COLON,CANCER OF
fracture is usually the result of putting
out a hand to lessen the impact of a
fall. It is more common in elderly peo-
ple, due to weakening of the bones by
aging or
osteoporosis
.
The broken bones are manipulated
back into place and set in a
cast
.
Heal-
ing of the bones takes up to six weeks.
Hand and w rist movements usually
return to norm al, but there may be
m inor w rist deformity.
Collet-Sicard syndrome
A condition resulting from damage to
the
cranial nerves
that control muscles in
the tongue and throat. It is usually due
to a
head injury
or to compression of the
nerves by a tumour. The syndrome
causes
paralysis
of muscles
in
the
tongue, palate, throat, larynx (voice-
box), and neck on one side. There is no
cure, but the cause is treated if possible.
collodion
A syrupy mixture of
ether
,
alcohol
,
and
pyroxylin used in skin preparations for
m inor cuts and abrasions. Collodion
acts by evaporating rapidly to leave a
protective film over the area.
colloid
A form of fluid that is sim ilar to a sus-
pension (a fluid consisting of insoluble
particles of a substance suspended 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 separated out of the liquid by
U ln a
R a d iu s
L o w e r e n d o f
b r o k e n r a d i u s
d i s p l a c e d
b a c k w a r d s
X-ray of Colles’ fracture
This X-ray clearly shows that the lower end ofthe
broken radius has been pushed back. This gives
a classic “dinner fork” appearance when the wrist
is viewed from the side.
spinning at a very high speed. In medi-
cine,
plasma proteins
are separated from
blood and sometimes used in colloid
preparations to treat
shock
.
The term “ colloid” also refers to a
material that contains protein and is
found in the
thyroid gland
.
coloboma
A rare
birth defect
in w hich a gap exists
in the tissues of the eye. The gap may
be in the eyelid or in part of the eye-
ball, such as the
iris
,
retina
,
or
choroid
.
A
coloboma in the iris w ill be visible as a
black notch, or as a gap stretching from
the pupil to the edge of the iris.
The condition results from incom -
plete development of the eyes w hile the
baby is still an
embryo
;
this problem
may, in turn, be linked to certain
chro-
mosomal abnormalities
.
Coloboma may
range from m inor to severe. In some
cases, it may cause
blurred vision
or
decreased
visual acuity
.
colon
The major part of the large
intestine
.
STRUCTURE
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 four sections: the ascending,
transverse, and descending colons, and
the S-shaped
sigmoid colon,
w hich
connects with the rectum.
The colon consists of four layers. It
has a tough outer membrane that pro-
tects it from damage. The next layer
comprises muscles that contract and
relax rhythmically to move the intesti-
nal
contents
along
(see
peristalsis
).
Inside the muscular layer is a sub-
mucous coat containing blood vessels
and lymph vessels (see
lymphatic sys-
tem
). The
innermost layer
produces
mucus, w hich helps to lubricate the
passage of waste material.
FUNCTIONS
The main functions of the colon are to
absorb water and mineral salts from
food residue and to concentrate the
remaining waste products. The material
that remains after digestion enters the
colon from the small intestine. As this
substance passes through the colon, the
water and salts that it contains are
absorbed into the blood vessels in the
submucous coat. The waste material
becomes increasingly concentrated and
is finally expelled from the rectum in
the form of
faeces
.
(See also
digestive
system
;
intestine, disorders of.
)
colon, cancer of
A
malignant
tumour of the
colon
(the
major part of the large intestine). Can-
cers of the colon or of the rectum (the
lower part of the colon), w hich are
generally referred to as colorectal can-
cer,
are
among
the
most
common
forms of cancer. They most often occur
in people over the age of
6 0
.
CAUSES
A genetic basis has been found for
some types of colon cancer. Up to one
in three cases are associated with a
family history of colon disease. In par-
ticular,
an
inherited
disorder
called
familial
adenomatous
polyposis
(in
w hich large numbers of polyps develop
in the colon) greatly increases the risk.
In the majority of cases, however, the
precise cause is not known. Contribu-
tory factors include diet: eating a lot of
meat and fatty foods and not enough
fibre may increase the risk. The disease
also sometimes occurs in association
w ith
ulcerative colitis.
SYMPTOMS
The first symptoms of colon cancer
include
an
inexplicable
change
in
C
185
previous page 184 BMA A Z Family Medical Encyclopedia   2004 read online next page 186 BMA A Z Family Medical Encyclopedia   2004 read online Home Toggle text on/off