Understanding Bowel Function

The Effect of Weak Bowel Muscles – Understanding Normal Bowel Function and Why Incontinence Occurs

It is important to know how normal bowels work to fully understand bowel incontinence, also called anal leakage. When your bowels function normally, your muscles and nerves of the rectum are able to control the release of your stool (waste matter). 

Bowel leakage can occur if there are problems with the muscles and nerves in the rectum and pelvis.1 Damage or weakening of these nerves and muscles can cause accidents – especially with loose stool, due to its difficulty to control.  

How do normal bowels work?

The ability to hold stool, called continence, requires the rectum, anus and nervous system to be working normally. Two groups of muscles in the wall of the anus and rectum are responsible for holding the stool in the rectum, the outer muscle group (external anal sphincter) and the inner muscle group (internal anal sphincter).1

The process of a normal bowel movement begins when the rectum fills with stool. The brain then sends signals to the anus and anal sphincter muscles to either

  • Relax—which allows the rectum to release stool when desired, or

  • Contract—to hold stool in when a bowel movement is not wanted

The muscles in the anal canal work together to control the release of stool



Remember, the more you know about normal bowel control (or “ bowel continence”), the better you will understand your bowel incontinence. Remember, bowel incontinence is not a normal part of aging- it affects men and women of all ages, races and backgrounds.




Read more about the causes of bowel incontinence to gain a better understanding of why you may have this condition.


  1. American College of Gastroenterology. Fecal Incontinence. Available at http://gi.org. Accessed September 13, 2019.