CLAVICLE
the hepatic vein and rejoins the main
systemic
circulation via the inferior
(lower) vena cava.
Venous blood returns to the right
atrium of the heart to enter the pul-
monary circulation. It is pumped from
the right ventricle through the pulm o-
nary artery to the lungs, where carbon
dioxide is exchanged for oxygen. The
reoxygenated blood then returns via
the pulmonary veins to the heart and
re-enters the systemic circulation.
On its journey from the heart to the
body tissues, blood is forced along the
arteries at high pressure. In contrast,
blood flowing through the veins and
back to the heart is at low pressure. It is
kept moving by muscles in the limbs,
w hich compress the veins and thus
squeeze blood through them, and by
valves in the veins that prevent the
blood from flowing backwards.
(See
also
lymphatic system
;
respiration
) .
circumcision
Surgical removal of the foreskin of the
penis
.
Circum cision
is
usually
per-
formed
on
newborn
babies
for
religious or hygienic reasons. In some
cases, it may be medically required to
treat
phimosis
(a tight foreskin that
causes ballooning on urination), recur-
rent attacks of
balanitis
(infection under
the
foreskin
due
to
retained secre-
tions), or
paraphimosis
(painful com-
pression of the shaft of the penis by a
retracted foreskin).
circumcision, female
Removal of all or some parts of the
female external genitalia: the
clitoris
,
labia majora, and labia minora
(see
labia
) .
Female circum cision is some-
times combined with narrowing of the
entrance to the
vagina
.
Female circum cision is common in
certain parts of Africa but has no valid
medical purpose. It can cause retention
of urine and injuries during sexual
intercourse and childbirth.
cirrhosis
A condition of the
liver
that results
from long-term damage to liver cells.
In cirrhosis, bands of fibrosis (internal
scarring)
develop, leaving
nodules
of
regenerating cells that are inadequately
supplied w ith blood. Liver function is
gradually impaired; the liver no longer
effectively
removes
toxic
substances
from the blood (see
liver failure
) .
The
distortion and fibrosis also lead to
por-
tal hypertension
(abnormally high blood
pressure in the veins leading from the
intestines and spleen to the liver).
CAUSES
The most common cause of cirrhosis is
excessive
alcohol
consumption. Another
possible cause is one of the forms of
chronic
hepatitis
(inflammation of the
liver).
Other
causes, which are rare,
include
disorders
of
the
bile ducts
;
haemochromatosis
,
in w hich
increased
iron absorption occurs;
Wilson’s disease
(an increase in copper absorption);
cystic
fibrosis
,
which causes obstruction of the
bile ducts with mucus; and
heart failure
.
SYMPTOMS AND COMPLICATIONS
Cirrhosis may go unrecognized until
symptoms such as m ild
jaundice
,
oede-
ma
(an accumulation of fluid in body
tissues) and vomiting of blood develop.
There may be enlargement of the liver
and spleen. Men may experience loss of
body
hair
and
enlargement
of the
breasts due to an imbalance in sex hor-
mones caused by liver failure.
Complications
of cirrhosis include
ascites
(an accumulation of fluid in the
abdominal cavity),
oesophageal varices
(enlarged veins w ithin the oesophagus
w all), and
hepatoma
(liver cancer). Cir-
rhosis may also cause toxins to build
up in the brain, producing symptoms
such as confusion and coma (see
hepa-
tic encephalopathy
) .
TREATMENT
Treatment is focused on slowing the
rate at w hich liver cells are being dam-
aged, if possible by treating the cause.
Any complications w ill also be treated.
In some cases, however, the cirrhosis
progresses and a
liver transplant
may
need to be considered.
cisplatin
An
anticancer drug
used to treat some
cancers of the
testis
and the
ovary
.
citalopram
An
antidepressant drug
belonging to a
group
called
selective
serotonin
re-
uptake inhibitors
(SSRIs). Citalopram
takes up to four weeks to reach its full
effect; it gradually improves the user’s
mood, energy levels, and level of inter-
est in everyday activities.
The drug may cause gastrointestinal
problems such as nausea, vomiting, or
diarrhoea, but these usually diminish
with continued use. Citalopram may
also cause drowsiness and, for this rea-
son, people taking the drug should
avoid alcohol, and should not carry out
activities such as driving vehicles until
they have learned how strongly citalo-
pram affects them.
CJD
The abbreviation for
Creutzfeldt-Jakob
disease
.
CK
The abbreviation for
creatine kinase
.
clamp
An instrument that is used during sur-
gical procedures to compress the cut
end of an organ or blood vessel tem-
porarily, in order to prevent leakage of
blood or other fluids.
clap
A slang term for
gonorrhoea
.
clarithromycin
An
antibiotic drug
that belongs to the
macrolide
group.
Clarithromycin
is
used to treat infections of the skin and
the respiratory tract.
classic migraine
A type of
migraine
attack accompanied
by an aura (neurological disturbances),
nausea, and vomiting.
claudication
A cramplike pain in a muscle, most
often in the legs, due to inadequate
blood supply. Claudication in the legs is
usually caused by blockage or narrow-
ing of arteries due to
atherosclerosis
(see
peripheral
vascular disease
) .
In
intermittent claudication, pain is felt in
the calves after walking a certain dis-
tance and is relieved by rest.
A rarer cause is spinal
stenosis
(nar-
rowing of the canal carrying the spinal
cord), causing pressure on the nerve
roots that pass into either leg.
claustrophobia
An intense fear of being in enclosed
spaces, such as lifts or tunnels, or of
being in crowded areas. The usual treat-
ment
is
behaviour therapy
involving
techniques
that gradually lessen the
patient’s anxiety. (See also
phobia
.)
clavicle
The collarbone. The two clavicles, one
on each side, form joints with the top
of the sternum (breastbone) and the
scapula (shoulderblade). The clavicles
support the arms and transmit forces
from the arms to the central skeleton.
C
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