In male human anatomy, the foreskin is a generally retractable double-layered fold of skin and mucous membrane that covers the glans penis and protects the urinary meatus (
/miːˈeɪtəs/) when the penis is not erect. It is also described as the prepuce, a technically broader term that also includes the clitoral hood in women, to which the foreskin is embryonically homologous.
Diagram of a portion of the male anatomy
The outside of the foreskin is a continuation of the skin on the shaft of the penis, but the inner foreskin is a mucous membrane like the inside of the eyelid or the mouth. The mucocutaneous zone occurs where the outer and inner foreskin meet. Like the eyelid, the foreskin is free to move after it separates from the glans, usually by puberty. Smooth muscle fibres keep it close to the glans but make it highly elastic.[1] The foreskin is attached to the glans by a frenulum, which helps return the foreskin over the glans.
The presence of a type of nerve ending called Meissner's corpuscles has been reported. Their density is reportedly greater in the ridged band (a region of ridged mucosa at the tip of the foreskin) than in the larger area of smooth mucosa.[2] They are affected by age: their incidence decreases after adolescence.[3] Meissner's corpucles could not be identified in all individuals.[4] Bhat et al studied Meissner's corpuscles at a number of different sites, including the "finger tips, palm, front of forearm, sole, lips, prepuce of penis, dorsum of hand and dorsum of foot". They found the lowest Meissner's Index (density) in the foreskin, and also reported that corpuscles at this site were physically smaller. Differences in shape were also noted. They concluded that these characteristics were found in "less sensitive areas of the body".[5] In the late 1950s, Winkelmann suggested that some receptors had been wrongly identified as Meissner's corpuscles.[6][7]
The College of Physicians and Surgeons of British Columbia have written that the foreskin is "composed of an outer skin and an inner mucosa that is rich in specialized sensory nerve endings and erogenous tissue."[8]According to a study by Sorrells et al. (2007), the five most sensitive areas of the penis are on the foreskin and the glans is more sensitive in the uncircumcised penis [9]. The study has been criticized by Waskett and Morris, who argue that re-analysis of Sorrells' data shows no significant differences.[10] In 2009, Schober et al reported on self-assessed sexual sensitivity in 81 men, 11 of whom were not circumcised. When assessing areas producing sexual pleasure, the foreskin was ranked 7th, after the glans, lower and upper shaft, and the left and right sides of the penis, but above the area between scrotum and anus, the scrotum itself, and the anus.[11]
Eight weeks after fertilization, the foreskin begins to grow over the head of the penis, covering it completely by 16 weeks. At this stage, the foreskin and glans share an epithelium (mucous layer) that fuses the two together. It remains this way until the foreskin separates from the glans.[12]
At birth, the foreskin is usually still fused with the glans.[12] As childhood progresses the foreskin and the glans gradually separate, a process that may not be complete until late puberty.[13] Thorvaldsen and Meyhoff (2005) reported that average age of first foreskin retraction in Denmark is 10.4 years.[14] Wright (1994) argues that forcible retraction of the foreskin should be avoided and that the child himself should be the first one to retract his own foreskin.[15] Attempts to forcibly retract it can be painful and may injure the foreskin.[16]
In children, the foreskin usually covers the glans completely but in adults, this need not be so. Schöberlein (1966) [17] found that about 50% of young men had full coverage of the glans, 42% had partial coverage, and, in the remaining 8%, the glans was uncovered. After adjusting for circumcision, he stated that, in 4% of the young men, the foreskin had spontaneously atrophied (shrunk). There is considerable variation in the degree to which the foreskin retracts during erection; in some adults the foreskin remains covering the glans until retracted by sexual activity.
The foreskin typically covers the glans when the penis is flaccid (top image), but generally retracts upon erection (bottom image).
The World Health Organization state that there is "debate about the role of the foreskin, with possible functions including keeping the glans moist, protecting the developing penis in utero, or enhancing sexual pleasure due to the presence of nerve receptors".[18]
The Royal Australasian College of Physicians states that the foreskin protects the glans, and that "the foreskin is a primary sensory part of the penis, containing some of the most sensitive areas of the penis. The effects of circumcision on sexual sensation however are not clear, with reports of both enhanced and diminished sexual pleasure following the procedure in adults and little awareness of advantage or disadvantage in those circumcised in infancy."[19] The Royal Dutch Medical Association states that many sexologists view the foreskin as "a complex, erotogenic structure that plays an important role ‘in the mechanical function of the penis during sexual acts, such as penetrative intercourse and masturbation’."[20]
Taylor et al. (1996) described the foreskin in detail, documenting a ridged band of mucosal tissue. They stated: "This ridged band contains more Meissner's corpuscles than does the smooth mucosa and exhibits features of specialized sensory mucosa."[2] In 1999, Cold and Taylor stated: "The prepuce is primary, erogenous tissue necessary for normal sexual function."[21] Boyle et al. (2002) state that "the complex innervation of the foreskin and frenulum has been well documented, and the genitally intact male has thousands of fine touch receptors and other highly erogenous nerve endings."[22] The AAP noted that the work of Taylor et al. (1996) "suggests that there may be a concentration of specialized sensory cells in specific ridged areas of the foreskin."[23]
Moses and Bailey (1998) describe the evidence of sensory function as "indirect," and state that, "aside from anecdotal reports, it has not been demonstrated that this is associated with increased male sexual pleasure."[24] The World Health Organization (2007) states that "Although it has been argued that sexual function may diminish following circumcision due to the removal of the nerve endings in the foreskin and subsequent thickening of the epithelia of the glans, there is little evidence for this and studies are inconsistent."[25] Fink et al. (2002) reported "[a]lthough many have speculated about the effect of a foreskin on sexual function, the current state of knowledge is based on anecdote rather than scientific evidence."[26] Masood et al. (2005) state that "[c]urrently no consensus exists about the role of the foreskin."[27] Schoen (2007) states that "[a]necdotally, some have claimed that the foreskin is important for normal sexual activity and improves sexual sensitivity. Objective published studies over the past decade have shown no substantial difference in sexual function between circumcised and uncircumcised men."[28]
The term 'gliding action' is used in some papers to describe the way the foreskin moves during sexual intercourse. This mechanism was described by Lakshamanan & Prakash in 1980, stating that "[t]he outer layer of the prepuce in common with the skin of the shaft of the penis glides freely in a to and fro fashion..."[29] Several people have argued that the gliding movement of the foreskin is important during sexual intercourse.[30] Warren & Bigelow (1994) state that gliding action would help to reduce the effects of vaginal dryness and that restoration of the gliding action is an important advantage of foreskin restoration.[31] O'Hara (2002) describes the gliding action, stating that it reduces friction during sexual intercourse, and suggesting that it adds "immeasurably to the comfort and pleasure of both parties".[32] Taylor (2000) suggests that the gliding action, where it occurs, may stimulate the nerves of the ridged band,[33] and speculates (2003) that the stretching of the frenulum by the rearward gliding action during penetration triggers ejaculation.[34]
Whiddon (1953), Foley (1966), and Morgan (1967) all believed that the presence of the foreskin made sexual penetration easier.[35][36][37]
Gairdner (1949) states that the foreskin protects the glans.[12] The fold of the prepuce maintains sub-preputial wetness, which mixes with exfoliated skin to form smegma. Some authors believe that smegma contains antibacterial enzymes,[38] though their theory has been challenged.[39] The American Academy of Pediatrics (1999) state that "no controlled scientific data are available regarding differing immune function in a penis with or without a foreskin."[40] Inferior hygiene has been associated with balanitis,[41] though excessive washing can cause non-specific dermatitis.[42]
In primates, the foreskin is present in the genitalia of both sexes and likely has been present for millions of years of evolution.[43] The evolution of complex penile morphologies like the foreskin may have been influenced by females.[44][45][46]
Simmons et al. report that the foreskin's presence "frequently predisposes to medical problems, including balanitis, phimosis, venereal disease and penile cancer", and additionally state that "because we now are able to effectively treat foreskin related maladies, some societies are shifting toward foreskin preservation."[47]
Frenulum breve is a frenulum that is insufficiently long to allow the foreskin to fully retract, which may lead to discomfort during intercourse. Phimosis is a condition where the foreskin of an adult cannot be retracted properly. Before adulthood, the foreskin may still be separating from the glans.[48] Phimosis can be treated by gently stretching the foreskin, by changing masturbation habits,[49] using topical steroid ointments, preputioplasty, or by the more radical option of circumcision. Posthitis is an inflammation of the foreskin.
A condition called paraphimosis may occur if a tight foreskin becomes trapped behind the glans and swells as a restrictive ring. This can cut off the blood supply, resulting in ischaemia of the glans penis.
Lichen sclerosus is a chronic, inflammatory skin condition that most commonly occurs in adult women, although it may also be seen in men and children. Topical clobetasol propionate and mometasone furoate were proven effective in treating genital lichen sclerosus. [50]
Aposthia is a rare condition in which the foreskin is not present at birth.
Circumcision is the removal of the foreskin, either partially or completely. It may be done for religious requirements, health reasons such as to treat a medical disorder, or personal preferences surrounding hygiene and aesthetics. Preputioplasty is a minor procedure designed to relieve a tight foreskin without resorting to circumcision.
Foreskin restoration techniques (developed to help circumcised men 'regrow' a skin covering for the glans by tissue expansion) can be used by men with short foreskins to lengthen the natural foreskin so that it covers the glans. A narrow foreskin may also be widened by tissue expansion.[51]
Other practices include genital piercings involving the foreskin and slitting the foreskin.[52]
Langerhans cells are immature dendritic cells that are found in all areas of the penile epithelium,[53] but are most superficial in the inner surface of the foreskin.[53] A study by Szabo and Short (2000) targets Langerhans cells as receptors of HIV, and states that these cells "must be regarded as the most probable sites for viral entry in primary HIV infection in men."[54] Langerhans cells are also known to express the c-type lectin langerin, which may play a role in transmission of HIV to nearby lymph nodes.[53] However, de Witte et al. (2007) suggested that langerin, produced by Langerhans cells, might block the transmission of HIV to T cells.[55]
Foreskins obtained from circumcision procedures are frequently used by biochemical and micro-anatomical researchers to study the structure and proteins of human skin. In particular, foreskins obtained from newborns have been found to be useful in the manufacturing of more human skin.[56]
Human growth factors derived from newborns' foreskins are used to make a commercial anti-wrinkle skin cream, TNS Recovery Complex.[57]
Foreskins of babies are also used for skin graft tissue,[58][59][60] and for β-interferon-based drugs.[61]
Foreskin fibroblasts have been used in biomedical research.[62]
In koalas, the foreskin contains naturally occurring bacteria that play an important role in fertilization.[63] Almost all mammal penises have foreskins, although in non-human cases the foreskin is usually a sheath into which the whole penis is retracted. Only monotremes (the platypus and the echidna) lack foreskins.[64]
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Composite image showing a penis with the foreskin having been retracted (left), and placed back in usual position covering the glans (right)
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A normal variation in length of the human male foreskin covering the entire glans of a flaccid penis
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A relatively short foreskin which covers most of the glans
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Statue of Gomateshwara which features a penis with a foreskin
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- ^ Lakshmanan, S; Prakash, S (1980). "Human prepuce - structure & function". Indian J Surg 44: 134–7. http://www.cirp.org/library/anatomy/lakshmanan/.
- ^ a b Taylor, JR; Lockwood, AP; Taylor, AJ (1996). "The prepuce: specialized mucosa of the penis and its loss to circumcision". Br J Urol 77 (2): 291–5. DOI:10.1046/j.1464-410X.1996.85023.x. PMID 8800902. http://www.blackwell-synergy.com/doi/pdf/10.1046/j.1464-410X.1996.85023.x.
- ^ Dong, GUO; XU Sheng-mei, JIANG Hai-yang, TAN Ming-bo, LUAN Hua (2007-01). "Observation of Meissner's corpuscle on fused phimosis". Journal of Guangdong Medical College. CNKI:. http://en.cnki.com.cn/Article_en/CJFDTOTAL-GDYY200701004.htm. Retrieved 2010-05-07.
- ^ Haiyang, Jiang; Wang Guxin, Guo Dong, Tan Mingbo, Xu Shengmei (2005-04). "Observation of Meissner's corpuscle in abundant prepuce and phimosis". Journal of Modern Urology. http://en.cnki.com.cn/Article_en/CJFDTOTAL-MNWK200504018.htm. Retrieved 2010-05-07.
- ^ Bhat Gh Mohd, et al (2008). "Density and structural variations of Meissner's corpuscle at different sites in human glabrous skin". J Anat Soc India 57 (1): 30–33. http://medind.nic.in/jae/t08/i1/jaet08i1p30.pdf.
- ^ Winkelmann, R. K. (1956-1). "The cutaneous innervation of human newborn prepuce". Journal of Investigative Dermatology 26 (1): 53–67. DOI:10.1038/jid.1956.5. PMID 13295637. http://www.cirp.org/library/anatomy/winkelmann2/index.html.
- ^ Winkelmann RK (1957). "The mucocutaneous end-organ: the primary organized sensory ending in human skin". AMA Arch Dermatol 76 (2): 225–35. DOI:10.1001/archderm.1957.01550200069015.
- ^ College of Physicians and Surgeons of British Columbia (2009). "Circumcision (Infant Male)" (PDF). https://www.cpsbc.ca/files/u6/Circumcision-Infant-Male.pdf. Retrieved April 22, 2012.
- ^ Sorrels, Morris; James L. Snyder, Mark D. Reiss, Christopher Eden, Marilyn F. Milos, Norma Wilcox and Robert S. Van Howe. (2007). "Fine-touch pressure thresholds in the adult penis" (PDF). Bjuinternational 99 (4): 864–869. DOI:10.1111/j.1464-410X.2006.06685.x. PMID 17378847. http://onlinelibrary.wiley.com/doi/10.1111/j.1464-410X.2006.06685.x/full.
- ^ Waskett, Jake H.; Brian J. Morris (May 2007). "Fine touch pressure thresholds in the adult penis". BJU International 99 (6): 1551–1552. DOI:10.1111/j.1464-410X.2007.06970_6.x. PMID 17537227. http://www3.interscience.wiley.com/cgi-bin/fulltext/118508593/HTMLSTART.
- ^ Schober JM, Meyer-Bahlburg HF, Dolezal C (April 2009). "Self-ratings of genital anatomy, sexual sensitivity and function in men using the 'Self-Assessment of Genital Anatomy and Sexual Function, Male' questionnaire". BJU Int. 103 (8): 1096–103. DOI:10.1111/j.1464-410X.2008.08166.x. PMID 19245445.
- ^ a b c Gairdner, D (1949). "Fate of the Foreskin". BMJ 2 (4642): 1433–7. DOI:10.1136/bmj.2.4642.1433. PMC 2051968. PMID 15408299. http://www.cirp.org/library/general/gairdner/.
- ^ Øster, J (1968). "Further fate of the foreskin. Incidence of preputial adhesions, phimosis, and smegma among Danish schoolboys". Arch Dis Child 43 (228): 200–3. DOI:10.1136/adc.43.228.200. PMC 2019851. PMID 5689532. http://www.cirp.org/library/general/oster/.
- ^ Thorvaldsen MA, Meyhoff H (2005). "Phimosis: Pathological or Physiological?". Ugeskr Læger 167 (17): 1858–62. http://www.cirp.org/library/normal/thorvaldsen1/.
- ^ Wright JE (February 1994). "Further to "the further fate of the foreskin". Update on the natural history of the foreskin". Med. J. Aust. 160 (3): 134–5. PMID 8295581. http://www.cirp.org/library/normal/wright2/.
- ^ "Circumcision of infant males" (PDF). RACP. pp. 7. http://www.racp.edu.au/index.cfm?objectid=65118B16-F145-8B74-236C86100E4E3E8E.
- ^ Schöberlein circumcision taboos. Phimosis frenulum and foreskin conditions, phimosis and male initiation
- ^ "Male circumcision: Global trends and determinants of prevalence, safety and acceptability" (PDF). World Health Organization. pp. 13. http://whqlibdoc.who.int/publications/2007/9789241596169_eng.pdf.
- ^ Paediatrics & Child Health Division, The Royal Australasian College of Physicians (September 2010) (PDF). Circumcision of Infant Males. http://www.racp.edu.au/index.cfm?objectid=65118B16-F145-8B74-236C86100E4E3E8E. Retrieved April 22, 2012.
- ^ "Non-therapeutic circumcision of male minors (2010)". KNMG. 12 June 2010. http://knmg.artsennet.nl/Diensten/knmgpublicaties/KNMGpublicatie/Nontherapeutic-circumcision-of-male-minors-2010.htm.
- ^ Cold, CJ; Taylor, JR. "The prepuce". BJU Int 83 Supp 1: 34–44. http://www.cirp.org/library/anatomy/cold-taylor/.
- ^ Boyle, G; Goldman, R; Svoboda, J; Fernandez E (2002). "Male Circumcision: Pain, Trauma and Psychosexual Sequelae". Journal of Health Psychology 7 (3): 329–343. DOI:10.1177/1359105302007003225. PMID 22114254. http://www.cirp.org/library/psych/boyle6/.
- ^ "American Academy of Pediatrics: Circumcision Policy Statement". Pediatrics 103 (3): 686–693. March 1999. DOI:10.1542/peds.103.3.686. PMID 10049981. http://aappolicy.aappublications.org/cgi/content/full/pediatrics%3b103/3/686.
- ^ Moses S; Bailey RC, Ronald AR (1998). "Male circumcision: assessment of health benefits and risks". Sexually Transmitted Infections 74 (5): 368–373. DOI:10.1136/sti.74.5.368. PMC 1758146. PMID 10195035. http://sti.bmj.com/cgi/reprint/74/5/368. Retrieved 2007-04-28. "There is indirect evidence suggesting that the foreskin may have an important sensory function, although aside from anecdotal reports, it has not been demonstrated that this is associated with increased male sexual pleasure."
- ^ "Male circumcision: Global trends and determinants of prevalence, safety and acceptability" (PDF). World Health Organization. pp. 16. http://whqlibdoc.who.int/publications/2007/9789241596169_eng.pdf.
- ^ Fink KS, Carson CC, DeVellis RF (May 2002). "Adult circumcision outcomes study: effect on erectile function, penile sensitivity, sexual activity and satisfaction". J. Urol. 167 (5): 2113–6. DOI:10.1016/S0022-5347(05)65098-7. PMID 11956453. http://linkinghub.elsevier.com/retrieve/pii/S0022-5347(05)65098-7.
- ^ Masood S, Patel HR, Himpson RC, Palmer JH, Mufti GR, Sheriff MK (2005). "Penile sensitivity and sexual satisfaction after circumcision: are we informing men correctly?". Urol. Int. 75 (1): 62–6. DOI:10.1159/000085930. PMID 16037710. http://www.cirp.org/library/sex_function/masood1/.
- ^ Schoen EJ (December 2007). "Should newborns be circumcised?: YES". Can Fam Physician 53 (12): 2096–8, 2100–2. PMC 2231533. PMID 18077736. http://www.cfp.ca/cgi/pmidlookup?view=long&pmid=18077736.
- ^ Lakshmanan S; Prakash S (1980). "Human prepuce: some aspects of structure and function". Indian Journal of Surgery 44: 134–137. http://www.cirp.org/library/anatomy/lakshmanan/. "The outer layer of the prepuce in common with the skin of the shaft of the penis glides freely in a to and fro fashion and has to be delicate and thin, as was observed in this study. [...] The inner lining of the projecting tubular part has the structure of the outer layer and adds to the thin gliding skin when retracted."
- ^ Kigozi G, Watya S, Polis CB, et al. (January 2008). "The effect of male circumcision on sexual satisfaction and function, results from a randomized trial of male circumcision for human immunodeficiency virus prevention, Rakai, Uganda". BJU Int. 101 (1): 65–70. DOI:10.1111/j.1464-410X.2007.07369.x. PMID 18086100. "Opponents of circumcision, using results from selected observational studies, have argued that the procedure impairs sexual function, and reduces sexual pleasure and satisfaction through keratinization of the glans, removal of the most sensitive preputial tissues, and loss of the 'gliding' mechanism provided by the foreskin"
- ^ Warren, J; Bigelow J (September/October 1994). "The case against circumcision". Br J Sex Med: 6–8. http://www.cirp.org/library/general/warren2/.
- ^ O'Hara K (2002). Sex as Nature Intended It: The Most Important Thing You Need to Know about Making Love, but No One Could Tell You Until Now. Turning Point Publications. pp. 72. "During intercourse, the natural penis shaft actually glides within its own shaft skin covering. This minimizes friction to the vaginal walls and opening, and to the shaft skin itself, adding immeasurably to the comfort and pleasure of both parties.
Friction is not entirely eliminated during natural intercourse but it is largely eliminated. Friction can take place in the lower vagina, but only if the man uses a stroke that exceeds the (forward and backward) gliding range of the shaft's extra skin. And in such a case, there will be friction only to the extent that the shaft exceeded its extra skin, which is uncommon since the natural penis has a propensity for short strokes. Primarily, it is the penis head that makes frictional contact with the vaginal walls, usually in the upper vagina where there is ample lubrication. [...] The gliding principle of natural intercourse is a two-way street—the vagina glides on the shaft skin while the shaft skin massages the penis shaft as it glides over it."
- ^ Taylor, J (2000). "Back and Forth". Pediatrics News 34 (10): 50. http://www.cirp.org/library/anatomy/taylor2/.
- ^ Taylor JR (December 2003). "Evidence sketchy on circumcision and cervical cancer link". Can Fam Physician 49: 1592. PMC 2214164. PMID 14708921. http://www.cfp.ca/cgi/pmidlookup?view=long&pmid=14708921.
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- ^ Fleiss P, Hodges F, Van Howe RS (1998). "Immunological Functions of the Human Prepuce". Sex Transm Inf 74 (5): 364–7. DOI:10.1136/sti.74.5.364. PMC 1758142. PMID 10195034. http://www.cirp.org/library/disease/STD/fleiss3/.
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