VITILIGO
VOLVULUS
V
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.
vitiligo A common disorder of
skin
pig-
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
PUVA
can also induce repigmen-
tation of the skin, and creams containing
corticosteroid drugs
may help.
vitreous haemorrhage Bleeding 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 humour The transparent, gel-
like body that fills the rear compartment
of the
eye
between the crystalline lens
and the retina. The vitreous humour
consists almost entirely of water.
vivisection The performance of a sur-
gical
operation
on
a
live
animal,
particularly for research purposes. (See
also
animal experimentation.)
vocal cords Two fibrous sheets of tis-
sue in the
larynx
that are responsible
for voice production. The vocal cords
VOCAL CORDS
LOCATION
SIDE VIEW OF LARYNX
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-box See
larynx.
voice, loss of Inability to speak norm-
ally. Temporary partial loss of voice
commonly results from straining of the
muscles of the
larynx
through overuse
of the voice or from inflammation of the
vocal cords
in
laryngitis.
Persistent or
recurrent voice loss may be due to
polyps
on 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 contracture A 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-
therapy
may help to restore function,
volvulus Twisting 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
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