1,362
edits
Changes
Jump to navigation
Jump to search
→Histology
==Histology==
==Histology==
*At the anus, the columnar intestinal epithelium is replaced by the stratified squamous epithelium of the skin.
*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 epithelium.
***Surrounds the anus.
***Excretory ducts of the anal sacs open into this region.
****Anal sacs are large, coiled apocrine tubules.
****Anal sacs have many glands in their walls.
****These glands are tubuloalveolar and produce a fatty secretion.
****Anal sacs are clinically important as they are commonly diseased in dogs - frequently, they become enlarged due to accumulated secretion.
==Species Differences==
==Species Differences==