The
human anus (from
Latin meaning "ring", "circle") is the external opening of the
rectum. 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 in females and behind the scrotum in males.