Back to last page Diseases and Conditions What Is It? The anus
is that part of the intestinal tract that passes through the
muscular canal of the pelvis and anal sphincters. It is the
final orifice through which stool passes out of the body. In
adults, the anus is 4 to 5 centimeters long. The lower half of
the anal canal has sensitive nerve endings. There are blood
vessels under the lining, and in its mid portion there are
numerous tiny, anal glands. This article describes four
disorders that cause anal pain and irritation: - Anal fissure --
An anal fissure, also called an anorectal fissure, is a linear
split or tear in the lining ("anoderm") of the lower anal canal.
Most anal fissures happen when a large, hard stool overstretches
the anal opening and tears the delicate anoderm. Less often,
anal fissures develop because of prolonged diarrhea,
inflammatory bowel disease or sexually transmitted diseases
involving the anorectal area. Acute (short-term) anal fissures
are usually superficial and shallow, but chron