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The human rectum is a part of the lower gastrointestinal tract. The rectum is a continuation of the sigmoid colon, and connects to the anus. The rectum follows the shape of the sacrum and ends in an expanded section called an ampulla where feces is stored before its release via the anal canal.
The anus is the site of potential infections and other conditions, including cancer (see anal cancer). [4] With anal sex, the anus can play a role in sexuality. Attitudes toward anal sex vary, and it is illegal in some countries. [5] The anus is often considered a taboo part of the body, [5] and is known by many, usually vulgar, slang terms.
In humans, the anal canal is approximately 2.5 to 4 cm (0.98 to 1.57 in) long, from the anorectal junction to the anus. [2] [3] [4] It is directed downwards and backwards.. It is surrounded by inner involuntary and outer voluntary sphincters which keep the lumen closed in the form of an anteroposterior sl
The internal anal sphincter, IAS, or sphincter ani internus is a ring of smooth muscle that surrounds about 2.5–4.0 cm of the anal canal.It is about 5 mm thick, and is formed by an aggregation of the smooth (involuntary) circular muscle fibers of the rectum.
The rectum of mammals (other than monotremes) is derived from the cloaca of other vertebrates, and is, therefore, not truly homologous with the "rectum" found in these species. [59] In some fish, there is no true large intestine, but simply a short rectum connecting the end of the digestive part of the gut to the cloaca.
The rectum is located at the back of the ... behind is a deep notch on either side between the ilium and the base of the sacrum that is filled by the thoracolumbar ...
The sigmoid colon is completely surrounded by peritoneum (and thus is not retroperitoneal), which forms a mesentery (sigmoid mesocolon), which diminishes in length from the center toward the ends of the loop, where it disappears, so that the loop is fixed at its junctions with the iliac colon and rectum, but enjoys a considerable range of movement in its central portion.
The external anal sphincter (or sphincter ani externus) is an oval tube of skeletal muscle fibers. [1] Distally, it is adherent to the skin surrounding the margin of the anus . [ 2 ] It exhibits a resting state of tonical contraction [ 1 ] and also contracts during the bulbospongiosus reflex .