How Big Is The Foreskin?

by Paul M. Fleiss, M.D., Frederick M. Hodges

(Page 2 of 5)

The foreskin is the largest part of the skin system of the penis. It covers and usually extends far beyond the glans before folding under itself to its circumferential point of attachment just behind the corona (the rim of the glans). The foreskin is, therefore, a double-layered organ. Its true length is twice the length of its external fold and comprises as much as 80 percent or more of the penile skin covering. In children, the foreskin often runs to impressive lengths, frequently representing over three quarters of the length of the penis.

If the average adult foreskin were unfolded and laid flat and unstretched, it would be approximately the size of a 3 x 5 index card. Moderately stretched, it would entirely cover a man's forehead or the back of his hand and fingers. That's a lot of skin!

Does The Foreskin Have Muscles?

Yes. The foreskin, like the rest of the penile skin system and scrotum, is lined with the dartos muscle sheet. It is also called the peripenic muscle because it wraps around (peri) the penis (-penic). This remarkably powerful muscle is composed of smooth muscle fibers that run parallel to the shaft of the penis. The dartos muscle is involuntary and highly responsive. It contracts and relaxes in response to touch, temperature, and sexual excitement.

The dartos muscle is always in a state of tonus, or partial contraction-a condition of tension or readiness to contract or relax. The contractions of the dartos muscle are slow, sustained, and may produce great force, such as in cold temperatures.

What Are Eversion And Reversion?

Eversion is the natural mechanical process by which the lips of the foreskin open and allow the foreskin to unroll and slide down the shaft of the penis to reveal the glans. When fully everted, the inner fold of the foreskin that embraces the glans is turned inside-out and moves along the shaft of the penis. Reversion is the reverse process that rolls the foreskin back up the shaft of the penis to cover the glans. Following eversion, the elastic skin system of the penis will usually have a tendency to return to its normal position, re-covering the glans and pursing the lips of the foreskin. Reversion is accomplished through the springlike action of the frenulum.

What Is Unique About The Preputial Orifice?

At the very end of the foreskin lies the rose-colored preputial orifice, also known as the lips of the foreskin. Here, the muscle fibers form a kind of sphincter that ensures optimum protection of the urinary tract from contaminants of all kinds. This functions similarly to the sphincter that closes and purses the lips of your mouth.

In terms of sensitivity, the lips of the foreskin are probably even more sensitive than the lips of the mouth in their ability to detect subtle differences in temperature, pressure, motion, and touch. The orifice remains closed most of the time, but can open up to allow the passage of urine. Thanks to its highly elastic nature, the preputial sphincter can easily and comfortably dilate over ten times its normal diameter to allow the glans to protrude.

What Is Special About the Inner Surface of the Foreskin?

Like the undersurface of the eyelids or the inside of the cheek, the undersurface of the foreskin is lined with a rich red-colored mucous membrane. It is divided into two distinct zones: the smooth mucosa and the ridged mucosa. The smooth mucosa lies against the glans penis. Here, researchers have discovered apocrine and ectopic sebaceous glands that secrete emollients, lubricants, and protective antibodies. Similar glands are found in the eyelids and mouth.

About the Author

PAUL M. FLEISS, M.D., lives in Los Angeles, California.

FREDERICK M. HODGES, D.Phil, lives in New Haven, Connecticut.