Foreskin

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Foreskin
A penis with the foreskin covering the glans.
Latin prepucium, præputium
Gray's subject #262 1250
Artery Dorsal artery of the penis
Vein Superficial dorsal vein of the penis
Nerve Dorsal nerve of the penis
Precursor Genital tubercle, Urogenital folds
MeSH Foreskin

The foreskin or prepuce (a technically broader term that also includes the clitoral hood, the homologous structure in women) is a retractable double-layered fold of skin and mucous membrane that covers the glans penis and protects the urinary meatus when the penis is not erect. Contrary to popular belief, it does not always automatically retract during an erection. Almost all mammals have foreskins, although in these 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.[1]

Contents

[edit] The human foreskin

[edit] Description

The Male Anatomy
The Male Anatomy

In humans, the outside of the foreskin is like 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. Like the eyelid, the foreskin is free to move. Smooth muscle fibres keep it close to the glans but make it highly elastic.[2] The foreskin is attached to the glans with a frenulum which helps retract the foreskin over the glans. At the end of foreskin there is a band of tissue called the ridged band which, according to one study, is rich in nerve endings called Meissner's corpuscles.[3] According to a NOCIRC-funded study by Sorrells et al., the five most sensitive areas of the penis are on the foreskin.[4]

In children, the foreskin covers the glans completely but in adults this need not be so. Schöberlein [5] 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).

[edit] Development

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 epithilium (mucous layer) that fuses the two together. It remains this way until the foreskin separates from the glans.[6]

At birth, the foreskin is usually still fused with the glans.[6] As childhood progresses the foreskin and the glans gradually separate, a process that may not be complete until the age of 17.[7] Thorvaldsen and Meyhoff reported that average age of first foreskin retraction in Denmark is 10.4 years.[8] Wright 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.[9] Premature retraction may be painful, and may result in infection.

[edit] Functions

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 to enhance sexual pleasure due to the presence of nerve receptors".[10]

[edit] Sexual

For more details on this topic, see Sexual effects of circumcision.

Taylor et al 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."[11] In 1999, Cold and Taylor stated "The prepuce is primary, erogenous tissue necessary for normal sexual function."[3] Boyle et al, 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—many of which are lost to circumcision, with an inevitable reduction in sexual sensation experienced by circumcised males."[12] The AAP noted that the work of Taylor et al "suggests that there may be a concentration of specialized sensory cells in specific ridged areas of the foreskin."[13]

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."[14] The World Health Organisation states that there is little evidence for diminished sexual function, adding that studies have been inconsistent.[15] Fink et al. 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."[16] Masood et al. state that "[c]urrently no consensus exists about the role of the foreskin or the effect circumcision has on penile sensitivity and overall sexual satisfaction."[17] Schoen 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."[18]

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..."[19] Several opponents of circumcision have argued that the gliding movement of the foreskin is important during sexual intercourse.[20] Warren & Bigelow claim that gliding action would help to reduce vaginal dryness and that restoration of the gliding action is an important advantage of foreskin restoration.[21] O'Hara 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".[22] Taylor suggests that the gliding action, where it occurs, may stimulate the nerves of the ridged band[23], and speculates that the stretching of the frenulum by the rearward gliding action during penetration triggers ejaculation.[24]

Taves used a single subject to test the actual force required to penetrate a measuring apparatus. When the foreskin was retracted a more than tenfold increase in force was needed.[25] He argued that this confirms the belief of Morgan (1967) that the foreskin makes sexual penetration easier during sexual intercourse.[26] Whiddon (1953) and Foley (1966) also believed that the presence of the foreskin made sexual penetration easier.[27][28]

[edit] Other

Gairdner (1949) states that the foreskin protects the glans[6] but some studies show that inflammation of the glans is more common when the foreskin is present.[29]

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,[30] though their theory has been challenged.[31] The American Academy of Pediatrics state that "No controlled scientific data are available regarding differing immune function in a penis with or without a foreskin."[32] Inferior hygiene has been associated with balanitis,[33] though excessive washing can cause non-specific dermatitis.[34]

[edit] Conditions

Frenulum breve is where the frenulum is insufficiently long to allow the foreskin to fully retract, which may lead to discomfort during intercourse. The frenulum may also tear during intercourse. Phimosis is a condition when the foreskin of an adult cannot be retracted properly. (Before adulthood, the foreskin may still be separating from the glans.[35]) Phimosis can be treated by gently stretching the foreskin, by changing masturbation habits,[36] using topical steroid ointments, preputioplasty, or by circumcision.

Non-retractable foreskin is not always indicative of a clinical condition. The first time the foreskin retracts (during masturbation or sex) can be a slightly painful experience as the glans penis is not used to friction and air contact. However the problem gets resolved on its own after a few days of acclimatization, which may include consciously retracting the foreskin and exposing it to air, water or friction.

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.

Aposthia is a rare condition in which the foreskin is not present at birth.

[edit] Surgical and other modifications of the foreskin

Circumcision is the removal of the foreskin, either partially or completely. It may be done for religious, aesthetic, health, or hygiene reasons, or to treat disease.

Preputioplasty is a procedure to relieve a tight foreskin without resorting to circumcision.

Other practices include genital piercings involving the foreskin and slitting the foreskin.[37]

[edit] Research use

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.[38]

[edit] Langerhans cells

Langerhans cells are immature dendritic cells that are found in all areas of the penile epitelium,[39] but are most superficial in the inner surface of the foreskin.[39] The recent Szabo and Short (2000) study 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."[40] 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.[39]However, de Witte et al. (2007) reported that langerin, produced by Langerhans cells, blocks the transmission of HIV to T cells.[41]

[edit] Gallery

Caravaggio's Amor Victorious with the Roman Cupid Amor showing his penis with its foreskin

A penis and foreskin flaccid (left) and semi-erect (right)

A penis with a foreskin

[edit] Foreskin in non-human species

In koalas the foreskin contains naturally occurring bacteria that play an important role in fertilization.[42]

 Please help improve this section by expanding it.
Further information might be found on the talk page or at requests for expansion.


[edit] See also

[edit] References

  1. ^ "Reproductive System". MSN Encarta. (2006). Seattle, WA, USA: Microsoft Corporation. 
  2. ^ Lakshmanan, S; Prakash, S (1980). "Human prepuce - structure & function". Indian J Surg 44: 134-7. 
  3. ^ a b Cold, CJ; Taylor, JR. "The prepuce". BJU Int 83 Supp 1: 34-44. 
  4. ^ 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". BJUINTERNATIONAL 99: 864–869. 
  5. ^ Schöberlein circumcision taboos. Phimosis frenulum and foreskin conditions, phimosis and male initiation
  6. ^ a b c Gairdner, D (1949). "The Fate of The Foreskin: a study of circumcision". BMJ 2: 1433-7. 
  7. ^ Øster, J (1968). "Further fate of the foreskin: incidence of preputial adhesions, phimosis, and smegma among Danish schoolboys". Arch Dis Child 43: 200-3. 
  8. ^ Phimosis: Pathological or Physiological?
  9. ^ 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. 
  10. ^ Male circumcision: Global trends and determinants of prevalence, safety and acceptability 18. World Health Organization.
  11. ^ Taylor, JR; Lockwood, AP; Taylor, AJ (1996). "The prepuce: specialized mucosa of the penis and its loss to circumcision". Br J Urol 77: 291-5. doi:10.1046/j.1464-410X.1996.85023.x. 
  12. ^ Boyle, G; Goldman, R; Svoboda, J; Fernandez E. "Male Circumcision: Pain, Trauma and Psychosexual Sequelae". Journal of Health Psychology 7: 329-343. 
  13. ^ "American Academy of Pediatrics: Circumcision Policy Statement" (March 1999). Pediatrics 103: 686-693. 
  14. ^ Moses S; Bailey RC, Ronald AR (1998). "Male circumcision: assessment of health benefits and risks". Sexually Transmitted Infections Vol 74 (Issue 5): 368-373. “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.” 
  15. ^ Male circumcision: Global trends and determinants of prevalence, safety and acceptability 22. World Health Organization. “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.”
  16. ^ 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. PMID 11956453. 
  17. ^ 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. 
  18. ^ Schoen EJ (December 2007). "Should newborns be circumcised? Yes". Can Fam Physician 53 (12): 2096–8, 2100–2. PMID 18077736. 
  19. ^ Lakshmanan S; Prakash S (1980). "Human prepuce: some aspects of structure and function". Indian Journal of Surgery 44: 134-137. “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.” 
  20. ^ 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” 
  21. ^ Warren, J; Bigelow J (Sep/Oct 1994). "The case against circumcision". Br J Sex Med: 6-8. 
  22. ^ 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, 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.”     
  23. ^ Taylor, J (2000). "Back and Forth". Pediatrics News 34: 50. 
  24. ^ Taylor JR (December 2003). "Evidence sketchy on circumcision and cervical cancer link". Can Fam Physician 49: 1592. PMID 14708921. 
  25. ^ Taves D (August 2002). "The intromission function of the foreskin". Med. Hypotheses 59 (2): 180–2. PMID 12208206. 
  26. ^ Morgan WK (May 1967). ""Penile plunder"". Med. J. Aust. 1 (21): 1102–3. PMID 4226264. 
  27. ^ WHIDDON D (August 1953). "I. Should baby be circumcised?". Lancet 265 (6781): 337–8. PMID 13085774. 
  28. ^ The Unkindest Cut of All
  29. ^ Balanitis and the uncircumcised male
  30. ^ Immunological Functions of the Human Prepuce
  31. ^ STI -- eLetters for Fleiss et al., 74 (5) 364-367
  32. ^ "Circumcision policy statement. American Academy of Pediatrics. Task Force on Circumcision" (March 1999). Pediatrics 103 (3): 686–93. PMID 10049981. 
  33. ^ O'Farrell N, Quigley M, Fox P (2005). "Association between the intact foreskin and inferior standards of male genital hygiene behaviour: a cross-sectional study". Int J STD AIDS 16 (8): 556–9. doi:10.1258/0956462054679151. PMID 16105191. 
  34. ^ Birley: Management of Recurrent Balanitis
  35. ^ Kayaba: Normal Development of the Prepuce
  36. ^ The causes of adolescent phimosis
  37. ^ eMedicine - Paraphimosis : Article by Jong M Choe, MD, FACS
  38. ^ McKie, Robin. "Foreskins for Skin Grafts", The Toronto Star, April 4, 1999. Retrieved on 2008-05-19. 
  39. ^ a b c McCoombe SG, Short RV (2006). "Potential HIV-1 target cells in the human penis". AIDS 20 (11): 1491–5. doi:10.1097/01.aids.0000237364.11123.98. PMID 16847403. 
  40. ^ How does male circumcision protect against HIV infection?. Retrieved on 2007-11-30.
  41. ^ de Witte L, Nabatov A, Pion M, et al (2007). "Langerin is a natural barrier to HIV-1 transmission by Langerhans cells". Nat. Med. 13 (3): 367–71. doi:10.1038/nm1541. PMID 17334373. 
  42. ^ UQ researchers unlock another koala secret

[edit] External links

(WMP, streaming) http://www.doctorsopposingcircumcision.org/video/prepuce.html
(WMP, download) http://www.doctorsopposingcircumcision.org/video/Circumcision_WM7NTSC_256k_D.wmv
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