CARPOPEDAL SPASM
Alternatively, the ligament may be cut
surgically in order to relieve pressure
on the nerve.
carpopedal spasm
Involuntary contraction of muscles in
the hands and feet. Carpopedal spasm is
due to low levels of calcium in the
blood. This problem, in turn, may be
caused by
hyperventilation
(abnormally
rapid breathing) or by disorders such
as
hypoparathyroidism
.
carpus
The eight bones of the
wrist
.
carrier
A person who is able to pass on an
infectious or inherited disease without
actually suffering from it themselves.
car sickness
See
motion sickness
.
cartilage
A type of
connective tissue
(a material
that holds body structures together)
made up of varying amounts of the
gel-like substance
collagen
.
Cartilage is
not as hard as
bone,
but it nevertheless
forms an important structural compo-
nent of various parts of the skeletal
system, including the
joints
.
Much of
the fetal skeleton is formed entirely of
cartilage. During childhood, the carti-
lage is gradually converted to bone by a
process known as
ossification
.
TYPES
There are three main types of cartilage:
hyaline
cartilage,
fibrocartilage,
and
elastic cartilage. Each type is composed
of a different proportion of collagen
and has a particular function.
Hyaline cartilage is a tough, smooth
tissue that lines the surfaces of joints,
such as the knee, providing an almost
frictionless layer over the bony parts of
the joint. If the lining becomes worn
(as occurs in
osteoarthritis
) or damaged,
the movement of that joint may be
painful or severely restricted.
Fibrocartilage contains a large pro-
portion of collagen and is solid and
strong. This type of cartilage makes up
the discs that are situated between the
bones of the spine (see
disc, interverte-
bral
) .
It also forms the shock-absorbing
pads of tissue w ithin joints.
Elastic cartilage is soft and rubbery.
It is found in structures such as the
outer ear and the
epiglottis
.
caruncle
A general term for a small, fleshy swel-
ling. Caruncles can be normal, such as
the red, raised tissue in the inner cor-
ner of the eye. Some are abnormal,
appearing as polyp-like growths; this
type may be found, for example, at the
opening of the urethra (the tube by
w hich urine leaves the bladder).
Casal’s necklace
A red rash forming a clearly defined
ring around the neck. It is a symptom
of
pellagra
,
a disorder caused by lack of
the B vitamin niacin in the diet.
cascara
A type of stimulant
laxative drug
,
w hich
can be used when rapid onset of action
is needed. Cascara is now rarely used.
caseous abscess
An
abscess
(collection of pus) contain-
ing
matter that
resembles
curds
or
cottage cheese. Caseous abscesses are
most commonly due to
tuberculosis
.
cast
A rigid casing applied to a lim b or other
part of the body to hold a broken bone
or dislocated joint in position as it
heals. Most casts are made of bandages
impregnated with resin or
plaster of
Paris
,
w hich are applied while wet and
harden as they dry. Casts are removed
using an electric saw that cuts through
the cast but does not damage the skin.
castor oil
A colourless or yellow-tinged oil that is
obtained from the leaves of the castor
oil plant, R
icinus communis
. If taken oral-
ly, castor oil irritates the lining of the
small intestine and has a powerful laxa-
tive action that completely empties the
bowel. Zinc and castor oil are com-
bined in a soothing ointment to treat
conditions such as
nappy rash
.
castration
The surgical removal of the testes (see
orchidectomy
) .
The term “castration” is
sometimes also used to refer to removal
of the ovaries (see
oophorectomy
).
Castration is performed when the
testes or ovaries are diseased. It may
also be carried out in order to reduce
the level of
testosterone
(a male sex hor-
mone produced in the testes)
or of
oestrogen
(a female sex hormone pro-
duced in the ovaries) in people who
have certain types of
cancer
that are
stimulated by these hormones.
Orchidectomy
and
oophorectomy
are performed less frequently since the
introduction of
gonadorelin
analogues,
w hich are drugs that also act to reduce
the amount of testosterone and oestro-
gen produced by the body.
catabolism
A
chemical process
by w hich
con-
stituents of food stored in the body
(for example, fats) are broken down,
releasing energy into the body cells
(see
biochemistry; metabolism
) .
catalepsy
A physical state in w hich the muscles
of the face, body, and limbs stay in a
sem i-rigid, statuelike position for m in-
utes, hours, or even days. Catalepsy
sometimes occurs in people who have
schizophrenia
or
epilepsy
but may also be
due to brain disease or certain drugs.
catalyst
A substance, such as an
enzyme
,
that
increases the rate of a chemical reaction
without being permanently changed
itself by that reaction.
cataplexy
A sudden loss of muscle tone, causing
an involuntary collapse without loss of
consciousness.
Triggered
by
intense
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