In male human anatomy, 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. 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. The highly innervated mucocutaneous zone of the penis occurs near the tip of the foreskin. The foreskin is mobile, fairly stretchable, and acts as a natural lubricant.
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.
The World Health Organization debates the precise functions of the foreskin, which may include "keeping the glans moist, protecting the developing penis in utero, or enhancing sexual pleasure due to the presence of nerve receptors".
The foreskin may become subject to a number of pathological conditions. Most conditions are rare, and easily treated. In some cases, particularly with chronic conditions, treatment may include circumcision, a procedure where the foreskin is partially or completely removed.
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. The ridged band of highly innervated tissue is located just inside the tip of the foreskin. 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. 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.
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. Template Template-Fact" style="white-space:nowrap;">[medical citation needed]
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."
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. Template Template-Fact" style="white-space:nowrap;">[medical citation needed]
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. When the foreskin is longer than the erect penis, it will not spontaneously retract upon erection.
It is shown that manual foreskin retraction during childhood or even adulthood serves as a stimulant to normal development and automatic retraction of the foreskin, which suggests that many conditions affecting the foreskin may be prevented or cured behaviorally. Template Template-Fact" style="white-space:nowrap;">[medical citation needed] 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. 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.
The World Health Organization (2007) states 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 helps to provide sufficient skin during an erection.
The foreskin protects the glans. 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. The fold of the prepuce maintains sub-preputial wetness, which mixes with exfoliated skin to form smegma. Template Template-Fact" style="white-space:nowrap;">
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 diseases in adults.
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."
The foreskin is specialised tissue that is packed with nerves and contains stretch receptors.
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'."
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.
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. 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.
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.
Some birth defects of the foreskin can occur; all of them are rare. In aposthia there is no foreskin at birth,:37-39 in micropathia the foreskin doesn't cover the glans,:41-45 and in macroposthia, also called and congenital megaprepuce, the foreskin extends well past the end of the glans.:47–50
Preputioplasty is the most common foreskin reconstuction technique, most often done when a boy is born with a foreskin that is too small;:177 a similar procedure is performed to relieve a tight foreskin without resorting to circumcision.: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.:257 Circumcision may also be performed on children or adults to treat phimosis, balanitis, or to prevent transmission of sexually transmitted disease.:166 As of 2012 no successful technique to reconstruct a circumcised foreskin had been published.: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.
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.
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