Human anus

In humans, the anus ( : anuses or ani; from Latin ānus, "ring", "circle") is the external opening of the rectum located inside the intergluteal cleft. Two sphincters control the exit of feces from the body during an act of defecation, which is the primary function of the anus. These are the internal anal sphincter and the external anal sphincter, which are circular muscles that normally maintain constriction of the orifice and which relax as required by normal physiological functioning. The inner sphincter is involuntary and the outer is voluntary. Above the anus is the perineum, which is also located beneath the vulva or scrotum. In part owing to its exposure to feces, a number of medical conditions may affect the anus, such as hemorrhoids. The anus is the site of potential infections and other conditions, including cancer (see anal cancer). With anal sex, the anus can play a role in sexuality. Attitudes toward anal sex vary, and it is illegal in some countries. The anus is often considered a taboo part of the body, and is known by many, usually vulgar, slang terms. Some sexually transmitted infections including HIV/AIDS and anal warts can be spread via anal sex.

In humans, the anus ( : anuses or ani; from Latin ānus, "ring", "circle") is the external opening of the rectum located inside the intergluteal cleft. Two sphincters control the exit of feces from the body during an act of defecation, which is the primary function of the anus. These are the internal anal sphincter and the external anal sphincter, which are circular muscles that normally maintain constriction of the orifice and which relax as required by normal physiological functioning. The inner sphincter is involuntary and the outer is voluntary. Above the anus is the perineum, which is also located beneath the vulva or scrotum. In part owing to its exposure to feces, a number of medical conditions may affect the anus, such as hemorrhoids. The anus is the site of potential infections and other conditions, including cancer (see anal cancer). With anal sex, the anus can play a role in sexuality. Attitudes toward anal sex vary, and it is illegal in some countries. The anus is often considered a taboo part of the body, and is known by many, usually vulgar, slang terms. Some sexually transmitted infections including HIV/AIDS and anal warts can be spread via anal sex. ===Infections=== Anal abscesses usually result from infection of the normal glands of the anus, or sometimes because of Crohn's disease. They usually occur to the sides of the sphincters, and between the internal and external sphincters, either on the surface, or deeper. They may get bigger, enlarging in the direction of the rectum, and resulting in an abnormal connection called an anorectal fistula. They are usually managed with surgical drainage and antibiotics. Additional Sexually transmitted infections Anal warts, also called anal condyloma ===Cancer=== Anal cancer, also called "anal carcinoma", and anal intraepithelial neoplasia. ===Itching, incontinence and constipation=== Itchiness, called pruritus ani, can affect the anus area. It is most often due to long-term exposure of the anus to faeces, with reasons including diseases of the anus such as haemorrhoids, fistulas and fissures; poor hygiene or chronic diarrhoea; local infections such as tapeworm and thrush; or skin conditions such as psoriasis and contact dermatitis. If there is a specific cause identified, the cause may be treated to relieve the itch. Otherwise, treatment includes keeping the area clean and dry, ceasing topical creams and ointments, and potentially bulk-forming laxatives to reduce the chance of faecal contamination. Damage or injury to the anal sphincter (patulous anus in more severe cases) as a result of damage during surgery, such as to the perineal region, or resulting from anal sex; can lead to flatus and/or fecal incontinence, chronic constipation and megacolon. File:Piles Grade 4.svg|A grade IV hemorrhoid protrudes out of the anus. File:1116 Muscle of the Male Perineum.png|Muscles of the male perineum File:1116 Muscle of the Female Perineum.png|Muscles of the female perineum File:Gray1077.png|The posterior aspect of the rectum and anus exposed by removing the lower part of the sacrum and the coccyx File:Raphe1.png|Raphe perinealis of a human female. The raphe perinealis is a fibrous plate of tissue that extends from the anus to the scrotum or vulva. File:Female anus.png|Anus of a dark-skinned female

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