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Foreskin

From Wikipedia, the free encyclopedia
This article is about human foreskin. For foreskin in other mammals, see Penile sheath.

Foreskin
Foreskin2.jpg
Foreskin fully covering the glans penis
Details
PrecursorGenital tubercle, urogenital folds
ArteryDorsal artery of the penis
VeinDorsal veins of the penis
NerveDorsal nerve of the penis
Identifiers
LatinPraeputium
MeSHD052816
TA98A09.4.01.011
TA23675
FMA19639
Anatomical terminology

The foreskin is the double-layered fold of smooth muscle tissue, blood vessels, neurons, skin, and mucous membrane part of the penis that covers and protects the glans penis and the urinary meatus.[1] The foreskin is mobile, fairly stretchable, and acts as a natural lubricant. The foreskin 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.

The foreskin of adults is typically retractable over the glans. Coverage of the glans in a flaccid and erect state varies depending on foreskin length. The foreskin is attached to the glans at birth and is generally not retractable in infancy. Inability to retract the foreskin in childhood should not be considered a problem unless there are other symptoms.[2] The highly innervated mucocutaneous zone of the penis occurs near the tip of the foreskin.

The foreskin may become subject to a number of pathological conditions.[3] Most conditions are rare and are easily treated. In some cases, particularly with chronic conditions, treatment may include circumcision, a procedure where the foreskin is partially or completely removed.

Structure

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, which usually occurs before or during puberty. The foreskin is attached to the glans by a frenulum, a highly vascularized tissue of the penis.[4] The World Health Organization states that "[t]he frenulum forms the interface between the outer and inner foreskin layers, and when the penis is not erect, it tightens to narrow the foreskin opening.[4]

The human foreskin contains a sheath of muscle tissue just below the skin, formerly known as the peripenic muscle and now called the dartos fascia, most of which is contained in the foreskin. Elastic fibers are contained in the dartos fascia, which form a whorl at the tip of the foreskin. The whorl of fibers acts as a sphincter in infants, which opens to allow the passage of urine, but closes to protect the glans penis from foreign matter and contaminants. The dartos fascia is sensitive to temperature and expands and contracts with temperature changes. The dartos fascia is only loosely connected with the underlying tissue so it provides the skin mobility and elasticity of the penile skin.[medical citation needed]

According to the histological findings of the British Association of Urological Surgeons based on a research conducted on the autopsy of 22 foreskins, "the prepuce provides a large and important platform for several nerves and nerve endings",[5] The College of Physicians and Surgeons of British Columbia has 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."[6]

Langerhans cells are immature dendritic cells that are found in all areas of the penile epithelium,[7] but are most superficial in the inner surface of the foreskin.[7]

The area of the outer foreskin measures 7–100 cm2,[8] and the inner foreskin measures 18–68 cm.2[9]

In 1996, following a study of 22 cadavers, retired pathologist John Taylor published an influential paper in which he proposed that the pleated skin of the foreskin was a distinct anatomical structure called the "ridged band", and that it played an important role in male sexual function.[10][11] A 2015 review by Cox and colleagues said that the feature was particular to some men and that illustrations of the "ridged band" had been inconsistent in what they pointed to.[12]

Development

The foreskin is present in non-human primates, including the chimpanzee.[4]

Once the foreskin has naturally separated from the glans, the foreskin's two layers of outer skin and inner mucosa can be retracted to reveal the glans and inner foreskin.

In children, the foreskin usually covers the glans completely but in adults it may not. During erection, the degree of automatic foreskin retraction varies considerably; in some adults, the foreskin remains covering all or some of the glans until retracted manually or by sexual activity. This variation was regarded by Chengzu (2011) as an abnormal condition named 'prepuce redundant'. Frequent retraction and washing under the foreskin is suggested for all adults but particularly for those with a long, or 'redundant' foreskin.[13] When the foreskin is longer than the erect penis, it will not spontaneously retract upon erection.

Some males, according to Xianze (2012), may be reluctant for their glans to be exposed because of discomfort when it chafes against clothing, although the discomfort on the glans was reported to diminish within one week of continuous exposure.[14] Guochang (2010) states that for those whose foreskins are too tight to retract or have some adhesions, forcible retraction should be avoided since it may cause injury.[15]

Function

The foreskin typically covers the glans when the penis is not erect (top image), but generally retracts upon erection (bottom image). Coverage of the glans in a flaccid and erect state varies depending on foreskin length.

In 2007 The World Health Organization (2007) said that there was "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".[4] The foreskin helps to provide sufficient skin during an erection.[16]

The foreskin protects the glans.[6] The foreskin protects the glans of infants from ammonia and feces in diapers, which reduces the incidence of meatal stenosis, and continues to protect the glans from abrasions and trauma throughout life.[16] The fold of the prepuce maintains sub-preputial wetness, which can cause smegma when proper hygiene is not performed.[citation needed]

The foreskin contains Meissner's corpuscles, which are nerve endings involved in fine-touch sensitivity. A study of skin samples found that, compared to other hairless skin areas on the body, the Meissner's index was highest in the finger tip (0.96) and lowest in the foreskin (0.28) suggested that the foreskin has the least sensitive hairless tissue of the body.[12] Histological studies research into the sensory properties of the penis have found that the foreskin has "no role in sexual sensation".[17]

Evolution

In primates, the foreskin is present in the genitalia of both sexes and likely has been present for millions of years of evolution.[18] The evolution of complex penile morphologies like the foreskin may have been influenced by females.[19][20][21]

In modern times, there is controversy regarding whether the foreskin is a vital or vestigial structure.[22] In 1949, British physician Douglas Gairdner noted that the foreskin plays an important protective role in newborns. He wrote, "It is often stated that the prepuce is a vestigial structure devoid of function... However, it seems to be no accident that during the years when the child is incontinent the glans is completely clothed by the prepuce, for, deprived of this protection, the glans becomes susceptible to injury from contact with sodden clothes or napkin."[22] During the physical act of sex, the foreskin reduces friction, which can reduce the need for additional sources of lubrication.[22] "Some medical researchers, however, claim circumcised men enjoy sex just fine and that, in view of recent research on HIV transmission, the foreskin causes more trouble than it’s worth."[22] In the March 2017 publication of the Global Health Journal: Science and Practice, Morris and Krieger wrote, "The variability in foreskin size is consistent with the foreskin being a vestigial structure."[23]

Clinical significance

The foreskin can be involved in balanitis, phimosis, sexually transmitted infection and penile cancer.[24] The American Academy of Pediatricians' 2012 technical report on circumcision found that the foreskin tends to harbor micro-organisms that can lead to urinary tract infections in infants and tend to contribute to the transmission of sexually transmitted infections in adults.[25]

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. Phimosis can be treated by using topical steroid ointments and using lubricants during sex; for severe cases circumcision may be necessary.[2] 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 ischemia of the glans penis.[2]

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.[26]

Some birth defects of the foreskin can occur; all of them are rare. In aposthia there is no foreskin at birth,[27]:37–39 in micropathia the foreskin does not cover the glans,[27]:41–45 and in macroposthia, also called and congenital megaprepuce, the foreskin extends well past the end of the glans.[27]:47–50

It has been found that larger foreskins place uncircumcised men at an increased risk for HIV infection[28] most likely due to the larger surface area of inner foreskin and the high concentration of Langerhans cells.[29]

Society and culture

Modifications

See also: Circumcision and Foreskin restoration
Preputioplasty:
Fig 1. Penis with tight phimotic ring making it difficult to retract the foreskin.
Fig 2. Foreskin retracted under anaesthetic with the phimotic ring or stenosis constricting the shaft of the penis and creating a "waist".
Fig 3. Incision closed laterally.
Fig 4. Penis with the loosened foreskin replaced over the glans.

Preputioplasty is the most common foreskin reconstruction technique, most often done when a boy is born with a foreskin that is too small;[30]:177 a similar procedure is performed to relieve a tight foreskin without resorting to circumcision.[30]:181

Circumcision is the removal of the foreskin, either partially or completely. For newborns, it may be done for religious requirements or personal preferences surrounding hygiene and aesthetics.[31]:257 Circumcision may also be performed on children or adults to treat phimosis, balanitis, or to prevent transmission of sexually transmitted infections.[32]:166 The ethics of circumcision in children is a source of controversy.[33][34][35] As of 2012, no successful technique to reconstruct a circumcised foreskin had been published.[30]:181 Some men have used weights to stretch the skin of the penis to regrow a foreskin; the resulting tissue does cover the glans but does not replicate the features of a foreskin.[36]

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

Foreskin-based products

Human neonatal dermal fibroblasts isolated from foreskin stained with calcein-AM. Such cells are commonly used in bioreactor and tissue engineering applications.

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]

Foreskins of babies are also used for skin graft tissue,[39][40][41] and for β-interferon-based drugs.[42]

Foreskin-derived fibroblasts have been used in biomedical research,[43] and cosmetic applications.[44]

Sexual practices

The foreskin can play a role in sexual practices like docking. Docking is a gay sexual practice, which involves mutual masturbation, by inserting the glans penis into the foreskin of another penis.

History

In ancient Greece, foreskins were valued, especially prepuces that were longer in length.[45] The earliest known illustrative depiction of the foreskin dates back to Egyptian kingdoms.[46] The foreskin can be seen depicted in art from different ages.

References

  1. ^ Kirby R, Carson C, Kirby M (2009). Men's Health (3rd ed.). New York: Informa Healthcare. p. 283. ISBN 978-1-4398-0807-8. OCLC 314774041.
  2. ^ Jump up to: a b c "Phimosis (tight foreskin)". NHS Choices. 26 August 2015. Archived from the original on 22 September 2017. Retrieved 21 September 2017.
  3. ^ Shah M (January 2008). The Male Genitalia: A Clinician's Guide to Skin Problems and Sexually Transmitted Infections. Radcliffe Publishing. pp. 37–. ISBN 978-1-84619-040-7. Archived from the original on 2016-02-01. Retrieved 2015-10-27.
  4. ^ Jump up to: a b c d "Male circumcision: Global trends and determinants of prevalence, safety and acceptability" (PDF). World Health Organization. 2007. Archived (PDF) from the original on 2015-07-15. Retrieved 2009-06-12.
  5. ^ Taylor JR, Lockwood AP, Taylor AJ (February 1996). "The prepuce: specialized mucosa of the penis and its loss to circumcision". British Journal of Urology. 77 (2): 291–5. doi:10.1046/j.1464-410X.1996.85023.x. PMID 8800902. Archived from the original on 2019-01-10. Retrieved 2019-01-27.
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  7. ^ Jump up to: a b McCoombe SG, Short RV (July 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. S2CID 22839409.
  8. ^ Kigozi G, Wawer M, Ssettuba A, Kagaayi J, Nalugoda F, Watya S, et al. (October 2009). "Foreskin surface area and HIV acquisition in Rakai, Uganda (size matters)". AIDS. 23 (16): 2209–13. doi:10.1097/QAD.0b013e328330eda8. PMC 3125976. PMID 19770623.
  9. ^ Werker PM, Terng AS, Kon M (September 1998). "The prepuce free flap: dissection feasibility study and clinical application of a super-thin new flap". Plastic and Reconstructive Surgery. 102 (4): 1075–82. doi:10.1097/00006534-199809040-00024. PMID 9734426. S2CID 37976399.
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  12. ^ Jump up to: a b Cox G, Krieger JN, Morris BJ (June 2015). "Histological Correlates of Penile Sexual Sensation: Does Circumcision Make a Difference?". Sexual Medicine. 3 (2): 76–85. doi:10.1002/sm2.67. PMC 4498824. PMID 26185672.
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  17. ^ Bañuelos Marco B, García Heil JL (2020). "Circumcision in childhood and male sexual function: a blessing or a curse?". Int J Impot Res (Review). 33 (2): 139–148. doi:10.1038/s41443-020-00354-y. PMC 7985026. PMID 32994555.
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  23. ^ Morris BJ, Krieger JN, Klausner JD (March 2017). "CDC's Male Circumcision Recommendations Represent a Key Public Health Measure". Global Health: Science and Practice. 5 (1): 15–27. doi:10.9745/GHSP-D-16-00390. PMC 5478224. PMID 28351877.
  24. ^ Simmons MN, Jones JS (May 2007). "Male genital morphology and function: an evolutionary perspective". The Journal of Urology. 177 (5): 1625–31. doi:10.1016/j.juro.2007.01.011. PMID 17437774.
  25. ^ American Academy of Pediatrics Task Force on Circumcision (September 2012). "Male circumcision". Pediatrics. 130 (3): e756-85. doi:10.1542/peds.2012-1990. PMID 22926175.. The technical report was published in conjunction with an updated statement of policy on circumcision: American Academy of Pediatrics Task Force on Circumcision (September 2012). "Circumcision policy statement" (PDF). Pediatrics. 130 (3): 585–6. doi:10.1542/peds.2012-1989. PMID 22926180. S2CID 207166111. Archived (PDF) from the original on 2017-09-01. Retrieved 2017-10-04.
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  28. ^ Van Howe RS, Sorrells MS, Snyder JL, Reiss MD, Milos MF (December 2016). "Letter from Van Howe et al Re: Examining Penile Sensitivity in Neonatally Circumcised and Intact Men Using Quantitative Sensory Testing: Bossio JA, Pukall CF, Steele SS; J Urol 2016;195:1848-1853". The Journal of Urology. 196 (6): 1824. doi:10.1016/j.juro.2016.05.127. PMID 28181790.
  29. ^ Szabo R, Short RV (June 2000). "How does male circumcision protect against HIV infection?". BMJ (Clinical Research Ed.). 320 (7249): 1592–4. doi:10.1136/bmj.320.7249.1592. PMC 1127372. PMID 10845974.
  30. ^ Jump up to: a b c Snodgrass WT (2012). "Chapter 15: Foreskin Reconstruction". In Bolnick DA, Koyle M, Yosha A (eds.). Surgical Guide to Circumcision. London: Springer-Verlag. pp. 177–181. ISBN 978-1-4471-2858-8.
  31. ^ Cox G, Morris BJ (2012). "Chapter 21: Why Circumcision:From Prehistory to the Twenty-First Century". In Bolnick DA, Koyle M, Yosha A (eds.). Surgical Guide to Circumcision. London: Springer-Verlag. pp. 243–259. ISBN 978-1-4471-2858-8.
  32. ^ McClung C, Voelzke B (2012). "Chapter 14: Adult Circumcision". In Bolnick DA, Koyle M, Yosha A (eds.). Surgical Guide to Circumcision. London: Springer-Verlag. pp. 165–175. ISBN 978-1-4471-2858-8.
  33. ^ Boyle G.J., Svoboda J.S., Price C. P., Turner J.N. (2000). "Circumcision of healthy boys: Criminal assault?". Journal of Law and Medicine. 7: 301–310.CS1 maint: multiple names: authors list (link)
  34. ^ "Policy Statement On Circumcision". Royal Australasian College of Physicians. September 2004. Archived from the original (PDF) on 2008-07-20. Retrieved 2007-02-28. The Paediatrics and Child Health Division, The Royal Australasian College of Physicians (RACP) has prepared this statement on routine circumcision of infants and boys to assist parents who are considering having this procedure undertaken on their male children and for doctors who are asked to advise on or undertake it. After extensive review of the literature the RACP reaffirms that there is no medical indication for routine neonatal circumcision. Circumcision of males has been undertaken for religious and cultural reasons for many thousands of years. It remains an important ritual in some religious and cultural groups.…In recent years there has been evidence of possible health benefits from routine male circumcision. The most important conditions where some benefit may result from circumcision are urinary tract infections, HIV and later cancer of the penis.…The complication rate of neonatal circumcision is reported to be around 1% and includes tenderness, bleeding and unhappy results to the appearance of the penis. Serious complications such as bleeding, septicaemia and may occasionally cause death (1 in 550,000). The possibility that routine circumcision may contravene human rights has been raised because circumcision is performed on a minor and is without proven medical benefit. Whether these legal concerns are valid will be known only if the matter is determined in a court of law. If the operation is to be performed, the medical attendant should ensure this is done by a competent operator, using appropriate anaesthesia and in a safe child-friendly environment. In all cases where parents request a circumcision for their child the medical attendant is obliged to provide accurate information on the risks and benefits of the procedure. Up-to-date, unbiased written material summarizing the evidence should be widely available to parents. Review of the literature in relation to risks and benefits shows there is no evidence of benefit outweighing harm for circumcision as a routine procedure in the neonate.
  35. ^ Medical Ethics Committee. British Medical Association. The law and ethics of male circumcision - guidance for doctors; June 2006 [archived 2007-11-12].
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  43. ^ Hovatta O, Mikkola M, Gertow K, Strömberg AM, Inzunza J, Hreinsson J, et al. (July 2003). "A culture system using human foreskin fibroblasts as feeder cells allows production of human embryonic stem cells". Human Reproduction. 18 (7): 1404–9. doi:10.1093/humrep/deg290. PMID 12832363.
  44. ^ Malamut M (14 April 2015). "The 'Baby Foreskin Facial' Is a Real Thing". Boston Magazine.
  45. ^ Hodges, Frederick M. (2001). "The Ideal Prepuce in Ancient Greece and Rome: Male Genital Aesthetics and Their Relation to "Lipodermos", Circumcision, Foreskin Restoration, and the "Kynodesmē"". Bulletin of the History of Medicine. 75 (3): 375–405. doi:10.1353/bhm.2001.0119. JSTOR 44445662. PMID 11568485. S2CID 29580193.
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