CARPAL TUNNEL SYNDROME
CATARACT
neck. Just above the level of the
larynx
(voice-box), each carotid artery divides to
form an external carotid artery and an in-
ternal carotid artery. The external arteries
have multiple branches that supply most
tissues in the face, scalp, mouth, and jaws;
the internal arteries enter the skull to
supply the brain and eyes. At the base of
the brain, branches of the
2
internal ca-
rotids and the basilar artery join to form
a ring of vessels called the circle of Willis.
Narrowing of these vessels may be as-
sociated with
transient ischaemic attack
(TIA
); obstruction of them causes a
stroke
.
carpal tunnel syndrome
Numbness,
tingling, and pain in the thumb, index
finger, and middle fingers caused by
compression of the
median nerve
at the
wrist. Symptoms may be worse at night.
The condition results from pressure on
the nerve where it passes into the hand
via a gap (the “carpal tunnel'') under a
ligament at the front of the wrist. It is
common among keyboard users. It also
occurs without obvious cause in middle-
aged women, and is associated with
pregnancy, initial use of
oral contracep-
tives
,
premenstrual syndrome
,
rheumatoid
arthritis, myxoedema,
and
acromegaly.
The condition often disappears without
treatment. Persistent symptoms may be
treated with a
corticosteroid drug
injected
under the ligament, or the ligament may
be cut to relieve pressure on the nerve.
carpus
The
8
bones of the
wrist.
carrier
A person who is able to pass on
an infectious or inherited disease with-
out actually suffering from it.
car sickness
See
motion sickness
.
cartilage
A type
of
connective tissue
made up of varying
amounts of the gel-
like substance
colla-
gen
. Cartilage forms
an important struc-
tural component of
various parts of the
skeletal system, in-
cluding the
joints
.
There are 3 main
types. Hyaline car-
tilage is a tough,
JOINT
smooth tissue that
C
lines the surfaces of joints. Fibrocarti-
lage is solid and strong and makes up
the intervertebral discs that are situated
between the bones of the spine and the
shock-absorbing pads in joints. Elastic
cartilage is soft and rubbery and found
in structures such as the outer ear and
the
epiglottis.
cast
A rigid casing applied to a limb 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
plaster o f Paris,
which
are applied wet and harden as they dry.
castor oil
A colourless or yellow-tinged
oil obtained from the leaves of the cas-
tor oil plant. Given orally, castor oil has
a laxative action. Zinc and castor oil are
combined in a soothing ointment for
conditions such as nappy rash.
castration
The removal of the testes
(see
orchidectomy).
The term is some-
times used for removal of the ovaries
(see
oophorectom y
). Castration is per-
formed when organs are diseased or to
reduce the level of testosterone or of
oestrogen in people who have certain
types of cancer that are stimlated by
these hormones.
catabolism
A
chemical
process
by
which constituents of food stored in the
body (for example, fats) are broken
down, releasing energy into body cells
(see
biochemistry; m etabolism
).
catalepsy
A physical state in which the
muscles of the face, body, and limbs are
maintained in a semi-rigid, statue-like
position for minutes, hours, or even days.
Catalepsy occurs in people with
schizo-
phrenia
or
epilepsy,
but may also be
caused by brain disease or some drugs.
cataplexy
A sudden loss of muscle tone,
causing an involuntary collapse without
loss of consciousness. Cataplexy is trig-
gered by intense emotion, particularly
laughter, and occurs almost exclusively
in those suffering from
narcolepsy
and
other sleep disorders.
cataract
Loss of transparency of the
crystalline
lens
of the eye, due to
changes in its delicate protein fibres. At
an advanced stage, the front part of the
lens becomes densely opaque, but the
cataract never causes total blindness.
Almost everyone over 65 has some
112
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