Figure 1636

Drawing of the rectum and anal canal. The rectum and anal canal are the terminal portions of the large intestine. They are lined by the colorectal mucosa that possesses a simple columnar epithelium containing mostly goblet cells and numerous anal glands. In the anal canal the simple columnar epithelium undergoes transition into a stratified columnar (or cuboidal) epithelium and then to a stratified squamous epithelium. This transition occurs in the area referred as the anal transitional zone, which occupies the middle third of the anal canal between the colorectal zone and the squamous zone of the perianal skin.

transverse rectal folds colorectal zone transitional zone squamous zone anal sinuses

ampulla ot rectum lymphatic nodules mucosal folds anal columns internal anal sphincter external anal sphincter ampulla ot rectum transverse rectal folds colorectal zone transitional zone squamous zone lymphatic nodules anal sinuses mucosal folds anal columns internal anal sphincter external anal sphincter

internal anal sphincter anal valve external ^ anáj^p sphincter

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