The anus is the opening where the gastrointestinal tract ends and exits the body. The anus starts at the bottom of the rectum, the last portion of the colon (large intestine). The anorectal line separates the anus from the rectum.
Tough tissue called fascia surrounds the anus and attaches it to nearby structures.
Circular muscles called the external sphincter ani form the wall of the anus and hold it closed. Glands release fluid into the anus to keep its surface moist.
A plate-like band of muscles, called the levator ani muscles, surround the anus and form the floor of the pelvis. A network of veins lines the skin of the anus.