Bma Illustrated Medical Dictionary

vitamins are used to treat certain disor-

ders. For example, vitamin D is used to

treat osteomalacia, and vitamin A deri-

vatives are given for severe acne.

vitiligoA common disorder of skinpig-

mentation in which patches of skin,

most commonly on the face, hands,

armpits, and groin, lose their colour.

Vitiligo is thought to be an autoimmune

disorder. It may occur at any age but

usually develops in early adulthood.

Spontaneous repigmentation occurs

in some cases. A course of phototherapy

using PUVAcan also induce repigmen-

tation of the skin, and creams containing

corticosteroid drugsmay help.

vitreous haemorrhageBleeding into

the vitreous humour. A common cause

is diabetic retinopathy. Vitreous haem-

orrhage often affects vision; a major

haemorrhage causes poor vision until

the blood is reabsorbed, which may not

be for several months, if at all.

vitreous humourThe transparent, gel-

like body that fills the rear compartment

of the eyebetween the crystalline lens

and the retina. The vitreous humour

consists almost entirely of water.

vivisectionThe performance of a sur-

gical operation on a live animal,

particularly for research purposes. (See

also animal experimentation.)

vocal cordsTwo fibrous sheets of tis-

sue in the larynxthat are responsible

for voice production. The vocal cords

VOCAL CORDS

are attached at the front to the thyroid

cartilage and at the rear to the aryten-

oid cartilages. To produce sound, the

vocal cords, which normally form a V-

shaped opening, close and vibrate as

air expelled from the lungs passes

between them. Alterations in cord ten-

sion produce sounds of different pitch,

which are modified by the tongue,

mouth, and lips to form speech.

voice-boxSee larynx.

voice, loss ofInability to speak norm-

ally. Temporary partial loss of voice

commonly results from straining of the

muscles of the larynxthrough overuse

of the voice or from inflammation of the

vocal cords in laryngitis. Persistent or

recurrent voice loss may be due to

polypson the vocal cords, thickening of

the cords in hypothyroidism, or inter-

ference with the nerve supply to the

larynx muscles due to cancer of the lar-

ynx, thyroid gland, or oesophagus. Total

loss of voice is rare and is usually of

psychological origin. (See also hoarse-

ness; larynx, disorders of.)

Volkmann’s contractureA disorder

in which the wrist and fingers become

permanently fixed in a bent position. It

occurs because of an inadequate blood

supply to the forearm muscles that con-

trol the wrist and fingers as a result of

an injury. Initially, the fingers become

cold, numb, and white or blue. Finger

movements are weak and painful, and

there is no pulse at the wrist. Unless

treatment is started within a few hours,

wrist and finger deformity develops.

Treatment is by manipulation back

into position of any displaced bones,

followed, if necessary, by surgical res-

toration of blood flow in the forearm. If

there is permanent deformity, physio-

therapymay help to restore function.

volvulusTwisting of a loop of intestine

or, in rare cases, of the stomach. Volvu-

lus is a serious condition that causes

obstruction of the passage of intestinal

contents (see intestine, obstruction of)

and a risk of strangulation. If strangula-

tion occurs, blockage of blood flow to

the affected area leads to potentially

fatal gangrene. The symptoms of volvu-

lus are severe episodes of abdominal

pain followed by vomiting.Volvulus may

VITILIGO VOLVULUS

V

Arytenoid cartilages

Vocal cords

Trachea

Cut edge of

thyroid cartilage

LOCATION SIDE VIEW OF LARYNX

Ligament

Larynx