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In male human anatomy, the foreskin is a double-layered fold of skin and mucous membrane that covers the glans penis and protects the urinary meatus when the penis is not erect. The foreskin is typically retractable over the glans. It 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.

Description
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, usually by puberty. Smooth muscle fibres keep it close to the glans but make it highly elastic. The foreskin is attached to the glans by a frenulum, which helps return the foreskin over the glans.

Taylor et al. (1996) reported the presence of Krause end-bulbs and a type of nerve ending called Meissner's corpuscles. Their density is reportedly greater in the ridged band (a region of ridged mucosa at the tip of the foreskin) than in the larger area of smooth mucosa. They are affected by age: their incidence decreases after adolescence. Meissner's corpuscles could not be identified in all individuals. Bhat et al studied Meissner's corpuscles at a number of different sites, including the "finger tips, palm, front of forearm, sole, lips, prepuce of penis, dorsum of hand and dorsum of foot". They found the lowest Meissner's Index (density) in the foreskin, and also reported that corpuscles at this site were physically smaller. Differences in shape were also noted. They concluded that these characteristics were found in "less sensitive areas of the body". In the late 1950s, Winkelmann suggested that some receptors had been wrongly identified as Meissner's corpuscles.

The College of Physicians and Surgeons of British Columbia have 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."

Development
The development of the foreskin begins approximately eight weeks after fertilization. It appears as a thick epidermis and starts to grow towards the base of the glans penis [SITE DEVEL OF PREPUCE]. At 12 weeks the urethra begins to open on the inferior part of the shaft. The outgrowths of the glans begin to bring the foreskin onward and it begins to form the frenulum. The frenulum is a small fold of the tissue that is involved in the motion of the penis and the part of attachment [site Dictionary]. At 16 weeks the epidermis of the foreskin is connected in a continuous fashion to the epidermis that covers the glans of the penis [Site devel of pre]. Although these are the normal stages of development, the variation in growth is very varied across children. Some children are born with the complete separation of the prepuce while others are born with partial separation or no separation of the prepuce [Site devel of pre].

If the prepuce cannot be separated at birth, then it is considered to be non-retractable. Old advice concerning the prepuce stated that having a foreskin that could retract after age three was extremely important for cleanliness and for reducing the presence of smegma [Site Fate of the foreskin]. In addition, many individuals consider age five to be the age where the majority of boys have a retractable prepuce. It is important to note that a retractable foreskin is not the same as circumcision. Circumcision is the cutting of the foreskin, but a retractable foreskin is characterized by the stretching of the skin.

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 epithelium (mucous layer) that fuses the two together. It remains this way until the foreskin separates from the glans.

At birth, the foreskin is often still fused with the glans. As childhood progresses the foreskin and the glans gradually separate, a process that may not be complete until late puberty. Thorvaldsen and Meyhoff (2005) reported that 21% of 7-year-old boys had non-retractable foreskins, and this number dropped to 7% at puberty, with first retraction at an average age of 10.4 years. Wright (1994) 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. Attempts to forcibly retract it can be painful and may injure the foreskin.

In children, the foreskin usually covers the glans completely but in adults, this need not be so. Schöberlein (1966) 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). There is considerable variation in the degree to which the foreskin retracts during erection; in some adults the foreskin remains covering the glans until retracted by sexual activity.

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 enhancing sexual pleasure due to the presence of nerve receptors". . The foreskin is also thought to protect the glans, which is sensitive tissue, from contamination and irritation from external sources [Source, The Prepuce].

Sexual
Whiddon (1953), Foley (1966), and Morgan (1967) all believed that the presence of the foreskin made sexual penetration easier.

Taylor et al. (1996) 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." In 1999, Cold and Taylor stated: "The prepuce is primary, erogenous tissue necessary for normal sexual function." Boyle et al. (2002) 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." The AAP noted that the work of Taylor et al. (1996) "suggests that there may be a concentration of specialized sensory cells in specific ridged areas of the foreskin."

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." The World Health Organization (2007) states that "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." Fink et al. (2002) reported "although 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." Masood et al. (2005) state that "currently no consensus exists about the role of the foreskin." Schoen (2007) states that "anecdotally, 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."

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..." Several people have argued that the gliding movement of the foreskin is important during sexual intercourse. Warren & Bigelow (1994) state that gliding action would help to reduce the effects of vaginal dryness and that restoration of the gliding action is an important advantage of foreskin restoration. O'Hara (2002) 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". Taylor (2000) suggests that the gliding action, where it occurs, may stimulate the nerves of the ridged band, and speculates (2003) that the stretching of the frenulum by the rearward gliding action during penetration triggers ejaculation.

The Royal Australasian College of Physicians states that the foreskin protects the glans, and that "the foreskin is a primary sensory part of the penis, containing some of the most sensitive areas of the penis. The effects of circumcision on sexual sensation however are not clear, with reports of both enhanced and diminished sexual pleasure following the procedure in adults and little awareness of advantage or disadvantage in those circumcised in infancy." The Royal Dutch Medical Association (2010) states that many sexologists view the foreskin as "a complex, erotogenic structure that plays an important role ‘in the mechanical function of the penis during sexual acts, such as penetrative intercourse and masturbation’."

Protective and immunological
Gairdner (1949) states that the foreskin protects the glans. The fold of the prepuce maintains sub-preputial wetness, which mixes with exfoliated skin to form smegma. The American Academy of Pediatrics (1999) state that "no controlled scientific data are available regarding differing immune function in a penis with or without a foreskin." Inferior hygiene has been associated with balanitis, though excessive washing can cause non-specific dermatitis.

Evolution
In primates, the foreskin is present in the genitalia of both sexes and likely has been present for millions of years of evolution. The evolution of complex penile morphologies like the foreskin may have been influenced by females. . There is also evidence that the foreskin plays an evolutionary role in the protection of the glans insofar that the foreskin begins to fully retract around puberty, when mating becomes important in human males [Fate of the Fore].

Foreskin and HIV
There has been research surrounding the effect of HIV acquisition and the presence of a foreskin. It is estimated by some that circumcision reduces the risk of HIV in men in Uganda by 50 to 60 percent [SITE FORESKIN SURFACE AREA AND HIV ACQUISITION IN UGANDA]. In addition, both the World Health Organization [| ref] and the United Nations Joint Program on HIV [|ref] have recommended circumcision for males as a means of HIV prevention UGANDA.

Male circumcision is important in the prevention of HIV in men as it removes Langerhans cells (see below) and T lymphocyte cells, which are vulnerable tissues. The removal of these cells leaves a smaller surface area for infections, therefore, leaving a smaller surface area for HIV contraction.

[SITE UGanada] did a study of HIV acquisition in Uganda and compared the size of the foreskin in men. They found that as the surface area of the foreskin increase, so did the likelihood that the individual would contract HIV. They also found that individuals who seroconverted (went from negative to positive- in this case for HIV) had larger foreskin surface areas than did individuals who remained seronegative (negative for the presence of HIV). The results from the study demonstrate that the size of the foreskin is implicated in the acquisition of HIV in males in Uganda.

[SITE India] found the same results as did the [SITE Uganda] study – circumcised men have a reduced risk of HIV when compared to men with an intact foreskin. They also found that the presence of a foreskin increased the acquisition of HIV in men, as the presence of the foreskin contains Langerhans cells and CD4+ lymphocytes, which increases the surface area to contract the disease.

[SITE Male Circumcision: Health] found that the prevalence of men with a foreskin and the acquisition of HIV is confounded with types of sexual practices and types of cleaning and hygiene behaviours.

Conditions
Simmons et al. (2007) report that the foreskin's presence "frequently predisposes to medical problems, including balanitis, phimosis, venereal disease and penile cancer", and additionally state that "because we now are able to effectively treat foreskin related maladies, some societies are shifting toward foreskin preservation."

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. Before adulthood, the foreskin may still be separating from the glans. Phimosis can be treated by gently stretching the foreskin, by changing masturbation habits, using topical steroid ointments, preputioplasty, or by the more radical option of circumcision. 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 ischaemia of the glans penis.

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.

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

Circumcision
Circumcision is the removal of the foreskin, either partially or completely. It may be done for religious requirements, health reasons such as to treat a medical disorder, or personal preferences surrounding hygiene. Circumcision may also be performed as a right of passage, a cultural marking, or for blood sacrifices [The prepuce]. In men, the majority of the foreskin is removed during circumcision; however, in women this is more varied [The prepuce]. There are other reasons given for routine circumcision, such as increased pleasure during intercourse and a circumcised penis is more aesthetically pleasing [a consider of rout]. These claims are not substantiated in research. Preputioplasty is a minor procedure designed to relieve a tight foreskin without resorting to circumcision.

The prevalence of circumcision is varied across cultures and nations. In the United States, approximately 80 percent of newborn boys are circumcised; however, the occurrence of newborn circumcision is much lower in European nations and Canada [benefits of newborn circ]. There are anticircumcision groups in the United States that claim that genital hygiene can be easily maintained and the acquisition of smegma or other infections can be eliminated by proper care; however, research has shown that hygiene for uncircumcised males is poor, considering lack of education on proper cleaning of the foreskin [benefits of newborn circ].

History of Circumcision
The presence of ritualistic circumcision has occurred for thousands of years. History reports that routine circumcisions occurred in Africa over 5000 years ago and occurred in the Middle East at least 3000 years ago. In the United States and Canada routine circumcisions began in the late 19th and early 20th century under medical influence largely to prevent masturbation. Doctors mentioned hygiene and the importance of circumcision on the health of young boys [Assessment of Health Benefits and Risks].

In the United States, the last forty years have had large fluctuations in the prevalence of routine circumcisions. As mentioned above, routine circumcision was advised for boys by the medical culture. In the 1970s it was estimated that over 80 percent of newborn males were circumcised. However in 1971 this changed when the American Academy of Paediatrics stated that there was insufficient health evidence to support routine circumcisions. They began to argue against the common routine neonatal circumcisions that were occurring in the United States. By the early 1980s routine circumcision in the United States had dropped to approximately 60 percent, but in 1989 that changed again. The American Academy of Paediatrics changed its position on routine circumcision again, this time neither denying nor supporting routine circumcision. In 1990 the circumcision rate in the United States increased to over 80 percent [Assessment of Health benefits].

Complications Surrounding Circumcision
There are many complications that can result from routine surgery, in this case, circumcision. These complications range from immediate complications right after the circumcision occurs, to more long-term complications.

Some immediate complications include: [A consideration of routine neonatal circ—all in this section]
 * Haemorrhage
 * Infection
 * Ulceration
 * Supparation
 * Local infections may lead to more serious complications
 * Surgical Trauma
 * Denuded penile shaft (loss of penile skin)
 * Accidental lacerations
 * Incomplete circumcision
 * Secondary penile deformity
 * Accidental amputation of the glans

Some delayed complications include:
 * Prolonged and frequent contact with feces or ammoniacal urine
 * Meatal stenosis
 * Psychogenic concerns

Foreskin Restoration
Foreskin restoration techniques (developed to help circumcised men 'regrow' a skin covering for the glans by tissue expansion) can be used by men with short foreskins to lengthen the natural foreskin so that it covers the glans. A narrow foreskin may also be widened by tissue expansion.

Genital Peircings
Other practices include genital piercings involving the foreskin and slitting the foreskin.

Langerhans cells
Langerhans cells are immature dendritic cells that are found in all areas of the penile epithelium, but are most superficial in the inner surface of the foreskin. A study by Szabo and Short (2000) 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." 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. However, de Witte et al. (2007) argued that langerin, produced by Langerhans cells, blocks the transmission of HIV to T cells.

Foreskin-based medical and consumer products
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.

Human growth factors derived from newborns' foreskins are used to make a commercial anti-wrinkle skin cream, TNS Recovery Complex.

Foreskins of babies are also used for skin graft tissue,  and for β-interferon-based drugs.

Foreskin fibroblasts have been used in biomedical research.

Foreskin in non-human species
In koalas, the foreskin contains naturally occurring bacteria that play an important role in fertilization. Almost all mammal penises have foreskins, although in 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.

During musth, a male elephant may urinate with the penis still in the sheath, which causes the urine to spray on the hind legs.

Male dogs have a conspicuous penis sheath.