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| The '''anus''', in ], is the external opening of the ]. It is controlled by ] ]s. ] are expelled from the body through the anus during the act of ], which is the primary function of the anus. | The '''anus''', in ], is the external opening of the ]. It is controlled by ] ]s. ] are expelled from the body through the anus during the act of ], which is the primary function of the anus. | ||
| == The human anus and its sphincters in |
== The human anus and its sphincters in defecation == | ||
| The human anus has two ]s, one internal, the other external. These hold the anus closed until the body is ready to defecate. | The human anus has two ]s, one internal, the other external. These hold the anus closed until the body is ready to defecate. | ||
Revision as of 16:52, 4 December 2003
The anus, in anatomy, is the external opening of the rectum. It is controlled by sphincter muscles. Faeces are expelled from the body through the anus during the act of defecation, which is the primary function of the anus.
The human anus and its sphincters in defecation
The human anus has two anal sphincters, one internal, the other external. These hold the anus closed until the body is ready to defecate.
When the rectum is full the increase in intrarectal pressure forces the walls of the anal canal apart allowing the fecal matter to enter the canal. The rectum shortens as material is forced into the anal canal and peristaltic waves propel the feces out of the rectum. The internal and external sphincters of the anus allow the feces to be passed by muscles pulling the anus up over the exiting feces.
See also anal sex, enema, cloaca.
For the words "asshole" and "arsehole", and the card game of that name, see Asshole (word)