A sphincter is a circular muscle that controls the opening of an orifice. The human body has more than 50 types of sphincter muscles including the iris, the esophagus, and the anus.
In anal sex, learning to relax the anal sphincter is important.
The anus and its sphincter muscles are covered in sensitive nerve endings which can bring great pleasure to those who enjoy anal penetration. However, because the sphincter muscles tend to be tighter than vaginal muscles, many men find penetrating an anus especially pleasurable.
Pleasure in anal sex derives from direct stimulation of the anus and of indirect stimulation of the prostate in men and G-spot in women. Rectal tissue is fragile. Unprotected anal sex is considered the riskiest sexual behavior. Generous lubrication and condoms are recommended for all anal intercourse even between long-time partners.
