Gynecology Sexual anatomy

foreskin Wikipedia

image:male anatomy.png|thumb|350px|The Male Anatomy
The foreskin or prepuce 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 including marsupials http://www.uq.edu.au/news/?article=2193 and marine mammals http://www.doc.govt.nz/Publications/004~Science-and-Research/DOC-Science-Internal-Series/PDF/DSIS104.pdf have foreskins. Only monotremes http://encarta.msn.com/encyclopedia_761553537_2/Reproductive_System.html (the platypus and the echidna) lack foreskins.

In females, the clitoral hood (see that article), is an analogous structure.

Description
Image:Penis reduced.jpg|thumb|right|250px|An uncircumcised penis in both flaccid and fully erect states, respectively (:Image:Penis corrected.jpg|larger version).

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.http://www.cirp.org/library/anatomy/lakshmanan/ At the end of foreskin there is a band of tissue called the ridged band which is rich in nerve endings called Meissner's corpuscles http://www.cirp.org/library/anatomy/cold-taylor/. 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, http://www.male-initiation.net/library/medicus/schoeberlein.html#start Schoeberlein 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 http://www.cirp.org/library/general/gairdner/.

At birth, the foreskin is usually still fused with the glans http://www.cirp.org/library/anatomy/deibert/. As childhood progresses the foreskin and the glans gradually separate, a process that may not be complete until the age of 17 http://www.cirp.org/library/general/oster/. A Danish survey reported that average age of first foreskin retraction in Denmark is 10.4 years.http://www.cirp.org/library/normal/thorvaldsen1/ 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 http://www.cirp.org/library/normal/wright2/. 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 fertilisation http://www.uq.edu.au/news/?article=2193. Some also believe that the foreskin has protective and erogenous functions in humans http://www.chw.edu.au/parents/factsheets/circumj.htm, though this is disputed. Cold and Tayor stated "The prepuce is primary, erogenous tissue necessary for normal sexual function."http://www.cirp.org/library/anatomy/cold-taylor/ Gairdner states that the foreskin protects the glans http://www.cirp.org/library/general/gairdner/ but some studies show that inflammation of the glans is more common when the foreskin is present.http://www.circs.org/library/waskett3/index.html.

Morgan wrote that the foreskin's gliding action facilitates sexual intercourse http://www.cirp.org/library/general/morgan2/. Shen (China) found a statistically significant *(p = 0.001) increase in erectile disfunction following circumcision. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=14979200&query_hl=27. 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." http://www.blackwell-synergy.com/doi/abstract/10.1046/j.1464-410X.2002.02545.x?cookieSet=1 Fink's study of American men also found significantly worsened erectile function *(p = 0.01)http://www.cirp.org/library/sex_function/fink1/. Other studies came to different conclusions. Collins (USA), Senkul (Turkey), and Masood (Britain) found no significant difference in erectile function http://www.circs.org/library/collins/ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16037710&query_hl=13 http://www.circs.org/library/senkul/. Senkul found that the circumcised men took significantly longer to ejaculate after circumcision *(P = 0.02) http://www.circs.org/library/senkul/. 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). http://www.cirp.org/library/general/laumann/ and http://www.circs.org/library/laumann/.

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.http://www.cirp.org/library/sex_function/denniston3/ Fink's study reported less sensitivity after circumcision, though this only bordered on statistical significance *(p = 0.08). http://www.cirp.org/library/sex_function/fink1/ 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%. http://www.cirp.org/library/sex_function/masood1/

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." http://www.cirp.org/library/sex_function/masood1/ Hill and Denniston listed Senkul's finding of an increased ejaculatory time as a "demonstrated adverse effect" of circumcision http://jme.bmjjournals.com/cgi/eletters/30/3/237#411 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.

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 http://www.cirp.org/library/normal/kayaba/.) Phimosis can be treated by gently stretching the foreskin, 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 ischaemia to the glans penis and is a medical emergency. Applying crushed ice to the affected area may help, but seek medical assistance immediately.

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 http://www.emedicine.com/med/topic2874.htm.

Several of the studies noted in this article refer to statistically significant findings.

Statistical significance is a measure of confidence that an observed association is not due to chance. It is often expressed as a p value, where p stands for the probability that the finding is due to chance. Thus, a lower value of p means a stronger association.

A finding is considered significant if p is less than a certain value, called the significance level. The choice of level is somewhat arbitrary,http://www.itl.nist.gov/div898/handbook/eda/section3/eda35.htm but commonly chosen values are 0.10, 0.05, and 0.01.http://www.stat.yale.edu/Courses/1997-98/101/sigtest.htm http://www.itl.nist.gov/div898/handbook/eda/section3/eda35.htm

A p value of 0.10 means that the probability of the finding occurring by chance is 10% or 1 in 10.

A p value of 0.08 is an 8% probability of a chance occurrence, or one in 12.5

A p value of 0.05 is a 5% probability, or 1 in 20.

A p value of 0.02 is 2%, or 1 in 50

A p value of 0.01 is 1%, or 1 in 100.

A p value of 0.001 is 0.1%, or 1 in 1000.

A finding of statistical significance does not by itself demonstrate that one thing caused another. See also statistical significance http://www.stat.tamu.edu/stat30x/notes/node42.html

• Aposthia

<!-- It is suggested to add medical and anatomical information only. Issues for or against circumcision, or sites advocating one or the other, might belong at Male circumcision but are best avoided here, in the interest of avoiding edit wars.

If really necessary to add circumcision advocacy or anti-advocacy links, they could be put into separate subsections "Pro-circumcision" and "Anti-circumcision"... but again, perhaps this article should concentrate on anatomical description and medical conditions, etc. -->

• Lakshmanan S., Prakash S. http://www.cirp.org/library/anatomy/lakshmanan/ Human prepuce: some aspects of structure and function. Indian J Surg 1980;44:134-7.

Last Modified:   2005-12-19