collagenA tough, fibrous protein. Col-
lagen is the body’s major structural
protein, forming an important part of
tendons, bones, and connective tissue.
collagen diseasesSee connective tissue
diseases.
collarboneThe common name for the
clavicle.
collar, orthopaedicA soft foam or
stiffened device that is worn to treat
pain or instability of the neck.
Colles’ fractureA break in the radius
(one of the lower-arm bones) just above
the wrist, in which the wrist and hand are
displaced backwards, restricting move-
ment and causing swelling and severe
pain. The fracture is usually the result of
putting out a hand to lessen the impact
of a fall. The broken bones aremanipulat-
ed back into position, and set in a cast.
Healing takes up to 6 weeks. Hand and
wrist movements usually return to normal,
but there may be minor wrist deformity.
colloidA state of matter similar to a
suspension (insoluble particles of a sub-
stancesuspended in a liquid). Particles
in a suspension are large and heavy
enough to be separated from the liquid
in a centrifuge. A colloid has smaller,
lighter particles that can only be sep-
arated out of a liquid by spinning at a very
high speed. In medicine, plasma pro-
teinsare separated from blood and used
in colloid preparations to treat shock.
Colloid also refers to the protein-
containing material in the thyroid gland.
colonThe major part of the large intes-
tine. The colon is a segmented tube,
about 1.3 m long and 6.5 cm wide, that
forms a large loop in the abdomen. It
consists of 4 sections: the ascending,
transverse, and descending colons, and
the S-shaped sigmoid colon, which con-
nects with the rectum. The main functions
of the colon are to absorb water and
mineral salts from the digested material
passed on from the small intestine and
to concentrate the waste material for
expulsion as faeces. The colon consists
of 4 layers: a tough outer membrane; a
layer of muscles that contract and relax
to move the contents along (see peri-
stalsis); a submucous coat containing
blood vessels that absorb water and
salts; and finally an innermost layer
that produces mucus to lubricate the
passage of material. (See also digestive
system; intestine, disorders of.)
colon, cancer ofA malignanttumour
of the colon. First symptoms of the dis-
ease include an inexplicable change in
bowel movements (either constipation
or diarrhoea), blood mixed in with the
faeces, and pain in the lower abdomen.
Sometimes, there are no symptoms until
the tumour has grown big enough to
cause an obstruction in the intestine
(see intestine, obstructionof) or perfo-
rate it (see perforation).
A genetic basis has been found for
some types of colon cancer. However, in
most cases, the precise cause is un-
known. Contributory factors include diet:
eating a lot of meat and fatty foods and
not enough fibre may increase the risk.
The disease often occurs in association
with other diseases of the colon, such
as ulcerative colitisand familial polyposis.
The chances of cure depend critically on
early diagnosis. Screening for this cancer
includes an occult blood test;if the test is
positive, sigmoidoscopyand colonoscopy
may be carried out. In most cases of colon
cancer, a partial colectomyis performed.
colon, disorders ofSee intestine, dis-
orders of.
colon, irritableSeeirritable bowel syn-
drome.
colonoscopyExamination of the inside
of the colonby means of a flexible,
fibre-optic viewing instrument called a
colonoscope, which is introduced through
the anusand guided along the colon.
Colonoscopy is used to investigate symp-
tomssuch as bleeding from the anus
and to look for disorders such as colitis,
polyps, and cancer. Instruments may be
passed through the colonoscope to take
biopsy specimens or to remove polyps.
colon, spasticSee irritable bowel syn-
drome.
colostomyAn operation in which part
of the colonis brought through an inci-
sion in the abdominal wall and formed
into a stoma,an artificial opening through
which faeces are discharged into a bag
attached to the skin. A temporary colos-
tomy may be performed at the same
time as a colectomyto allow the colon
to heal without faeces passing throughCOLLAGEN COLOSTOMY
C