Medical Q&As

Anal sphincter - what is it?

Could you please give me some information on the sphincter muscle?

For the purpose of answering this question I assume that the sphincter you are enquiring about is the anal sphincter. There are several sphincters in the body and the term refers to a ring of muscle that controls an opening or exit point from one area to another. The anus is the terminal portion of the intestine and it connects the rectum to the exterior of the body. The anal sphincter is a tight ring of muscle at the opening of the anus that remains closed until a stool is passed out from the rectum. The stool in the rectum causes pressure on the wall of the rectum, which in turn causes the anal sphincter to relax. Relaxation of the sphincter allows the stool to be evacuated from the body. If normal tone is not maintained in the sphincter, for whatever reason, faecal incontinence ensues. Sometimes the anal sphincter is stretched as part of the treatment for haemorrhoids or piles. The rationale for that procedure is that increased muscle tone in the sphincter can be a factor in the development of piles.