The foreskin (prepuce) is a retractable, double-layered fold of skin and mucous membrane (the only such example on the human body), and uniquely constructed for its sexual purpose. It covers and protects the head of the penis (glans) and the urinary opening (meatus). Its outer layer is the same as the skin of the shaft of the penis, but the inner layer is mucous membrane, like the inside of the eyelid. The mucous membrane keeps the glans moist, providing a natural lubricant.1
Similar to the eyelid, the foreskin is able to move freely. When not retracted, muscle fibers keep it in position over the glans, but leave it elastic enough to retract backward up the shaft. The foreskin is tethered to the underside of the glans by a highly sensitive strip of tissue (frenulum, or “little bridle”), which helps return the foreskin to its normal position over the glans. The human body has other frenulums, including one under the tongue.
The inner foreskin includes a ring of specialized tissue (ridged band) that is extraordinarily rich in nerve endings. A typical American circumcision removes the most sensitive portions of the penis—all or nearly all of the foreskin and frenulum, and in all cases the entire ridged band—leaving the glans, the least sensitive.2
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