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. For a male insertive partner, the tightness of the anus can be a source of pleasure via the tactile pressure on the penis. Pleasure from the anus can also be achieved through anal masturbation, fingering, fisting, facesitting, anilingus, and other penetrative and non-penetrative acts. 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.
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.
Read more about this topic: Human Anus