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"What do I need to know about the anatomy
of the colon and rectum?"
The colon is the end of the intestinal
tract. It is 8 to 12 feet in length. It begins at the junction of
the small bowel called the ileocecal valve, goes up along the right
side of the abdomen, across the top and down the left side of the
abdomen. These are respectively termed the ascending, transverse
and descending sections of the colon . The lower part of the colon
is called the sigmoid, and the sigmoid joins the rectum about 15
centimeters (6 inches) from the anus. There is no difference between
the colon and rectum and these are just terms to designate an area
of the large intestine. The rectum is 15 centimeters in length and
is that area just above the anus.
The anus is a muscle which closes
the colon. It is this outlet obstruction which allows us to be continent.
We define continence as the ability to defer defecation until a
socially convenient time. This says nothing about the number of
bowel movements, the quality of the bowel movements (liquid or solid),
but this definition does point out that the bowel habits should
not have a significant influence on the quality of life of the individual.
Our ability to control our bowels until a socially convenient time
is controlled by the sphincter muscles which act as a plug and the
rectum, which acts as a storage area. If the rectum is inflamed
or scarred, then it does not work properly as a storage vessel.
If either the anal muscle or the rectum is not working properly,
control of the bowels is difficult. After surgical removal of the
rectum, bowels movements will, at least temporarily, be more frequent
and urgent. This is because the storage area is not working properly.
It will recover and adjust after several weeks.
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