Difference between revisions of "Rectum - Anatomy & Physiology"
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| Line 18: | Line 18: | ||
**These are normally pressed together to occlude the lumen. | **These are normally pressed together to occlude the lumen. | ||
*There are ''two'' anal sphincters: | *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== | ==Function== | ||
Revision as of 08:21, 12 July 2008
Introduction
Structure
- Exists dorsal to the reproductive organs, 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 anal canal joins the bowel to the exterior.
- This is a short passage derived from the proctodeum (formed by invagination of the surface ectoderm).
- 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.