Anus

From Encyclopedia of Sex and Sexuality

The point at the lower end of the intestinal tract joining the rectum (which stores feces) with the skin of the buttocks, It is surrounded by the anal sphincter muscles, which contract to allow a person to postpone defecation until a convenient and socially acceptable time and location. The anus also contains sensory nerve endings and, like many other parts of the body, has also been used for sexual stimulation.

Sexual practices involving the anus include anal intercourse, between both heterosexual and homosexual couples, and the insertion of a variety of objects such as dildos and fingers. Heterosexual anal intercourse may be used to prevent pregnancy or to allow the female to remain a “virgin.” Homosexual intercourse is practiced by gay men and in some other cultures as a diversion from heterosexual intercourse. While there is some stimulation of the prostate gland during homosexual anal intercourse, ejaculation usually occurs as a result of masturbation. Anal intercourse is considered by many gay men as signifying a committed relationship, as contrasted with oral sex or mutual masturbation, which may occur in more casual relationships.

Multiple dangers are associated with anal sexual practices. The anal sphincters do not readily dilate to admit the penis or a dildo. Overstretching of the anus can result in the tearing of the anus (anal fissures) or disruption of the anal sphincter muscles. The insertion of foreign objects into the anus carries risk of perforation of the rectum, laceration of the rectal lining, or loss of the object in the rectum, requiring the services of a surgeon for its removal.

The rectum also contains a huge number and variety of bacteria that can enter the urethra or abraded skin of the penis and cause serious infection. In addition, sexually transmitted infections such as syphilis, herpes, and venereal warts have a predilection for growth in the warm, moist environment of the anus. Of even greater concern today is the fear of infection with the AIDS virus, present in both semen and blood. The use of a condom is mandatory if one practices anal intercourse, but it still may not prevent the spread of infection. Furthermore, persons who practice anal receptive intercourse are at a significantly increased risk of developing cancer of the anal canal.