those dioptric surfaces and media around an optic axis in which there is practically no aberration of light rays.

visual-spatial agnosia
visuospatial agnosia lack of the ability to analyze and orient using visual representations and their spatial relationships.

visualization
(vizh″oo-әl-ĭ-za´shәn) the act of viewing or of achieving a complete visual impression of an object. use of a person's own imagination and positive thinking to reduce stress or promote healing.

visuoauditory
(vizh″oo-o-aw´dĭ-tor″e) pertaining to vision and hearing.

visuognosis
(vizh″oo-og-no´sis) recognition and interpretation of visual impressions.

visuolexic
(vizh″u-o-lek´sik) pertaining to the visual aspects of language, as in perception of written language.

visuopsychic
(vizh″oo-o-si´kik) visual and psychic; applied to the area of the cerebral cortex concerned in judgment of visual sensation.

visuosensory
(vizh″oo-o-sen´sә-re) pertaining to perception of visual impressions.

visuospatial
(vizh″oo-o-spa´shәl) pertaining to visual perception of spatial relationships.

vital
(vi´tәl) pertaining to life; necessary to life.

vital capacity
(VC) the greatest volume of gas that, following maximum inhalation, can be expelled during a complete, slow, forced exhalation; equal to inspiratory capacity plus expiratory reserve volume. See also pulmonary function tests.

vital point
a point in the medulla oblongata, at the respiratory center, puncture of which causes immediate death.

vital pulp
dental pulp whose blood supply and nerve supply are both intact, so that it is not necrotic. See also necrotic pulp.

vital signs
the signs of life, namely pulse, respiration, and (body) temperature.

vital stain
a stain introduced into the living organism, and taken up selectively by various tissue or cellular elements.

vital teeth
teeth that have vital pulp, with intact nerve and blood supplies.

Vitali test
(for alkaloids) evaporate with fuming nitric acid and add a drop of potassium hydroxide; color reactions will occur. For atropine the color is violet, turning to red. (for alkaloids) add sulfuric acid, potassium chlorate, and an alkaline sulfide; various color reactions will follow. (for bile pigment...

vitality
(vi-tal´ĭ-te) the condition of being alive, as opposed to death or necrosis. pulp vitality the normal condition of the dental pulp, having vascularity and sensation.

Vitallium
(vi-tal´e-әm) trademark for a cobalt-chromium alloy used for dentures and surgical appliances.

vitamer
(vi´tә-mәr) one of multiple related chemical compounds possessing a given vitamin activity.

vitamin
(vi´tә-min) any of a group of organic substances found in foods and essential in small quantities for growth, health, and the preservation of life itself. The body needs vitamins just as it requires other food constituents such as proteins, fats, carbohydrates, minerals, and water. The absence of one or more vitam...

vitamin A
a fat-soluble vitamin that helps to maintain epithelial tissues that cover the body and line certain internal organs. It is also essential for proper growth of skeletal and soft tissues, and is necessary for light-sensitive retinal pigments in the eye that make night vision possible. The particular manifestation of vitamin A de...

vitamin B complex
a group that was originally called “vitamin B,” but was later found to contain numerous different vitamins. They are still referred to as a group because they are often found together in foods. Deficiency in only one of them is rare, so that a deficiency of one B vitamin usually is complicated by deficiencies ...

vitamin B1
thiamine, a member of the vitamin B complex that is necessary to break down and release energy from carbohydrates. Lack of this vitamin can cause loss of appetite, certain types of neuritis, and, in severe cases, beriberi, a condition that affects the brain, heart, and nerves. The best food sources for this vitamin are yeasts, ham an...

vitamin B12
cyanocobalamin, a member of the vitamin B complex that contains cobalt and is needed for the efficient production of red blood cells and for the health of the nervous system; its activity is associated with that of another B vitamin, folic acid. Inability to absorb vitamin B12 occurs in pernicious anemia and sprue. Vitamin B12 is not...

vitamin B2
riboflavin, a member of the vitamin B complex that functions as a coenzyme concerned with oxidative processes; it is a component of flavin adenine dinucleotide and flavin mononucleotide, coenzymes that are prosthetic groups for flavoproteins.

vitamin B6
any of a group of water-soluble members of the vitamin B complex, including pyridoxine, pyridoxal, and pyridoxamine; in the body they are concerned in the metabolism of amino acids, the degradation of tryptophan, and the metabolism of glycogen. They are found in many foods, especially meats, liver, vegetables, whole grains, cereals, ...

vitamin C
ascorbic acid, a substance necessary for the health of supporting tissues such as bone, cartilage, and connective tissue; deficiency causes scurvy. Vitamin C is found in fresh fruits and vegetables, including citrus fruits, tomatoes, brussels sprouts, and to some extent whole potatoes. Cooking and storage destroy much of ...

vitamin D
term used for either of two active substances required for the body to use calcium and phosphorus, two elements that are essential for the growth and maintenance of bone. Ergocalciferol is sometimes called vitamin D2, and cholecalciferol is sometimes called vitamin D3. The action of sunlight on the skin changes certain substances n t...

vitamin D–resistant rickets
a condition almost identical clinically to ordinary rickets, but not responsive to administration of large doses of vitamin D; it is often hereditary, but sometimes may be acquired. In hypophosphatemic vitamin D–resistant rickets, low serum concentration of phosphate is the main characteristic, while in hypocalcemic vitamin D&#...

vitamin deficiency
a condition caused by inadequate amounts of any of the vitamins in the diet.

vitamin E
a vitamin that has been discovered to be a group containing at least eight different antioxidants; the most common is alpha tocopherol. The vitamins in this group prevent the oxidation of unsaturated fatty acids, thus preventing cell damage that can lead to neurological symptoms. Vitamin E is found in wheat germ oil, cereals, egg yol...

vitamin K
any of a group of substances, including vitamin K1 (phytonadione) and vitamin K2 (menaquinone), which promote blood clotting by increasing the synthesis of prothrombin by the liver. Deficiency of vitamin K delays clotting of the blood, with excessive bleeding and bruises under the skin. Food sources are alfalfa, spinach, cabbage, put...

vitamin test
see specific tests, including dark-adaptation test, deoxyuridine suppression test, Friderichsen test, histidine loading test, and Schilling test.

vitelline
(vĭ-tel´ēn) resembling or pertaining to the yolk of an egg or ovum.

vitelline membrane
the cytoplasmic, noncellular membrane surrounding an oocyte.

vitelline veins
veins that return the blood from the yolk sac to the primordial heart of the early embryo.

vitellus
(vi-tel´әs) yolk.

vitiligo
(vit″ĭ-li´go) a type of hypomelanosis caused by destruction of melanocytes, resulting in small or large patches of depigmentation that may have darkened borders and may slowly enlarge. The etiology is unknown; some cases seem to have a hereditary component and others may be part of an autoimmune disease. adj....

vitrectomy
(vĭ-trek´tә-me) surgical removal of a diseased vitreous body, such as in a person with diabetic retinopathy, glaucoma, or certain other eye conditions.

vitreitis
(vit″re-i´tis) hyalitis.

vitreous
(vit´re-әs) glasslike or hyaline. vitreous body.

vitreous abscess
an abscess of the vitreous humor, resulting from infection, trauma, or foreign body.

vitreous body
the transparent gel filling the inner portion of the eyeball between the lens and retina. Called also vitreous and vitreous humor.

vitreous chamber
the space in the eyeball that contains the vitreous body; it is bounded anteriorly by the lens and ciliary body and posteriorly by the posterior wall of the eyeball.

vitreous membrane
Descemet membrane. hyaline membrane (def. 1). Bruch membrane. a delicate boundary layer investing the vitreous body.

vitritis
(vĭ-tri´tis) hyalitis.

vitronectin
(vit″ro-nek´tin) a multifunctional adhesive glycoprotein found in serum and various tissues. Its functions include regulation of the coagulation, fibrinolytic, and complement cascades, and it plays a role in hemostasis, wound healing, tissue remodeling, and cancer. It mediates the inflammatory and repair reactions...

viviparous
(vi-vip´ә-rәs) giving birth to living young which develop within the maternal body.

Vladimiroff operation
Mikulicz operation (def. 3).

VLBW
very low birth weight; see very low birth weight infant.

VLDL
very-low-density lipoprotein.

VM-26
teniposide.

VMD
Veterina´riae Medici´nae Doc´tor (Doctor of Veterinary Medicine).

vocal
(vo´kәl) pertaining to the voice.

vocal area
rima glottidis.

vocal cord paralysis
vocal fold paralysis paralysis of one or both or the vocal cords; the voice is weakened but not lost. See also laryngeal paralysis. Called also phonetic paralysis.

vocal cords
the thin, reedlike folds of mucous membrane in the larynx, consisting of an upper pair called the false vocal cords and a lower pair called the true vocal cords. They vibrate to make vocal sounds during speech and can produce a wide range of sounds. Each cord has one end attached to the front wall of the larynx, close to that of the ...

vocal folds
true vocal cords.

vocal ligament
the elastic tissue membrane extending from the thyroid cartilage in front to the vocal process of the arytenoid cartilage behind.

vocal nodules
vocal cord nodules small white nodules appearing on the vocal cords in chorditis tuberosa with excessive use of the voice; called also singer's nodes or nodules and teacher's nodes or nodules.

vocal resonance
(VR) the sound of ordinary speech as heard through the chest wall.

vocal tract
the passages from the glottis through the nose and throat that influence the quality of the voice.

vocalis muscle
vocal muscle: one of the intrinsic muscles of the larynx; origin, angle between laminae of thyroid cartilage; insertion, vocal process of arytenoid cartilage; innervation, recurrent laryngeal nerve; action, shortens and relaxes vocal folds.

Vogel and Lee test
(for mercury) add 3 per cent of hydrochloric acid and concentrate the urine to one fifth its original volume. Add a piece of clean copper wire. A silvery film indicates mercury. To confirm, place the wire in a tube with a plug of gold foil and distill the mercury over onto the gold. Sublime a crystal of iodine onto the me...

Voges-Proskauer test
(for differentiation of Enterobacteriaceae) a test for the production of acetylmethylcarbinol from glucose in bacterial cultures. An appropriate culture is treated with a solution of potassium hydroxide and creatine. Development of a red color indicates a positive reaction. Enterobacter, Klebsiella, Pantoea, and Serratia are V-...

Vogt point
Vogt-Hueter point a point at the intersection of a horizontal line two fingerbreadths above the zygoma with a vertical line a thumb-breadth behind the ascending sphenofrontal process; here trephination may be performed in traumatic meningeal hemorrhage.

Vogt syndrome
(fōkt) a syndrome associated with birth trauma, characterized by bilateral athetosis, walking difficulties, spasmodic outbursts of laughing or crying, speech disorders, excessive myelination of the nerve fibers of the corpus striatum, giving it a marbled appearance (status marmoratus), and sometimes mental de...

Vogt-Koyanagi syndrome
(fōkt´ ko-yah-nah´ge) uveomeningitis characterized by exudative iridocyclitis and choroiditis associated with patchy depigmentation of the skin and hair; the lashes and eyebrows also become whitened, and there may also be retinal detachment and associated deafness and tinnitus. Cf. Vogt-Koyanagi-Harada syndro...

Vogt-Koyanagi-Harada syndrome
(fōkt´ ko-yah-nah´ge hah-rah´dah) a syndrome of uveomeningitis with retinochoroidal detachment, temporary or permanent deafness and blindness, and sometimes (usually not permanent) alopecia, vitiligo, and poliosis. The etiology is unknown, but it may be an inflammatory autoimmune condition. Called also Harada syndrome.

Vogt-Spielmeyer disease
(fōkt´ shpēl´mi-er) the juvenile form of neuronal ceroid-lipofuscinosis, with onset between 5 and 10 years of age, characterized by rapid cerebroretinal degeneration, massive loss of brain substance, excessive neuronal storage of lipofuscin, and death within 10 to 15 years.

Vohwinkel syndrome
(fo-ving´kәl) an autosomal dominant, progressive, dystrophic form of palmoplantar keratoderma beginning in childhood, sometimes with scarring alopecia and deafness.

voice
(vois) the sound produced by the speech organs and uttered by the mouth.

voice sounds
auscultatory sounds heard over the lungs or airways when the patient speaks; increased resonance indicates consolidation or effusion. Types include bronchophony, egophony, laryngophony, and tracheophony.

void
(void) excrete.

voiding pressure study
simultaneous measurement of bladder contraction, urinary flow, and sphincter electromyogram.

vol
volume.

vola
(vo´lә) a concave or hollow surface. vola manus palm. vola pedis planta pedis.

volar
(vo´lәr) pertaining to the sole or palm; indicating the flexor surface of the forearm, wrist, or hand.

volaris
(vo-lar´is) palmar.

volatile
(vol´ә-til) evaporating rapidly; vaporizing readily at low temperatures.

volatile oil of mustard
a volatile oil distilled from the seeds of black mustard (Brassica nigra); it consists predominantly of the chemical allyl isothiocyanate and is used as a strong counterirritant and rubefacient.

volatilization
(vol″ә-til″ĭ-za´shәn) conversion into a vapor or gas without chemical change.

volition
(vo-lish´әn) the act or power of willing. adj., voli´tional, adj. .

volitional tremor
action tremor.