muscle fatigue, unrefreshing sleep, and
headaches. The syndromeis often asso-
ciated with depression or anxiety.
There is no specific diagnostic test for
chronic fatigue syndrome, and investi-
gations are usually aimed at excluding
other possible causes of the symptoms,
such as anaemia. A physical examination,
blood tests, and psychological assess-
ment may be carried out. If no cause can
be found, diagnosis of chronic fatigue
syndrome is made from the symptoms.
Analgesic drugsor antidepressant drugs
may relieve the symptoms. Physiotherapy
or psychotherapymay also be helpful.
Chronic fatigue syndrome is a long-
term disorder, but the symptoms clear
up after several years in some people.
chronic obstructive pulmonary dis-
easeSee pulmonary disease, chronic
obstructive.
ciclosporinAn immunosuppressant drug
used following transplant surgery. The
drug reduces the risk of tissue rejection
and the need for large doses of cortico-
steroid drugs. Ciclosporin may need to
be taken indefinitely after a transplant. It
is also used to treat rheumatoid arthritis
and other autoimmune disorders. Because
ciclosporin suppresses the immune sys-
tem, it increases the susceptibility to
infection. Swelling of the gums and in-
creased hair growth are fairly common.
Ciclosporin may also cause kidney dam-
age, and regular monitoring of kidney
function is required.
ciliaHair-like filaments on the surface
of some epithelial cells (see epithelium).
Cilia are found particularly in the linings
of the respiratory tract, where they pro-
pel dust and mucus out of the airways.
ciliary bodyA structure in the eyecon-
taining muscles that alter the shape of
the lensto adjust focus. (See also
accommodation.)
cimetidineAn H 2 - receptor antagonist
used as an ulcer-healing drug. Cimeti-
dine promotes the healing of gastric
and duodenal ulcers (see peptic ulcer)
and reduces the symptoms of oeso-
phagitis. Side effects include dizziness,
fatigue, and rashes. More rarely, the drug
causes impotence and gynaecomastia.
CINThe abbreviation for cervical intra-
epithelial neoplasia.cinnarizineAn antihistamine drugused
to control nausea and vomiting due to
travel sickness or to reduce nausea and
vertigo in inner-ear disorders, such as
labyrinthitisand Ménière’s disease. High
doses are sometimes used to improve
circulation in peripheral vascular disease
and Raynaud’s disease. Side effects may
include drowsiness, lethargy, dry mouth,
and blurred vision.
ciprofloxacinAn antibacterial drugused
mainly to treat infections of the respira-
tory, gastrointestinal, and urinary tracts.
circadian rhythmsAny biological pat-
tern based on a cycle approximately 24
hours long, also called a diurnal rhythm.
(See also biorhythms.)
circulation, disorders ofConditions af-
fecting blood flow around the body (see
arteries, disorders of; veins, disorders of).
circulatory system The heartand blood
vessels, which together maintain a con-
tinuous flow of blood throughout the
body. The system provides tissues with
oxygen and nutrients, and carries away
waste products. The circulatory system
consists of 2 main parts: the systemic
circulation, which supplies blood to the
whole body apart from the lungs; and the
pulmonary circulation to the lungs.
Within the systemic circulation, there is
a bypass (the portal circulation), which
carries nutrient-rich blood from thestom-
ach, intestine, and other digestive
organs to the liver for processing, stor-
age, or re-entry into general circulation.
In the systemic circulation, oxygen-rich
blood from the pulmonary circulation is
pumped under high pressure from the
left ventricleof the heart into the aorta,
from where it travels through arteries
and smaller arterioles to all parts of the
body. Within body tissues, the arterioles
branchinto networks of fine blood ves-
sels called capillaries. Oxygen and other
nutrients pass from the blood through
the capillaries’ thin walls into body tis-
sues; carbon dioxide and other wastes
pass in the opposite direction. Deoxy-
genated bloodis returned to the heart
via venules, veins, and the venae cavae.
Venous blood returns to the right atri-
um of the heart to enter the pulmonary
circulation. It is pumped from the right
ventricle through the pulmonary arteryCHRONIC OBSTRUCTIVE PULMONARY CIRCULATORY SYSTEMC