This educational medical slideshow covers the development and functions of the prepuce(foreskin) from before birth through adulthood. The terminology used while professional is comprehensible to a lay audience.
The ridged band is a ring of deeply corrugated or ridged mucous membrane lining the tip of the prepuce. When the prepuce is retracted, the main part of the ridged band lies across the top and sides of the shaft of the penis. On the underside of the penis, the ridged band merges into the frenulum of the prepuce. Stretching of the accordion-like ridged band triggers important sexual reflexes and erogenous sensation.
It is often assumed that the sole function of the foreskin is to protect the glans. Does recent research support this idea?
The foreskin does protect the glans, but this is not its main function. The foreskin is designed, primarily, to provide light touch, reflex, and erogenous sensory functions. The ridged band is just as important, sexually, as the glans. The foreskin, therefore, does protect the glans but, more importantly, it is designed to protect its own, specialized, mucosal surfaces by turning them inwards, towards the glans.
How does the foreskin compare with the glans as sexual tissue?
The foreskin and the glans have similar functions. Both are designed to trigger nerve impulses that lead to erection and ejaculation. The glans detects deep pressure and movement. The foreskin detects movement through the accordion-like action of the ridged band; in addition, the outer, true skin of the foreskin has an exquisite ability to detect light touch and pin-prick. The glans lacks these abilities because it relies on the covering foreskin to provide them.
What is so special about the ridged band?
The ridged band is part of a muco-cutaneous junctional zone, so called because it lies at the junction between true skin and mucous membrane. Like all such zones, it is equipped with special sensory nerves designed to detect movement. Some junctional zones, such as the lips and eyelids, detect movement through bristle-like hairs. For obvious reasons, the foreskin lacks bristles; instead it is deeply ridged. Its ridges open and close, accordion-like, when the foreskin is stretched. This movement probably helps stimulate motion-sensitive nerve endings in the ridges. Thus the foreskin, lips and eyelids are variants of a basic structural design that differs according to location and type of mechanical stimuli encountered.
How is the foreskin stimulated?
The outside of the foreskin is sensitive to light touch. This sensitivity transmits important information on the general environment of the penis to the brain. The inside layer of the foreskin, especially the ridged band, transmits impulses to the spinal cord which, in turn, transmits impulses to the penis and to the muscle responsible for ejaculation. This is a spinal reflex and, hence, the ridged band is reflexogenic as well as touch-sensitive. The main stimulus to reflex activity appears to be stretching of the ridged band.
How does the foreskin interact with other parts of the penis?
The ridged band, which is mucous membrane (mucosa), is joined directly to the true skin of the penis. The glans, on the other hand, does not come in direct contact with true skin. This arrangement suggests that the ridged band depends for stimulation on the tugging action of penile skin during intercourse. The glans is more independent of penile skin, both functionally and physically.
Does the foreskin allow easy vaginal penetration and a sliding action during intercourse?
The double-layered design of the foreskin does indeed permit smooth penetration and a sliding action. The skin of the penis, including the foreskin, becomes rougher during erection. This roughness is brought about by a mechanism similar to that which raises goosebumps. The extra frictional resistance brought about in this way reduces slippage of penile skin against female tissues. The double-layering of the foreskin is designed to offset the frictional effect of erect penile skin and allow for easy vaginal penetration.