The foreskin, also called the prepuce (from Latin: prae = in front, putium = penis) is the protective sheath of flesh, which covers the glans, or head of the penis. (Greek: balanos = acorn, Latin: (pl) glandes (pen[i]um) = acorn [of the penis)]). It can be thought of as two portions; the portion of the foreskin that enfolds the glans, beginning at the coronal sulcus is called the "posthe," whereas the visually defining, tapered, fleshy, nipple-like portion of the foreskin that advances past the end of the glans is called the "acroposthion", which is also known as the "overhang."
The skin of the penis is continuous with the foreskin, where it begins to form a cylindrical double layer of tissue consisting of the outer foreskin, which tapers at the acroposthion, whereupon it inverts into itself to become the inner foreskin, which consists of mucous membrane. At the tip of the acroposthion lies a mucocutaneous junction, where the skin of the outer foreskin transitions into the mucosa of the inner foreskin. Both the surface of the glans and the inner foreskin consist of mucous membrane, forming what is called the preputial space. The preputial sphincter functions as the the "drawstring" of the acroposthion, which is formed of a temperature sensitive smooth muscle sheath called the dartos muscle.
Within the preputial space, the inner foreskin is attached to the underside of the glans by a web-like membrane called the frenulum (Latin: fraenum = bridle]). The inner surface of the foreskin consists of two zones, 'ridged' and 'smooth'. The first, a transversely ridged band of mucosa 10-15 mm wide, lies along the mucocutaneous junction, forming the outer surface of the tip of the foreskin. In the dorsal midline, the 'ridged band' lies above the level of the adjacent 'smooth' mucosa and merges smoothly, on either side, with the frenulum an the underside of the glans. When magnified, the ridged mucosa has a pebbled or coral-like appearance.
Upon erection, the foreskin may retract and unroll of itself into a single layered cylinder, but not necessarily, and can usually be retracted manually. Unretracted, the adult 'ridged band' usually lies flat against the glans; retracted, the 'ridged band' is everted onto the shaft of the penis. The remainder of the preputial lining between the 'ridged band' and the glans is smooth and lax. Complex touch-sensitive nerve endings, called Meissner's corpuscles, were found in these ridges. The ridged band is primarily sensory tissue, and rolling over the corona of the glans, provides primary sexual stimulation.
Retraction of the Foreskin
In adult men, the foreskin can usually be retracted to expose the glans with ease. In some cases, the foreskin is tight, retracting with difficulty, while in other cases, it does not retract at all. A condition where the foreskin has trouble retracting, if at all, is often called phimosis (Greek: muzzling), though this diagnosis may be erroneous. (Please see article on phimosis.)
The rare condition of difficulty in retracting the foreskin in adult men must not be confused with the natural state of the penis in neonates and pre-pubecent boys. In newborns and young children, the foreskin is adhered to the glans by means of a membrane called synechia, also known as the balano-preputial membrane or balano-preputial lamina and will not retract. Forcibly retracting the foreskin of a child can cause damage to a child's penis. (Please see article on forced retraction.)
For more on foreskin retraction, please see the article on the Retraction of the Foreskin.
Importance in Sexual Intercourse
”The prepuce is a common anatomical structure of the male and female external genitalia of all human and non-human primates; it has been present in primates for at least 65 million years, and is likely to be over 100 million years old, based on it commonality as an anatomical feature in mammals”. Christopher j. Cold, M.D., and John R. Taylor, M.D. 
In mammals, it is known that the male prepuce is important for normal copulatory function. The neuroanatomy of the prepuce forms a complex sensory platform that is important for normal sexual behavior. In the human penis, the prepuce is known to have ten times as many corpuscular sensory receptors as the glans penis. Surgical removal of the prepuce disturbs normal copulatory behavior in male mammals, and similarly alters sexual behavior in humans.
What is the Foreskin?
What is the foreskin? is a question that many Americans would have trouble answering. Information about the foreskin is virtually absent during discussions of anatomy in biology classrooms, and yet, the foreskin provides a well-documented set of crucial sensory, protective, immunological, hygienic, and sexual functions. The foreskin is a double fold of skin that is twice as big as its appearance. It can make up to 80% or more of the penile skin covering, and includes around 12-20 square inches of skin (the size of a 3x4 or a 4x5 index card).   , and in turn includes a specialized sheet of dartos muscle which can produce sustained contractions of great force that stimulate not only the foreskin but also the glans.  One of the functions of this mobile skin system is to glide up and down the shaft of the penis in order to facilitate non-abrasive stimulation during sexual activity without any need for artificial factory made lubricant. This frictionless gliding mechanism is the principal source of stimulation for the intact penis and facilitates non-abrasive intercourse. 
The neuro-anatomy of the penis has been rigorously studied by respected anatomists of all kinds. The component tissues that comprise the foreskin are richly innervated with the greatest quantity and variety of sensory nerve endings than any other part of the penis; the foreskin can discern the slightest pressure, the lightest touch, the smallest motion, the subtlest changes in temperature, and the finest gradations in texture.          Many people are surprised to discover that the glans or “head” of the penis is actually the least sensitive part and is insensitive to light tough, heat, cold and even pin-pricks.    Permanent unnatural exposure of the penis further desensitizes the glans, the foreskin keeps the glands healthy, clean, shiny, warm, soft, moist, and sensitive; without the foreskin the glans are scared, dry, cracked, and pitted. Most notably, circumcision drastically reduces the glans sensitivity to vibration. 
To no surprise, this information was corroborated in a 2006 study which measured the sensitivity of all the parts of the penis. Researchers used an extremely sensitive pressure sensing probe while each test subject, whose view was blocked with a screen, reported a sensation of touch. To demonstrate precision they took each measurement multiple times. The results were statistically significant (P<0.05). They concluded:
"Five locations on the uncircumcised penis that are routinely removed at circumcision were more sensitive than the most sensitive location on the circumcised penis[...] The glans in the circumcised male is less sensitive to fine-touch pressure than the glans of the uncircumcised male[...]The most sensitive location on the circumcised penis is the circumcision scar on the ventral surface [...] When compared to the most sensitive area of the circumcised penis, several locations on the uncircumcised penis that are missing from the circumcised penis were significantly more sensitive." 
Immunological and Hygienic Function
The foreskin, like the eyelid, also serves an important set of protective and immunological functions. The foreskin protects the delicate glans of the penis and puts the urethra at a distance form its environment, protecting it from foreign contaminants of all kinds while simultaneously shielding the penis from injury. The foreskins inner fold and the glans of the penis are comprised of mucous membrane tissue. These are also present in your eyes, mouth, and all other bodily orifices including the female genitals. These mucous membranes perform many immunological and hygienic functions. Certain components such as Langerhans cells  , plasma cells  , apocrine glands  , and sebaceous glands  , collectively secrete emolliating lubricants  rich in enzymes such as lysosomal enzymes, chymotrypsin, neutrophil elastase, immunoglobulin, cytokine  , cathepsin B  , and langerin which kills the HIV virus  , all these substances function to sequester and “digest” foreign pathogens. The foreskin is also responsible for the production, retention, and dispersal of pheromones such as androsterone  . In time we will discover even more information about the foreskin and its functional components.
The intact penis is naturally clean and maintains a level of hygiene that is optimal when compared to a penis that has been altered by circumcision. In fact, a myriad of rigorously controlled studies performed by objective researchers among racially and socioeconomically homogeneous study groups in developed urban settings have shown that circumcision is often associated with an increased risk of bacterial infections, viral infections, and major STD’s, or no significant difference.            
Needless to say, circumcised men have been denied normal bodily functions associated with anatomically correct genitalia.
- ↑ Hodges FM. Phimosis in antiquity. World J Urol 1999;17(3):133-6.
- ↑ Hodges FM. .The Ideal Prepuce in Ancient Greece and Rome: Male Genital Aesthetics and Their Relation to Lipodermos, Circumcision, Foreskin Restoration, and the Kynodesme. Bull. Hist. Med., 2001 Fall; 75(3): 377-378.
- ↑ Translation adapted from Rufus of Ephesus, Des noms des parties du corps humain 102, in Oeuvres de Rufus d'Éphèse, ed. Charles Daremberg and Charles Émile Ruelle (Paris: L'Imprimerie Nationale, 1879), p. 146.
- ↑ 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.
- ↑ Gairdner D. The fate of the foreskin: a study of circumcision. Br Med J 1949;2:1433-7.
- ↑ Cold CJ, Taylor JR. The prepuce. BJU Int 1999 Jan;83:34-44. [here, p.34]
- ↑ Cold, Christopher; McGrath, Kenneth (1999). "Anatomy and histology of the penile and clitoral prepuce in primates". Male and female circumcision: medical, legal, and ethical considerations in pediatric practice. New York. ISBN 0306461315. http://www.cirp.org/library/anatomy/cold-mcgrath/.
- ↑ Taylor, J.R.; A.P. Lockwood and A.J. Taylor (1996-2). "The prepuce: Specialized mucosa of the penis and its loss to circumcision". British Journal of Urology International 77: 291-95. PMID 8800902. http://www.cirp.org/library/anatomy/taylor/.
- ↑ Cold, C; Tarara R. (1997). "Penile and clitoral prepuce mucocutaneous receptors in macaca mulatta". Vet Pathol 34 (506).
- ↑ Desrochers, A; St. Jean G, Anderson DE. (1986-1996). "Surgical management of preputial injuries in bulls: 51 cases". Can Vet J 1995 (36): 553-6.
- ↑ Lumia, AR; Sachs BD, Meisel RL (August 1979). "Sexual reflexes in male rats: restoration of ejaculation following suppression by penile sheath removal". Physiology & Behavior 23 (2): 273-7.
- ↑ Laumann, EO; Masi CM, Zuckerman EW. (April 2, 1997). "Circumcision in the United States: prevalence, prophylactic effects,and sexual practice.". Journal Of The American Medical Association 277 (13): 1052-7. http://www.cirp.org/library/general/laumann/.
- ↑ Money, J; Davison J (1983). "Adult penile circumcision: erotosexual and cosmetic sequelae". The Journal of Sex Research 19: 298-92. http://www.cirp.org/library/complications/money/.
- ↑ See photographic series in: lander MM. The Human prepuce. In: Denniston GC, Milos MF (eds). Sexual Mutilations: a human Tragedy. New York: Plenum Press; 1997. pp.79-81.
- ↑ 15.0 15.1 15.2 Taylor JR, Lockwood AP, Taylor AJ. The prepuce: specialized musocsa of the penis and its loss to circumcision. Br J Urol 1996 Feb;77(2): 291-5.
- ↑ Jefferson G. The peripenic muscle; some observations on the anatomy of phimosis. Surgery, Gynecology and Obstetrics 1916 Aug;23(2):177-81.
- ↑ K. O'Hara and J. O'Hara. The effect of male circumcision on the sexual enjoyment of the female partner. BJU International, Volume 83, Supplement 1, Pages 79-84, January 1, 1999.
- ↑ Moldwin RM, Valderrama E. Immunohistochemical analysis of nerve distribution patterns within preputial tissues. J Urol 1989 Apr;141(4):499A. (abstract).
- ↑ Dogiel AS. Die Nervenendigungen in der Schleimhaut der asseren Genitalorgane des Menschen. [The nerve endings in the afferent mucosa of the human genital organs.] Arch f. mkr. Anat. 1893; 41: 585-612.
- ↑ Bazett HC, McGlone B, Williams RG, Lufkin HM. Depth, distribution and probable identification in the prepuce of sensory end-organs concerned in sensations of temperature and touch; thermometric conductivity. Archives of Neurology and psychiatry 1932 Mar; 27(3):489-517.
- ↑ Ohmori D. Über die Entwicklung der Innervation der Genital Apparatus als peripheren Aufnahme-Apparat der genitalen Reflex. [The development of innervation of the genital apparatus as peripheral receptors for the genital reflex.] Ztschr. f. d. Ges. Anat. up Entw. 1924; 70: 347-410.
- ↑ Winkelmann RK. The Cutaneous Innervation of the human newborn prepuce. Invest Dermatol 1956 Jan;26(1):53-67.
- ↑ Winkelmann RK. The erogenous zones: their nerve supply and significance. Mayo Clin Proc 1959;34(2):39-47.
- ↑ 24.0 24.1 Halata Z, Munger BL. The neuroanatomical basis for the protopathic sensibility of the human glans penis. Brain Res 1986 Apr23;371(2):205-30.
- ↑ 25.0 25.1 25.2 Morris L. Sorrells, James L. Snyder. Fine-touch pressure thresholds in the adult penis. BJU Int. 2007 Apr;99(4):864-9. http://www.nocirc.org/touch-test/bju_6685.pdf
- ↑ Yang, DM; Lin H, Zhang B, Guo W (April 2008). "Circumcision affects glans penis vibration perception threshold". Zhonghua Nan Ke Xue 14 (4): 328–330.
- ↑ Weiss GN, Sanders M, Westbrook KC. The distribution and density of Langerhans cells in the human prepuce: site of diminished immune response? Isr J Med Sci 1993 Jan;29(1);42-3.
- ↑ Flower PJ, Ladds PW, Thomas AD, Watson DL. An immunopathologic study on the bovine prepuce. Vet Pathol 1983 Mar;20(2):189-201.
- ↑ Ahmed A, Jones AW. Apocrine Cystadenoma: a report of two cases occurring on the prepuce. Br J Dermatol 1969 Dec; 81(12):899-901.
- ↑ Hyman AB, Brownstien MH. Tyson's "glands": ectopic sebaceous glands and papillomatosis penis. Arch Dermatol 1969 Jan;99(1):31-6.
- ↑ Parkash S, Jeykumar S, Subramanyan K, Chaudhuri S. Human Subpreputial collection: its nature and formation. J Urol 1973 Aug 110(2):211-2.
- ↑ Ahmed AA, Nordlind K, Schultzberd M, Liden S. Immunohisto chemical localization of IL-1 alpha-, IL-1 beta-, IL-6- and TNF-alpha-like immunoreactivities in human apocrine glands Arch
- ↑ Frohlich E Shamburg-Lever G, Klesses C. Immunelectron microscopic localization of cathepsin B in human apocrine glands. J Cutan Pathol 1993 Feb;20(1):54-60.
- ↑ de Witte L, Nabatov A, Pion M, et al. Langerin is a natural barrier to HIV-1 transmission by Langerhans cells. Nat Med 2007 Mar;13(3):367-71.
- ↑ Cohn BA. In search of human skin pheromones. Arch Dermatol 1994 Aug; 130(8):1048-51
- ↑ Dermatol Res 1995;287(8):764-6Smith GL, Greenup R, Takafuji ET. Circumcision as a risk factor for urethritis in racial groups. AM J Public Health 1987 Apr;77(4):452-4.
- ↑ Bassett I, Donovan B, Bodsworth NJ. Male circumcision and common sexually transmissible diseases in a developed nation setting. Genitourin Med 1994 Oct;70(5):317 -20.
- ↑ Bassett I, Donovan B, Bodsworth NJ, Field PR, Ho DW, jeansson S, Cunningham AL. Herpes Simplex virus type 2 infection of heterosexual men attending a sexual health sentre. Med J Aust 1994 Jun 6:160(11);697-700.
- ↑ Van Howe R. Does Circumcision Influence Sexually Transmitted diseases?: a literature review. BJU Int 1999 Jan;83 Suppl 1:52-62.
- ↑ Laumann EO, Masi CM, Zuckerman EW. Circumcision in the United States: prevalence, prophylactic effects, and sexual Practice. JAMA 1997 Apr2;277(13):1052-7.
- ↑ Dickson NP, Van Rood T, Herbison P, Paul C. Circumcision and risk of sexually transmitted infections in a birth cohort. J Pediatr 2008;152:383-7.
- ↑ Cook LS, Koutsky LA. Holmes KK. Clinical presentation of genital warts among circumcised and uncircumcised heterosexual men attending an urban STD clinic. Genitourin Med 1993 Aug;69(4):262-4.
- ↑ Van Howe, Robert S. (May 2007). "Human papillomavirus and circumcision: A meta-analysis". Journal of Infection 54 (5): 490–496.
- ↑ Dinh, T.H.; M. Sternberg, E.F. Dunne and L.E. Markowitz (April 2008). "Genital Warts Among 18- to 59-Year-Olds in the United States, National Health and Nutrition Examination Survey, 1999–2004". Sexually Transmitted Diseases 35 (4): 357–360.
- ↑ Van Howe, R.S. (January 1999). "Circucmsion and HIV infection: review of the litarature and meta-analysys". International Journal of STD's and AIDS 10: 8–16.
- ↑ Amir J. et al. Circumcision and Urinary Tract Infections in Infants. Am J Dis Child (1986), vol. 140, p. 1092.
- ↑ Prais D. Shoov-Furman R, Amir J. Is circumcision a risk factor for neonatal urinary tract infections? Arch Dis Child Published Online First: 6 October 2008.