Anus
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{{otheruses1|the bodily orifice}}
[[Image:Anus of a model by David Shankbone.jpg|thumb|160px|Human male anus]]
[[Image:Anus 2.jpg|thumb|160px|A human female anus from which the hair has been removed]]
In [[anatomy]], the '''anus''' (from [[Latin]] ''ānus'' "ring (circle)<ref Name="Albuquerque">{{cite book | last = Martim de Albuquerque | first = | title = Notes and Queries | publisher = Oxford University Press | date= 1873 | location = Original from the University of Michigan | pages = Page 119 | url = http://books.google.com/books?id=FEn-C_BzRdMC&pg=PA119&dq=latin+anus+ring&as_brr=1&ie=ISO-8859-1 | doi = | id = }}</ref><ref Name="O'Reilly">{{cite book | coauthors = Edward O'Reilly, John O'Donovan | title = An Irish-English Dictionary | publisher = J. Duffy | date= 1864 | location = Original from Oxford University | pages = Page 7 | url = http://books.google.com/books?id=dX8NAAAAQAAJ&pg=PA7&dq=latin+anus+ring&as_brr=1&ie=ISO-8859-1 | doi = | id = }}</ref>, anus") is the external opening of the [[rectum]]. Closure is controlled by [[sphincter]] [[muscle]]s. [[Feces]] are expelled from the body through the anus during the act of [[defecation]], which is the primary function of the anus. Most animals—from simple worms to elephants and humans—have a tubular [[gut]], with a [[mouth]] at one end and an anus at the other.
The anus plays a role in sexuality, though attitudes towards [[anal sex]] vary and it is even illegal in some countries.{{Fact|date=April 2008}} The anus is also the site of potential infections and other conditions including [[cancer]]. The subject is often considered a [[taboo]] part of the body, and it is known by a large number of usually [[vulgar]] [[slang]] terms. The traditional polite synonym for anus was [[Wiktionary:fundament|fundament]], though this [[euphemism]] is rarely heard now that medical terms are widely acceptable.
== Role in defecation ==
{{main|Defecation}}
Intra-rectal pressure builds as the [[rectum]] fills with feces, pushing the feces against the walls of the [[anal canal]]. Contractions of abdominal and pelvic floor muscles can create intra-abdominal pressure which further increases intra-rectal pressure. The [[internal anal sphincter]] (an involuntary muscle) responds to the pressure by relaxing, thus allowing the feces to enter the canal. The rectum shortens as feces are pushed into the anal canal and [[peristalsis|peristaltic waves]] push the feces out of the rectum. Relaxation of the internal and external anal sphincters allows the feces to exit from the anus, finally, as the [[levator ani]] muscles pull the anus up over the exiting feces.
To prevent diseases of the anus{{Fact|date=June 2007}} and to promote general hygiene, humans often clean the exterior of the anus after emptying the bowels. A rinse with water from a [[bidet]] or a wipe with [[toilet paper]] are often used for this purpose.
== Role in sexuality ==
{{main|Anal sex}}
The anus has a relatively high concentration of [[Nerve|nerve ending]]s and is an [[erogenous zone]]. [[Sigmund Freud]]'s theory of [[psychosexual development]], for example, described an [[anal stage]], hypothesizing that toddlers derive pleasure from retaining and expelling feces. This is the source of the term "anal" and the derived, [[derogatory]] vulgarism "[[Anal retentive|anal-retentive]]".
[[Anal sex|Anal intercourse]] can be pleasurable for both the insertive partner and the receptive partner. For the receptive partner, pleasure from anal intercourse is also thought to be related to the shared wall between the rectum and the [[vagina]] (for females) as well as the [[G-spot]] or [[prostate]] (for males). For the insertive partner, the tightness of the anus is often said to be a source of pleasure in penetrative anal sex.
Anal intercourse, sometimes referred to as [[sodomy]] or [[buggery]], is a human sexual activity, but is considered [[taboo]] in a number of moral systems, and it has been, and in some [[jurisdiction]]s continues to be, a crime carrying severe punishment.
Anal sexual activity need not include penetration. The anus also plays an important role in [[facesitting]], [[coprophilia]] and [[Anal-oral contact|anilingus]].
Anal stretching can stimulate the nerves around the anus and can be considered pleasurable. Care must be taken to maintain elasticity.
Lubricant is widely regarded as a necessity while performing anal sex.
==Puberty==
During [[puberty]], as testosterone triggers [[androgenic hair]] growth on the body, pubic hair begins to appear around the anus. Although initially sparse, it fills out by the end of puberty, if not earlier.
==Health==
Hygiene is important for good anal health and anal sex. Washing with a mild soap and water will keep the anus clean. Harsh soaps or wiping vigorously with toilet paper can irritate the skin around the anus, making it itchy or sore. [[Pinworm]]s are sometimes the source of [[Pruritus ani|anal itching]].
Care should be taken not to strip the anus of natural oils that keep the skin around the opening supple and elastic.
Penetration with a penis or [[sex toy]] can irritate or tear the inside of the anus. Lubrication is often recommended to ease penetration. The risk of injury to the anal sphincter should be a concern. Similarly if the anus is torn, this can occasionally cause a [[anal fistula|fistula]] formation which can not only cause fecal leaking, but also can be very difficult to treat.
[[Kegel exercise]]s can improve the tone of the outer sphincter muscle<ref>{{cite web|url=http://www.continence-foundation.org.uk/publications/pdfs/Sphincter%20Exercises%209.PDF|title=The Continence Foundation - Sphincter Exercises to Aid Bowel Control|accessdate=2008-05-14}}</ref>.
==Cosmetics==
Shaving, trimming, [[Hair removal|depilatory]] (hair removal), or [[Brazilian waxing]] can clear the perineum of hair.
[[Anal bleaching]] is a process in which the anus and [[perineum]], which may darken with puberty depending on individual genetics, is lightened for a more youthful appearance. This practice has been linked to skin cancer, and other health problems.
True [[Anal piercing]] is rare because it may interfere with the function of the anus, however surface piercings of the perineum are easier to care for and much more common.
== Pathology ==
Diseases of the anus include [[anal cancer]], [[abscess]], [[wart]]s, [[anal fistula|fistula]], [[anal fissure]], [[itch]]ing and [[hemorrhoid]]. The anus is also a frequent site of [[sexually transmitted infection]]s. These benefit from medical intervention.
[[Birth defects]] of the anus include [[stenosis]] and [[Imperforate anus|imperforation]]. These benefit from surgical intervention.
Damaged [[anal sphincter]] ([[patulous anus]] in more severe cases) — caused by careless or sometimes necessarily sacrificial surgery in the [[Perineum|perineal]] region or by rough/abrupt penetration in [[anal sex]] — can lead to [[flatus]] and/or [[fecal incontinence]], chronic [[constipation]] and, ultimately, [[megacolon]].
In [[psychology]] the [[Sigmund Freud|Freud]]ian term [[anal fixation]] is used.
==Additional images==
<center><gallery>
Image:Gray406.png|Muscles of the male perineum
Image:Gray408.png|Muscles of the female perineum
Image:Gray1077.png|The posterior aspect of the rectum and anus exposed by removing the lower part of the sacrum and the coccyx
</gallery></center>
==See also==
{{wiktionarypar|anus}}
{{commons|Category:Anus|Anus}}
* [[Anal stage]] (Freudian psychosexual stage)
* [[Arse]]
* [[Cloaca]]
* [[Digestive system]]
* [[Flatulence]]
* [[Hemorrhoid]]
* [[Anococcygeal nerve]]
* [[Coccyx]]
* [[Coccydynia|Coccydynia (coccyx pain, tailbone pain)]]
==References==
{{reflist}}
{{digestive system}}
{{human anatomical features}}
{{sex}}
[[Category:Digestive system]]
[[af:Anus]]
[[ar:شرج]]
[[gn:Tevi]]
[[ay:Jamaña]]
[[bs:Anus]]
[[br:Fraezh]]
[[bg:Анус]]
[[ca:Anus]]
[[cs:Řitní otvor]]
[[cy:Anws]]
[[da:Endetarmsåbningen]]
[[de:Anus]]
[[dv:ފުރަގަސް ފަރާތު ދޮރު]]
[[et:Pärak]]
[[es:Ano]]
[[eo:Anuso]]
[[eu:Uzki]]
[[fa:مقعد]]
[[fr:Anus]]
[[ko:항문]]
[[hr:Anus]]
[[io:Anuso]]
[[id:Anus]]
[[iu:ᐃᑎᖅ/itiq]]
[[is:Endaþarmsop]]
[[it:Ano]]
[[he:פי הטבעת]]
[[jv:Anus]]
[[ka:ანუსი]]
[[la:Anus]]
[[lt:Išangė]]
[[ml:മലദ്വാരം]]
[[nl:Anus (anatomie)]]
[[ja:肛門]]
[[no:Anus]]
[[nn:Anus]]
[[pl:Odbyt]]
[[pt:Ânus]]
[[ro:Anus]]
[[ru:Анус человека]]
[[scn:Anu]]
[[simple:Anus]]
[[sk:Ritný otvor]]
[[sl:Zadnjik]]
[[sh:Anus]]
[[su:Kérod salawé]]
[[fi:Peräaukko]]
[[sv:Analöppning]]
[[th:ทวารหนัก]]
[[vi:Hậu môn]]
[[tg:Анус]]
[[tr:Anüs]]
[[zh:肛门]]