The anal sphincter maintains normal human anal function and controls the contraction of the anus so that it can be retracted and released with ease, which is what it does. The anal sphincter is a group of muscles that surrounds the anus in several groups: the outer layer, the subcutaneous layer, and the superficial layer, which contract and control the retraction and release of the anus. When the bowels come, such as working outside, even if the bowel movement is sufficient, but the brain commanded the muscles not to relax, it will not defecate, to the toilet, the brain commanded the muscles to relax, you can defecate, in fact, this is the sphincter muscle to play a role.