Figure 1. The adult foreskin usually covers most or all of the glans. Here, only its outer (true skin) surface is seen. Its inner (mucosal) surface is hidden from view until the foreskin is drawn back (retracted). Note: the infant foreskin is much more protuberant than the adult foreskin.
Figure 2. Erect adult penis. The foreskin adheres to the glans by friction and surface tension. As a result, the foreskin peels (rather than slides) back when it is retracted. Until the foreskin is retracted, the erect penile shaft is covered mainly by shaft skin. However, the scrotum makes an important contribution to the skin covering the base of the penile shaft. The scrotum contracts strongly during erection, thanks to its Dartos muscle. Although it is less obvious in a photograph, Dartos muscle also causes shaft skin and foreskin to contract during erection. This process takes up much of the slack in penile skin resulting from retraction of the foreskin onto the shaft of the penis.
Figure 3. The ridged band is separated from the glans by smooth (non-ridged) mucosa. The arrow points to the boundary between ridged band and true skin of foreskin. Courtesy of the Medical Post.
Figure 4. Foreskin fully retracted. The ridged band is now located further down the shaft of the penis. Note the coarse wrinkling of the outer skin of the foreskin, just above the ridged band (arrowed) in this view. The wrinkling of the foreskin is due to contraction of Dartos muscle elicited by retraction of the foreskin and movement of the ridged band. There is similar but less apparent wrinkling and tightening of shaft skin, also due to contraction of Dartos muscle, within the skin itself.
Figure 5. Frenulum and ridged band. The frenulum is a thin fold of mucosa between the foreskin and glans. It is attached to the midline (raphe) of the glans, very close to the external opening of the urethra (urinary passage). This connection is made possible by the deep notch in the undersurface of the glans. Note: the frenulum blends into the ridged band of the foreskin and this provides a link between several important sensory structures.
Figure 6. Magnified view of part of a ridged band. Special (Meissner) nerve endings embedded in the ridges detect movement of the ridged band and of the adjacent true skin of the foreskin and shaft of penis. Such movement triggers the nerve reflex responsible for ejaculation.
