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Cancer

Anatomy of the Anus

The anus is the last part of the digestive tract. It’s at the end of the rectum. It's where stool comes out of the body. It consists of a muscular ring (called a sphincter) that opens during a bowel movement to allow stool (feces) to pass through, as well as flat cells that line the inside of the anus. Most anal cancers start in these flat lining cells. These are also called squamous cells. The lower part of the anus, where it meets the skin, is called the anal margin.

Cross section of anus.

Online Medical Reviewer: Jessica Gotwals RN BSN MPH
Online Medical Reviewer: Raymond Turley Jr PA-C
Online Medical Reviewer: Todd Gersten MD
Date Last Reviewed: 4/1/2023
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