Foreskin in Motion
This educational video, Foreskin in motion explains some of the functions of foreskin.
Women have female foreskin that has the same functions and purpose as male foreskin. It is just more commonly called their clitoral hood.
The Foreskin in Motion video reports that the foreskin retracts automatically on erection. This is only partially true. Men with longer, full-length abundant foreskin report the the longer foreskin does not automatically retract on erection, but may be manually retracted.
So what is foreskin?
Contrary to some common misconceptions, the prepuce (foreskin) is not just a double fold of "skin" covering the glans penis. The foreskin is an organ of touch, an anatomically unique structure with its own complex vascular and neural systems and separate attachments to its parts and to the penis. Skin is for containment, attached to the tissue beneath and cannot move independently. The foreskin is the separate and distinct tissues fore (before) the skin of the penile shaft. The following description of the foreskin is that of the flaccid (non-erect) penis as the structural dynamics of the foreskin changes dramatically as the penis proceeds through tumescence to erection.
The foreskin consists of the outer foreskin, an extension of the shaft skin from the back of the sulcus to the foreskin opening, not attached nor part of any other structure which makes the underside of the outer foreskin unique from any other skin found on the body, turns beneath itself at the mucocutaneous juncture where the inner foreskin begins. The inner foreskin mucosa begins at the mucocutaneous junction and is specialized and separate tissue which continues from this junction, traveling between the outer foreskin and the glans, attaching to the penis at the back of the sulcus beneath the end of the shaft skin and beginning of the outer foreskin at the top of the penis (about 10mm to 25mm, 3/8 to 1 inch, behind the back of the glans). The inner foreskin continues toward the glans at the sides and transitions into the frenulum toward the bottom.
The frenulum is the structure traveling down the inner foreskin and connects the inner foreskin to the penis between the hemispheres of the glans below the meatus (urethral opening) at the bottom of the glans and toward the sides and proceeding down the midline of the shaft. Many of the tactile nerve endings of the penis are found in the frenulum. This is similar to the glottal frenulum attaching the tongue to the bottom of the mouth. The ridged band (small corrugations of tissue, like mountain "ridges") are behind the mucocutaneous juncture and when the foreskin is retracted appear behind the attachment at the sulcus. This area also contains many of the tactile nerve endings of the foreskin's neural system.
The foreskin's neural system contains hundreds of feet of nerves and thousands of tactile nerve endings, most of which are concentrated in the frenulum and ridged band. Tactile nerves are sensuous nerves sensitive to pleasant sensations and almost all present in the penis are found within the foreskin. Comparatively, the nerve endings found in the glans are Free Nerve Endings, or nociceptive nerve endings, which are sensitive to cold, pain and unpleasant sensations. The foreskin's vascular system is also quite complex. The blood is supplied by the frenar artery and small and larger veins are present throughout the foreskin and travel down the top of the penis. The abrupt ending of penile veins where they were crushed around the circumference of the penis just behind the area cut off can be seen on a circumcised penis. The tissue and blood vessels over the glans on the top must also be crushed prior to the dorsal cut to prevent hemorrhage and if a circumcision is to be allowed, special care must be taken to thoroughly crush the frenar artery as hemorrhage is very difficult to control.
Coverage and separation
At birth the infant boy's foreskin is almost always fused to his glans as his penis is not fully developed and one protective function of the foreskin is to keep feces and other foreign substances from the meatal opening and the urinary tract of the infant and toddler. That is why the only care for the intact penis is to leave it alone, completely alone. No doctor, nurse, parent or any other care provider should ever investigate, probe or examine his foreskin, especially any forced retraction which will tear foreskin from glans. The undisturbed glans and inner foreskin mucosa is uncontaminated and any such trespasses may introduce that which the foreskin is designed to keep out. His foreskin will naturally separate from his glans and he should be the only one to touch or retract it. When it separates, he will know and he will be retracting his own foreskin. No other person should interfere with this natural process. His foreskin, on average, will represent about 60% to 80% of his penile coverage for additional reasons.
- NSFW: How the foreskin works
- Taylor JR, Lockwood AP, Taylor AJ. The prepuce: specialized mucosa of the penis and its loss to circumcision. Br J Urol. 1996; 77: 291-5. PMID. DOI. Retrieved 23 September 2019.
- Fleiss PM, Hodges FM, Van Howe RS. Immunological functions of the human prepuce. Sex Trans Infect. October 1998; 74(5): 364-67. PMID. Retrieved 12 April 2020.
- Wright JE. Further to the "Further Fate of the Foreskin". Med J Aust. 7 February 1994; 160: 134-135. PMID. Retrieved 12 April 2020.