: anuses or ani; from Latin ānus, "ring", "circle")[1][2] is the external opening of the rectum located inside the intergluteal cleft.

The anus is the final part of the gastrointestinal tract, and directly continues from the rectum, passing through the pelvic floor.

The top and bottom of the anus are surrounded by the internal and external anal sphincters, two muscular rings which control defecation.

The internal anal sphincter (an involuntary muscle) responds to the pressure by relaxing, thus allowing the feces to enter the canal.

[9] Generally, fissures are due to injury to the mucosa, or because of a poor local blood supply that prevents proper healing, with spasm of the external anal sphincter contributing.

[9] The external anal sphincter can be relaxed by the application of glyceryl trinitrate creams, and constipation is managed with laxatives and improving hydration.

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.

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.

[13] The anus has a relatively high concentration of nerve endings and can be an erogenous zone, which can make anal intercourse pleasurable if performed properly.

[19] Lubricant and condoms are widely regarded as a necessity while performing anal sex, as well as a slow and cautious penetration.

[20] Anal intercourse is sometimes referred to as sodomy or buggery, and is considered taboo in a number of legal systems.

A rinse with water from a bidet or a wipe with toilet paper is often used for this purpose, though anal cleansing practices vary greatly between cultures.

The anus has many slang terms including asshole, butthole (and their respective British equivalents arsehole, bumhole), cornhole, and bunghole.