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Foreskin

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Penis, the foreskin covering (L) and uncovering (R) the glans. (larger version).

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. 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

File:Male anatomy.png
The Male Anatomy
Penis in non-erect state, showing a foreskin that completely covers the glans.

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. 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 the book Sex as Nature Inteded It, author Kristen O'Hara argues that foreskin is a natural gliding stimulator of the vaginal walls during intercourse, increasing a woman's overall clitoral stimulation and allowing for the achievement of female orgasm more often and in shorter periods of time. This is called gliding action. It is believed by many that the absence of the foreskin makes it more difficult, not impossible, for a woman to achieve orgasm during intercourse.

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]

Shen (China) found a statistically significant *(p = 0.001) increase in erectile dysfunction following circumcision.[13] 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."[14] Fink's study of American men also found significantly worsened erectile function *(p = 0.01)[15] Other studies came to different conclusions. Collins (USA), Senkul (Turkey), and Masood (Britain) found no significant difference in erectile function.[16][17][18] Senkul found that the circumcised men took significantly longer to ejaculate after circumcision *(P = 0.02).[18] 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).[19][20]

Fink's study reported less sensitivity after circumcision, though this only bordered on statistical significance *(p = 0.08).[15] 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%.[21]

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."[21] Hill and Denniston listed Senkul's finding of an increased ejaculatory time as a "demonstrated adverse effect" of circumcision[22] 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,[23] though their theory has been challenged.[24] Inferior hygiene has been associated with balanitis,[25] though excessive washing can cause non-specific dermatatis.[26]

Function of gliding action

Gliding action describes the way the foreskin may move during sexual intercourse. The foreskin covers the glans penis but may move back and forth over the glans. The gliding movement of the foreskin may reduce friction during sexual intercourse. This gliding action was described by Lakshamanan & Prakash in 1980 [2]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...

Several genital integrity activists have argued that the gliding movement of the foreskin is important during sexual intercourse.

  • 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. [3]
  • A survey by Bensley & Boyle provides some confirmation that gliding action provides protection of vaginal lubrication.[4] The authors explain, however, that their subjects were self-selected and a larger sample size is needed.
  • O'Hara describes the gliding action:
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. (O'Hara, p.72)
  • Fleiss and Hodges claim: The foreskin's double-layered sheath enables the penile shaft skin to glide back and forth over the penile shaft. (p.24) and The foreskin enables the penis to slip in and out of the vagina nonabrasively inside its own slick sheath of self-lubricating movable skin. (p.26)
  • Taylor suggests that the gliding action, where it occurs, may stimulate the nerves of the ridged band [5], and speculates that the stretching of the frenulum by the rearward gliding action during penetration triggers ejaculation. [6]

In the first study of its kind, Taves tested the actual force required to penetrate, using a single subject, an apparatus designed to measure the force needed. A ten-fold increase in force was observed in the absence of the foreskin.[7] This confirms the belief of Whiddon (1953) and Foley (1966) that the foreskin makes sexual penetration easier during sexual intercourse [8] [9].

Some do not accept that the presence or absence of the foreskin makes any difference. In Babywatching (1991), Desmond Morris claims circumcision "has no effect, one way or the other, on the sexual performance of the adult male", though he does not discuss gliding action specifically. ISBN 0-224-06011-2

A 2002 study into changing circumcision practices in Tanzania Africa, found that there was a significant move towards the popularizing of circumcision, mostly for perceived health reasons, but that participants (unclear whether male focus groups or female as well) reported it also led to improved sexual pleasure for men and women alike. Some participants in this context, compared the presence of a foreskin to a condom.[27]

Schoeberlein (1966) reports that 8.8 percent of young German males aged 18-22 have phimosis [10]. This may prevent the gliding action. He also reported a wide variation in foreskin length. This could also affect the degree or the existence of the gliding action in different individuals.

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.[28]) Phimosis can be treated by gently stretching the foreskin, by changing masturbation habits,[29] 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.[30]


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.[11]

Langerhans cells

Langerhans cells are immature dendritic cells that are found in the inner surface of the foreskin. The recent Szabo and Short 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."[12]

Foreskin in non-human species

Additional images

  • Vertical section of bladder, penis, and urethra.
    Vertical section of bladder, penis, and urethra.

See also

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. ^ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=14979200&query_hl=27
  14. ^ http://www.blackwell-synergy.com/doi/abstract/10.1046/j.1464-410X.2002.02545.x?cookieSet=1
  15. ^ a b Adult Circumcision Outcomes Study: Effect on Erectile Function, Penile Sensitivity, Sexual Activity and Satisfaction
  16. ^ Effects of Circumcision on Male Sexual Function: Debunking a Myth?
  17. ^ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16037710&query_hl=13
  18. ^ a b Circumcision in Adults: Effect on Sexual Function
  19. ^ Circumcision in the United States
  20. ^ Circumcision in the United States: Prevalence, Prophylactic Effects, and Sexual Practice
  21. ^ a b Penile Sensitivity and Sexual Satisfaction after Circumcision: Are We Informing Men Correctly?
  22. ^ JME -- eLetters for Holm, 30 (3) 237
  23. ^ Immunological Functions of the Human Prepuce
  24. ^ STI -- eLetters for Fleiss et al., 74 (5) 364-367
  25. ^ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16105191&query_hl=1&itool=pubmed_docsum
  26. ^ Birley: Management of Recurrent Balanitis
  27. ^ Nnko et al, Dynamics of Male Circumcision Practices in Northwest Tanzania, carried out in the context of the Tanzania-Netherlands project to support AIDS control in Mwanza Region (TANESA) [1]
  28. ^ Kayaba: Normal Development of the Prepuce
  29. ^ The causes of adolescent phimosis
  30. ^ eMedicine - Paraphimosis : Article by Jong M Choe, MD, FACS
(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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