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Rectum, Anus, and Anal Sphincter

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The rectum is a muscular tube about 5 in. (12.7 cm) long that is at the end of the large intestine (colon). The rectum connects the colon to the anus, which is the opening where stool exits the body.

The internal and external anal sphincters are rings of muscle at the opening of the anus. The sphincters keep the anus closed as stool collects in the rectum. Eventually the pressure on the rectum wall causes the internal anal sphincter to relax. Conscious control over the external anal sphincter allows stool to pass out of the body through the anus.

Current as of: October 19, 2023

Author: Ignite Healthwise, LLC Staff

Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

Current as of: October 19, 2023

Author: Ignite Healthwise, LLC Staff

Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.