Foreskin

Purpura et al. (2018) describe the foreskin as follows:

"Few parts of the human anatomy can compare to the incredibly multifaceted nature of the human foreskin. At times dismissed as “just skin,” the adult foreskin is, in fact, a highly vascularized and densely innervated bilayer tissue, with a surface area of up to 90 cm, and potentially larger. On average, the foreskin accounts for 51% of the total length of the penile shaft skin and serves a multitude of functions. The tissue is highly dynamic and biomechanically functions like a roller bearing; during intercourse, the foreskin “unfolds” and glides as abrasive friction is reduced and lubricating fluids are retained. The sensitive foreskin is considered to be the primary erogenous zone of the male penis and is divided into four subsections: inner mucosa, ridged band, frenulum, and outer foreskin; each section contributes to a vast spectrum of sensory pleasure through the gliding action of the foreskin, which mechanically stretches and stimulates the densely packed corpuscular receptors. Specialized immunological properties should be noted by the presence of Langerhans cells and other lytic materials, which defend against common microbes, and there is robust evidence supporting HIV protection. The glans and inner mucosa are physically protected against external irritation and contaminants while maintaining a healthy, moist surface. The foreskin is also immensely vascularized and acts as a conduit for essential blood vessels within the penis, such as supplying the glans via the frenular artery."

The following content is part of the Circumpendium.

Anatomy and function of the foreskin in detail

The foreskin covers the glans, thus protecting it from pollutants, friction, injury and drying out. It consists of two superimposed layers, which are only joined together at the very end.

While the outer foreskin layer is an extension of the penile shaft skin, the inner foreskin layer, which lies flat against the glans, is a mucous membrane. The inner layer is an extraordinarily complex tissue. It contains apocrine glands which produce Cathepsin B, lysozymes, chymotrypsin, neutrophil elastase, cytokines and pheromones such as androsterone. Indian scientists have shown that the subpreputial moisture contains lytic material which has an antibacterial and antiviral effect. The natural oils lubricate, moisten and protect the mucous membranes of both the glans and the inner foreskin layer. The tip of the foreskin is supplied with ample amounts of blood through important blood vessels.

The foreskin serves as a pathway for many significant veins. In addition the foreskin is saturated with very many nerve endings and tactile corpuscles, the same receptors that exist in the fingertips. The enormous density of nerves and mechanoreceptors make the foreskin the most sensitive part of the body, approximately 10 times more sensitive than the fingertips. This also distinguishes the human penis from those of other mammals, which in contrast have the main concentration of nerves in the glans, and not in the foreskin.

The two foreskin layers provide a skin reserve, into which the growing shaft expands during an erection. Depending to the individual length of a man's foreskin, it thereby retracts more or less far. In some men, the foreskin still fully covers the glans during an erection, in others the glans is partly or completely exposed.

In addition, the foreskin, in combination with the shaft skin, allows a natural gliding action. During intercourse as well as masturbation the outer skin is in contact with the vagina or the hand respectively. The penile shaft moves mostly within its skin and the skin only moves at the end of its thrust. Due to this, the friction with the vagina or hand is reduced. The sexual stimulation mostly occurs through the stretching and movement of the foreskin, when it is pulled over the glans and back, as well as the direct stimulation of the inner foreskin when it is exposed and comes into direct contact with the vagina or the hand.