The levator ani muscles, a band of muscles that appears like  plate, comprise  the pelvic floor and surround  the anus. Meanwhile, the anal wall is consists of circular muscles known as the external sphincter ani, which keep the anus close.

Externally, the anus is a body opening just adjacent to the perineum, posterior to the scrotum in males or behind the vaginal opening in females . As an orifice or opening, the anus function as portal of exit for the digestive waste or feces (stool) during defecation. It is a significant structure checked by medical professionals upon a child’s birth due to the incidence of imperforate anus, a congenital condition by which a newborn’s anus is blocked or there is no opening through which the feces can pass by during defecation.