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The anus is an opening at the opposite end of an animal's digestive tract from the mouth. It is used for expelling unwanted solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest, such as bones; food material after all the nutrients have been extracted, for example cellulose or lignin; ingested matter which would be toxic if it remained in the digestive tract; and dead or excess gut bacteria and other endosymbionts. |
Anus vs Women, 
