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Anus - Anatomy & Physiology (view source)
Revision as of 18:07, 10 December 2010
, 18:07, 10 December 2010no edit summary
===Porcine===
===Porcine===
Also have '''anal sacs'''.
Also have '''anal sacs'''.
==Histology==
[[Image:Anal Glands.jpg|thumb|right|150px|Anal Glands- © RVC 2008]]
*At the anus, the columnar intestinal epithelium is replaced by the stratified squamous keratinised epithelium of the skin.
*The '''anal canal''' joins the bowel to the exterior and is the last 2-3cm of the alimentary tract.
**This is a short passage derived from the proctodeum (formed by invagination of the surface ectoderm).
*Sebaceous and large apocrine sweat glands both occur in this region in association with the anal sphincters.
**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.
*As the muscosa changes from columnar to cutaneous, three zones are created:
**'''Columnar'''
***Has many longitudinal folds.
***Divided from the rectum by the ''anorectal line''.
****This is a line where the mucosa is stratified squamous epithelium containing lots of lymphoid tissue.
**'''Intermediate'''
***Divided from the cutaneous zone by the ''anocutaneous line''.
**'''Cutaneous'''
***Skin.
***Stratified squamous keratinised epithelium.
***Surrounds the anus.
***Excretory ducts of the '''anal sacs''' open into this region.
==Links==
==Links==
'''Click here for information on the[[Intestines, Small and Large - Pathology|pathology Of The Small and Large Intestines]].'''
'''Click here for information on the[[Intestines, Small and Large - Pathology|pathology Of The Small and Large Intestines]].'''
[[Category:Large Intestine - Anatomy & Physiology]]
[[Category:Large Intestine - Anatomy & Physiology]]
[[Category:To Do - AimeeHicks]][[Category:To Do - AP Review]]
[[Category:To Do - AimeeHicks]][[Category:To Do - AP Review]]