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In humans, the anus (pl.: anuses or ani; from Latin ānus, "ring", "circle") [1] [2] is the external opening of the rectum located inside the intergluteal cleft.Two sphincters control the exit of feces from the body during an act of defecation, which is the primary function of the anus.
The canal is differentiated from the rectum by a transition along the internal surface from endodermal to skin-like ectodermal tissue. The anal canal is traditionally divided into two segments, upper and lower, separated by the pectinate line (also known as the dentate line): upper zone (zona columnaris) mucosa is lined by simple columnar ...
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.
It is an important anatomical landmark in humans, and forms the boundary between the anal canal and the rectum according to the anatomic definition. [1] Colorectal surgeons instead define the anal canal as the zone from the anal verge to the anorectal ring (palpable structure formed by the external anal sphincter and the puborectalis muscle). [1]
It is about 5 mm thick, and is formed by an aggregation of the smooth (involuntary) circular muscle fibers of the rectum. [citation needed] The internal anal sphincter aids the sphincter ani externus to occlude the anal aperture and aids in the expulsion of the feces. Its action is entirely involuntary. It is normally in a state of continuous ...
The largest part of the GI tract is the colon or large intestine. Water is absorbed here and the remaining waste matter is stored prior to defecation. [2] There are many specialised cells of the GI tract. These include the various cells of the gastric glands, taste cells, pancreatic duct cells, enterocytes and microfold cells.
Stratified columnar epithelium is a rare type of epithelial tissue composed of column-shaped cells arranged in multiple layers. It is found in the conjunctiva, pharynx, anus, and male urethra. It also occurs in embryo.
The length of the human colon is, on average 160.5 cm (measured from the bottom of the cecum to the colorectal junction) with a range of 80 cm to 313 cm. [11] The average inner circumference of the colon is 6.2 cm. [10] Thus, the inner surface epithelial area of the human colon has an area, on average, of about 995 cm 2, which includes ...