Human anus
The human anus (from Latin anūs meaning "ring", "circle")[1][2] is the external opening of the rectum. Like other animals, its closure is controlled by sphincter muscles. Feces are expelled from the body through the anus during the act of defecation, the primary function of the anus.
The anus can play a role in sexuality, though attitudes towards anal sex vary and it is illegal in some countries.[3] The anus is often considered a taboo part of the body,[3] and it is known by a large number of usually vulgar slang terms. The anus is also the site of potential infections and other conditions, including cancer. The traditional polite synonym for anus was fundament, though this euphemism is rarely heard now that medical terms are widely acceptable.
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 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[citation needed] 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, though anal cleansing practices vary greatly between cultures.
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. However, in some ethnicities, androgenic hair is less common.
Sexuality
The anus has a relatively high concentration of nerve endings and is an erogenous zone, which can make anal intercourse pleasurable for both the insertive partner and the receptive partner. 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-retentive" and the derived, derogatory vulgarism "anal".
In addition to nerve endings, pleasure from anal intercourse occurs due to the shared wall between the anus and the prostate for males and vagina/G-Spot for females. This allows for indirect stimulation of the G-Spot or clitoral legs in women, and prostate in men.[4][5][6][7] For a male insertive partner, the tightness of the anus can be a source of pleasure via the tactile pressure on the penis.[6][8] Pleasure from the anus can also be achieved through anal masturbation, fingering, fisting, facesitting, anilingus, and other penetrative and non-penetrative acts.[3] 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.[9][10][11][12]
Anal intercourse is sometimes referred to as sodomy or buggery, and is considered taboo in a number of legal systems. It has been, and in some jurisdictions continues to be, a crime carrying severe punishment.[3]
Health
Hygiene is important for good anal health. 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. Pinworms are sometimes the source of 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 fistula formation which can not only cause fecal leaking, but also can be very difficult to treat.
Sphincter exercise can improve the tone of the outer sphincter muscle.[13]
Cosmetics
Shaving, trimming, 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 after puberty depending on individual genetics, is lightened for a more youthful appearance.
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, warts, fistula, anal fissure, itching and hemorrhoid. The anus is also a frequent site of sexually transmitted infections. These benefit from medical intervention.
Birth defects of the anus include stenosis and 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 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 Freudian term anal fixation is used.
Additional images
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Muscles of the male perineum -
Muscles of the female perineum -
The posterior aspect of the rectum and anus exposed by removing the lower part of the sacrum and the coccyx
See also
- Anal stage (Freudian psychosexual stage)
- Anococcygeal nerve
- Cloaca
- Coccydynia
- Coccyx
- Digestive system
- Flatulence
- Hemorrhoid
References
- ^ Martim de Albuquerque (1873). Notes and Queries. Original from the University of Michigan: Oxford University Press. pp. Page 119.
- ^ An Irish-English Dictionary. Original from Oxford University: J. Duffy. 1864. pp. Page 7.
{{cite book}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ a b c d "Anal Sex". Health.discovery.com. Retrieved 2010-04-23.
- ^ "The male hot spot — Massaging the prostate". Go Ask Alice!. September 27, 2002 (Last Updated/Reviewed on March 28, 2008). Retrieved April 21, 2010.
{{cite web}}: Check date values in:|date=(help) - ^ The Orgasm Answer Guide. JHU Press. 2009. pp. 151 pages. ISBN 0801893968, 9780801893964. Retrieved November 6, 2011.
{{cite book}}: Check|isbn=value: invalid character (help); Cite uses deprecated parameter|authors=(help) - ^ a b See page 3 for women preferring anal to vaginal, and page 15 for reaching orgasm through indirect stimulation of the G-Spot. Tristan Taormino (1997). The Ultimate Guide to Anal Sex for Women. Cleis Press. pp. 282 pages. ISBN 1573442216, 9781573442213. Retrieved November 6, 2011.
{{cite book}}: Check|isbn=value: invalid character (help) - ^ Natasha Janina Valdez (2011). Vitamin O: Why Orgasms Are Vital to a Woman's Health and Happiness, and How to Have Them Every Time!. Skyhorse Publishing Inc. pp. 282 pages. ISBN 1616083115, 9781616083113. Retrieved November 6, 2011.
{{cite book}}: Check|isbn=value: invalid character (help) - ^ Understanding sexual interaction. Houghton Mifflin (Original from the University of Virginia). 1981 (Digitized May 29, 2008). pp. 592 pages. ISBN 0395297249, 9780395297247. Retrieved November 6, 2011.
{{cite book}}: Check|isbn=value: invalid character (help); Check date values in:|date=(help); Cite uses deprecated parameter|authors=(help); horizontal tab character in|publisher=at position 32 (help) - ^ Dr. John Dean and Dr. David Delvin. "Anal sex". Netdoctor.co.uk. Retrieved April 29, 2010.
- ^ Janell L. Carroll (2009). Sexuality Now: Embracing Diversity. Cengage Learning. p. 629. ISBN 0495602744, 9780495602743. Retrieved 2010-12-19.
{{cite book}}: Check|isbn=value: invalid character (help) - ^ Joel J. Heidelbaugh (2007). Clinical men's health: evidence in practice. Elsevier Health Sciences. pp. 608 pages. ISBN 9781416030003. ISBN 141603000X, 9781416030003. Retrieved 2011-10-14.
- ^ Carballo-Diéguez, Alex; Stein, Z.; Saez, H.; Dolezal, C.; Nieves-Rosa, L.; Diaz, F. (2000). "Frequent use of lubricants for anal sex among men who have sex with men" (PDF). American Journal of Public Health. 90 (7): 1117–1121. doi:10.2105/AJPH.90.7.1117. PMID 10897191.
- ^ How the healthy bowel works Continence Foundation.org
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