In anatomy, the anus (from Latin ānus "ring (circle), anus") is the external opening of the rectum. Closure is controlle by sphincter muscles. Feces are expelled from the body through the anus during the act of defecation, which is the primary function of the anus. Most animals—from simple worms to elephants and humans—have a tubular gut, with a mouth at one end and an anus at the other.