human anus human anus in humans, the anus (from latin anus meaning "ring", "circle") is the external opening of the rectum, located inside the intergluteal cleft and separated from the genitals by the perineum. two sphincters control the exit of feces from the body during an act of defecation, which is the primary function of the anus. these are the internal anal sphincter and the external anal sphincter, which are circular muscles that normally maintain constriction of the orifice and which relaxes as required by normal physiological functioning. the inner sphincter is involuntary and the outer is voluntary. it is located behind the perineum which is located behind the vagina or scrotum. anusscheme of digestive tract, with anus marked.the anus of a female with a prominent perineal raphe (left) and a male with anal pubic hair (right).identifiersta98a05.7.05.013ta23022fma15711anatomical terminology major parts of thegastrointestinal tract upper gastrointestinal tract mouth esophagus stomach duodenum lower gastrointestinal tract small intestine jejunum ileum large intestine sigmoid colon rectum anus