anal sphincter

The anal sphincter is a group of muscles surrounding the bottom end of the digestive tract, specifically the anus. These muscles control the release of stool (feces) by opening and closing the opening. There are two main parts: the internal sphincter, which is involuntary and automatically manages opening and closing, and the external sphincter, which is voluntary and allows you to consciously hold or release stool. Together, they help maintain continence, meaning they keep stool inside until you're ready to have a bowel movement.