The anus, or 'mahogany knot' is a part of the body controlled by a sphincter muscle. It has three primary functions.
The same rules apply for animals. Including #2 in some parts of the world.
1) To expel waste matter (feces, dogs eggs) from the body.
2) To provide an alternative orifice on a lady/animal for penis insertion. Or as the main orifice for men.
3) To be used as an insult
"John, you is anus."
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