Anus

The anus (from Latin anus meaning "ring", "circle") is an opening at the opposite end of human's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, food material after all the nutrients have been extracted, ingested matter which would be toxic if it remained in the digestive tract, and dead or excess gut bacteria and other endosymbionts.