View source for Rectum - Anatomy & Physiology

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==Introduction==


==Structure==

*Exists dorsal to the [[Reproductive System|reproductive organs]], [[Urinary System - Anatomy & Physiology|bladder]] and urethra.
*The cranial portion of the rectum is attached to the dorsal body wall by a short mesorectum which is a continuation of the mesocolon.
*The mesorectum is reflected to continue with the parietal peritoneum of the pelvic cavity and to cover the urogenital organs ventrally.
**This forms the '''rectogenital pouch'''.
**Therefore the most distal part of the rectum is retroperitoneal.
***This distal, retroperitoneal part is directly attached to the vagina in the female and to the urethra in the male.
***The retroperitoneal space is filled with soft tissue rich in fat.
*The '''anal canal''' joins the bowel to the exterior.
**This is a short passage derived from the proctodeum (formed by invagination of the surface ectoderm).
**Before joining the anal canal, the rectum becomes dilated to form the ''rectal ampulla''.
*At the rectoanal junction, the lumen is constricted by longitudinal folds in the mucosa.
**These are normally pressed together to occlude the lumen.
*There are ''two'' anal sphincters:
**'''Internal anal sphincter''', formed by thickening of the circular smooth muscle of the gut and under autonomic control.
**'''External anal sphincter''', formed from striated skeletal muscle and under voluntary control.

==Function==


==Vasculature==


==Innervation==


==Lymphatics==


==Histology==
*Epithelium is columnar.

==Species Differences==


==Links==