The human anus from Latin anus 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 or scrotum.
NCBI Bookshelf. We all have hemorrhoids. Together with a circular muscle called the anal sphincter, they help to control bowel movements. Some might be afraid of having a physical examination or finding out that they have a serious illness.
Jump to content. Rectal prolapse occurs when part or all of the wall of the rectum slides out of place, sometimes sticking out of the anus. See a picture of rectal prolapse. There are three types of rectal prolapse. In severe cases of rectal prolapse, a section of the large intestine drops from its normal position as the tissues that hold it in place stretch.
Anal cancer is a type of cancer that forms in tissues of the anus. The anus is the opening of the rectum to the outside of the body and at the end of the GI tract. Sometimes anal cancer causes no symptoms at all.