a-short-review-of-histology

Anal Canal:

The anal canal is the terminal part of the alimentary canal
Its general morphology conforms with the basic gut plan
The rectum is the storage site for the stools until defaecation occurs
The anal canal, which is only 1-2 cm in length functions mainly as a sphincter to assist in the maintenance of continence
The epithelium of the mucous membrane is stratified squamous nonkeratinising epithelium
This in part reflects a transitional change between the simple columnar epithelium of the main part of the gut tube, and the stratified squamous keratinising epithelium of the skin
However, it also reflects the wear and tear that the epithelium of the anal canal will suffer during the passage of the stools during defaecation
The inner (circular) layer of the muscularis externa of the anal canal is thickened and forms the internal anal sphincter
In addition, there is a band of skeletal muscle around the outside of the anal canal which forms the external anal sphincter
The external anal sphincter is not part of the gut tube