foreskin

The foreskin or prepuce (a technically broader term that also includes the clitoral hood, the analoguous 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. 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]

The human foreskin

Description

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] 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] The foreskin is attached to the glans with a frenulum which helps retract the foreskin over the glans.

In children, the foreskin covers the glans completely but in adults this need not be so. In a German study,^[4] 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).

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.^[5]

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] A Danish survey 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.

Functions

In koalas the foreskin contains naturally occurring bacteria that play an important role in fertilization.^[10] Some also believe that the foreskin has protective and erogenous functions in humans,^[11] though this is disputed. Cold and Tayor stated "The prepuce is primary, erogenous tissue necessary for normal sexual function."^[3] Gairdner states that the foreskin protects the glans^[5] but some studies show that inflammation of the glans is more common when the foreskin is present.^[12]

Morgan wrote that the foreskin's gliding action facilitates sexual intercourse.^[13] Shen (China) found a statistically significant *(p = 0.001) increase in erectile dysfunction following circumcision.^[14] Pang and Kim (South Korea) reported "Of those who were circumcised long after they had been sexually active, > 80% reported no noticeable difference in sexuality, but a man was twice as likely to have experienced diminished sexuality than improved sexuality."^[15] Fink's study of American men also found significantly worsened erectile function *(p = 0.01)^[16] Other studies came to different conclusions. Collins (USA), Senkul (Turkey), and Masood (Britain) found no significant difference in erectile function.^[17][18][19] Senkul found that the circumcised men took significantly longer to ejaculate after circumcision *(P = 0.02).^[19] Laumann's study of American-born men found "little difference between circumcision status and sexual dysfunction for the two younger cohorts" (18-29 and 30-44). However, older men (45-59) with foreskins in his sample were significantly more likely to suffer from erectile dysfunction overall *(p < 0.05) and trouble achieving and maintaining an erection *(p. < 0.05). Premature ejaculation and performance anxiety were also noted *(both p. < 0.10). Circumcision rates were also significantly different in different ethnic groups (less common in Blacks and Hispanics) and they varied with the education level of the mother (less common in those with less education).^[20][21]

Denniston states that the foreskin's innervation provides input to the central and autonomic nervous system to provide erectile function, stimulate ejaculation, and provide pleasure.^[22] Fink's study reported less sensitivity after circumcision, though this only bordered on statistical significance *(p = 0.08).^[16] In contrast, Masood et al. reported improved sensation in 38% of men following circumcision and less sensation in 18%. 61% expressed greater satisfaction following removal of the foreskin, less satisfaction in 17%, and no change in 22%.^[23]

Interpretation of these findings vary. For example, Masood said, "Penile sensitivity had variable outcomes after circumcision. The poor outcome of circumcision considered by overall satisfaction rates suggests that when we circumcise men, these outcome data should be discussed during the informed consent process."^[23] Hill and Denniston listed Senkul's finding of an increased ejaculatory time as a "demonstrated adverse effect" of circumcision^[24] However, Senkul stated: "Adult circumcision does not adversely affect sexual function. The increase in the ejaculatory latency time can be considered an advantage rather than a complication. However, concerning the cause of that increase, in a Muslim community, the psychological influence of circumcision may be more pronounced than the organic effect."

Please see sexual effects of circumcision for more information.

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,^[25] though their theory has been challenged.^[26] Inferior hygiene has been associated with balanitis,^[27] though excessive washing can cause non-specific dermatatis.^[28]

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.^[29]) Phimosis can be treated by gently stretching the foreskin, by changing masturbation habits,^[30] using topical steroid ointments, preputioplasty, or by circumcision. See phimosis for more information.

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.

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.^[31]

Research use

The foreskin, being the part of the male anatomy removed by circumcision, is frequently used by biochemical and micro-anatomical researchers to study the structure and proteins of human skin.

Langerhans cells

The inner surface of the foreskin contains Langerhans' cells with HIV receptors; these cells "must be regarded as the most probable sites for viral entry in primary HIV infection in men."[1]

See also

• Aposthia
• Anatomy
• Circumcision
• Foreskin restoration
• Genitals
• Gliding action
• Langerhans cell
• Dendritic cell
• Masturbation
• Penis
• Preputioplasty
• Ridged band
• Smegma

References

1. ^ Reproductive System - MSN Encarta
2. ^ Lakshmanan/Prakash: Human prepuce - structure & function
3. ^ ^a b The Prepuce: Anatomy, Physiology, Innervation, Immunology, and Sexual Function
4. ^ Schöberlein circumcision taboos. Phimosis frenulum and foreskin conditions, phimosis and male initiation
5. ^ ^a b The Fate of The Foreskin
6. ^ Deibert: Separation of the Prepuce
7. ^ Further Fate of the Foreskin
8. ^ Phimosis: Pathological or Physiological?
9. ^ Further to "The Further Fate of the Foreskin"
10. ^ UQ researchers unlock another koala secret
11. ^ The Children's Hospital at Westmead - Parents - Circumcision
12. ^ Balanitis and the uncircumcised male
13. ^ Penile Plunder
14. ^ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=14979200&query_hl=27
15. ^ http://www.blackwell-synergy.com/doi/abstract/10.1046/j.1464-410X.2002.02545.x?cookieSet=1
16. ^ ^a b Adult Circumcision Outcomes Study: Effect on Erectile Function, Penile Sensitivity, Sexual Activity and Satisfaction
17. ^ Effects of Circumcision on Male Sexual Function: Debunking a Myth?
18. ^ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16037710&query_hl=13
19. ^ ^a b Circumcision in Adults: Effect on Sexual Function
20. ^ Circumcision in the United States
21. ^ Circumcision in the United States: Prevalence, Prophylactic Effects, and Sexual Practice
22. ^ Circumcision in Adults: Effect on Sexual
23. ^ ^a b Penile Sensitivity and Sexual Satisfaction after Circumcision: Are We Informing Men Correctly?
24. ^ JME -- eLetters for Holm, 30 (3) 237
25. ^ Immunological Functions of the Human Prepuce
26. ^ STI -- eLetters for Fleiss et al., 74 (5) 364-367
27. ^ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16105191&query_hl=1&itool=pubmed_docsum
28. ^ Birley: Management of Recurrent Balanitis
29. ^ Kayaba: Normal Development of the Prepuce
30. ^ The causes of adolescent phimosis
31. ^ eMedicine - Paraphimosis : Article by Jong M Choe, MD, FACS

External links

• Foreskin.org - Many detailed pictures of the human male foreskin
• Lakshmanan S., Prakash S. Human prepuce: some aspects of structure and function. Indian J Surg 1980;44:134-7.
• Davenport M. Problems with the penis and prepuce. British Medical Journal 1996;312:299-301.
• Simpson ET, Barraclough P. The management of the paediatric foreskin. Aust Fam Physician 1998;27(5):381-3.
• Cold CJ, McGrath KA. Anatomy and histology of the penile and clitoral prepuce in primates. Male and Female Circumcision 1999
• Video "The Prepuce" a film prepared by Doctors Opposing Circumcision for medical students.

(WMP, streaming) http://www.doctorsopposingcircumcision.org/DOC/prepuce.html

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