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*The '''anal canal''' joins the bowel to the exterior and is the last 2-3cm of the alimentary tract.
 
*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).
 
**This is a short passage derived from the proctodeum (formed by invagination of the surface ectoderm).
*Sebaceous and apocrine sweat glands both occur in this region in association with the anal sphincters.
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*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''.
 
**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.
 
*At the '''rectoanal''' junction, the lumen is constricted by longitudinal folds in the mucosa.
 
**These are normally pressed together to occlude the lumen.
 
**These are normally pressed together to occlude the lumen.
   
*As the muscosa changes from columnar to cutaneous, three zones are created:
 
*As the muscosa changes from columnar to cutaneous, three zones are created:
 
**'''Columnar'''
 
**'''Columnar'''
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