The anus is located at the end of the anus, which is a human organ located between the buttocks. In the female physiological anatomy from front to back is the urethral opening, vaginal opening, anus, generally attached above the anal canal, located between the buttocks, the role of the anus is mainly the following: first, release the waste gas produced in the human body and excrete the digestive tract. Second, excretion of waste and excretion in the human body, the discharge of these liquid things. Third, around the anus is the anal sphincter, which plays the role of gating control to prevent the involuntary overflow of intestinal contents, but also to prevent external gases, liquids, etc. into the intestinal cavity. Normally in a contracted state, the anal canal will relax under external force or some disease.