Changes

***Surrounds the anus.

***Surrounds the anus.

***Excretory ducts of the '''anal sacs''' open into this region.

***Excretory ducts of the '''anal sacs''' open into this region.

*Sebaceous and apocrine sweat glands are associated with the anal sphincters.

*Sebaceous and apocrine sweat glands both occur in this region an with the anal sphincters.

==Species Differences==

==Species Differences==