It is surrounded by nerves that detect expansion of the rectum and signals a sensation of urgency to let us know when it is time to have a bowel movement. Below the the rectum is the area known as the pelvic floor, which is made up of many different muscles. The puborectalis muscle and the external anal sphincter are voluntarily contracted to prevent leakage of stool when you feel fullness in the rectum. The internal anal sphincter is an involuntary muscle that helps to prevent leakage from the rectum. When it's time to have a bowel movement, all these muscles relax so the stool can pass through the anus.
Fecal incontinence is a symptom.
It occurs when something is wrong within the complex mechanisms of the body that maintain continence. Incontinence can result from a variety of factors, such as functional impairment or structural damage to certain muscles or nerves. Muscles and nerves interact to propel waste contents, sense its presence, and permit voluntary storage and elimination. The pelvic floor plays an important role in maintaining continence. This is a group of muscles that span the underlying surface of the bony pelvis.