The anus
This page tells you about the anus. There is information about
The anus
The anus is part of the large bowel that opens to the outside of the body. It is the tube that your stools pass through as you empty your bowels.
The cells of the anus
The lining of the anus is made of flat skin-like cells called squamous cells. Most anal cancers are squamous cell cancers.
The anus is the part of the large bowel that opens to the outside of the body. It is the tube that your stools pass through as you empty your bowels. You may hear it called the ‘anal canal’. It is about 3 cm long, and is at the end of your rectum. There is more information about the large bowel in our bowel cancer section.
The lining of the canal between the outer skin (the perianal area) and the rectum is made up of squamous cells. Most anal cancers are squamous cell cancers.
The area where the anal canal meets the rectum is called the transitional zone. Here the lining of the anus changes and is made up of both squamous and glandular cells. Glandular cells make the mucus that helps stools (faeces) pass through the anus smoothly. Doctors call this area 'the dentate line'. A rare type of anal cancer can develop from these cells, called adenocarcinoma of the anus.
The lower part of the anus is called the anal margin. The anal margin contains muscles called the anal sphincters. The external anal sphincter is the muscle you use to control your bowel movements.
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