Try this exercise: Find a 3x5 index card. One side, 15 square inches, equals the average surface area of a man's foreskin — about half of the total surface area of his penis.
Now fold the card in half lengthwise and bring the two short ends together to form a cylinder. The outside of the cylinder represents the external foreskin, a more sensitized, retractable extension of the skin on the penile shaft. The inside represents the delicate, lubricating mucosal lining that sheathes the glans, or head, of the penis.
These outside and inside folds are comparable to the external and internal aspects of the foreskin's closest anatomical analog, the eyelid. And, like the eyelid, the foreskin bristles with nerve endings: about 36% of the total penile allotment.
With this simple overview, you probably already know more about the foreskin than your doctor does. What most American health professionals are taught about it is even more succinct: It's the part of the male anatomy removed in a circumcision.
Despite its highly articulated, specialized physiology, the foreskin is commonly considered as disposable as the paper version you've just created. Every year the foreskins of an estimated 1 million