Foreskin
Double-layered fold covering the glans of the human penis.
The foreskin, also called the prepuce, is a double-layered fold of skin, mucosa, and muscle at the tip of the penis. It covers the glans and urinary opening, is mobile and stretchable, and keeps the glans moist. All primates and most mammals have a similar structure, the penile sheath.
Quick Facts
- Latin
- praeputium, preputium penis
- Precursor
- Genital tubercle, urogenital folds
- System
- Male reproductive system
- Artery
- Dorsal artery of the penis
- Vein
- Dorsal veins of the penis
- Nerve
- Dorsal nerve of the penis
Facts from the source article.
Structure
The outer foreskin is a continuation of the penile shaft skin, covered by keratinized stratified squamous epithelium. The inner foreskin is a continuation of the glans epithelium, composed of glabrous squamous mucous membrane similar to the inside of the eyelid or mouth, and has a great capacity for self-repair. The outer foreskin measures 7–100 cm², and the inner foreskin measures 18–68 cm². The mucocutaneous zone is where the outer and inner foreskin meet.
The inner foreskin attaches to the glans via the frenulum, a highly vascularized tissue; the World Health Organization notes that the frenulum forms the interface between the outer and inner foreskin layers and tightens to narrow the foreskin opening when the penis is not erect. The foreskin is a laminar structure of outer skin, mucosal epithelium, lamina propria, dartos fascia, and dermis. The superficial dartos fascia, formerly called the peripenic muscle, extends within the prepuce and contains abundant elastic fibers that form a whorl at the tip, the preputial orifice, narrow during infancy and childhood.
This fascia is sensitive to temperature, expanding and contracting, and is loosely connected to underlying tissue, providing mobility and elasticity. Langerhans cells, immature dendritic cells, are found in all penile epithelium but are most superficial on the inner foreskin surface.
Development
The penis develops from the genital tubercle, an initially undifferentiated phallic structure that forms in the early weeks of pregnancy. Differentiation into a penis occurs under male hormones from the testicles, becoming evident between twelve and sixteen weeks of gestation. Preputial development begins around eleven weeks or earlier and continues up to eighteen weeks. Historically, two main theories describe preputial development: one proposes formation from dorsal skin with progressive distal extension to cover and fuse with the glans epithelium; another suggests the preputial fold results from ingrowth of the cellular lamina that rolls outward over the glans, with the lamina also expanding backward to form an ingrowing fold at the coronal sulcus.
By eleven to twelve weeks, a thickening of the epidermis forms the preputial fold, with the preputial lamina on its underside expanding dorsolaterally over the glans base. At thirteen weeks, the prepuce covers only part of the glans. By sixteen weeks, bilateral preputial folds cover most of the glans, and the ventral sides fuse in the midline; the penile raphe, a continuation of the perineal raphe, appears on the ventral penis from fusion of urethral and preputial folds.
The dorsal nerve of the penis, present from nine weeks, fully expands to the distal glans and prepuce by sixteen weeks. Foreskin development is complete at nineteen weeks. By the end of the second trimester, the glans and prepuce are fused by the balanopreputial lamina. At birth, this membrane is physiologically adherent, preventing retraction in infancy and early childhood; non-retractile foreskin naturally resolves at varying ages in childhood, preadolescence, or puberty.
Clinical significance
The foreskin can be involved in balanitis, phimosis, sexually transmitted infections, and penile cancer. The American Academy of Pediatricians' 2012 technical report on circumcision noted that the foreskin can harbor microorganisms that may increase urinary tract infection risk in some infants and contribute to transmission of some sexually transmitted infections in adults. Excessive soap washing may irritate the mucosa, so gentle washing is recommended.
Frenulum breve is a frenulum too short to allow full retraction, causing discomfort during intercourse. Phimosis, where an adult foreskin cannot be retracted properly, may be treated with topical steroid ointments and lubricants; severe cases may require circumcision. Posthitis is inflammation of the foreskin. Paraphimosis occurs when a tight foreskin becomes trapped behind the glans and swells, potentially cutting off blood supply and causing glans ischemia.
Lichen sclerosus, a chronic inflammatory skin condition most common in adult women but also seen in men and children, can be treated effectively with topical clobetasol propionate and mometasone furoate. Rare birth defects include aposthia (no foreskin at birth), micropathia (foreskin does not cover the glans), and macroposthia (foreskin extends well past the glans). Larger foreskins place uncircumcised men at increased risk of HIV infection, likely due to larger inner foreskin surface area and high concentration of Langerhans cells.
Society and culture
Circumcision, the partial or complete removal of the foreskin, is performed electively for prophylactic, cultural, or religious reasons, or to treat phimosis, balanitis, and other pathologies; its ethics in children is controversial. Some men use weights or devices to stretch penile skin to regrow a foreskin, though the resulting tissue does not fully replicate original features. Other practices include genital piercings involving the foreskin and slitting the foreskin.
Preputioplasty is the most common foreskin reconstruction technique, often done when a boy is born with a foreskin too small, or to relieve a tight foreskin without circumcision. Foreskins from circumcision are used by researchers to study human skin structure and proteins; newborn foreskins are useful in manufacturing more human skin. Baby foreskins are also used for skin grafts and β-interferon-based drugs. Foreskin-derived fibroblasts have applications in biomedical research and cosmetics.
In the Greco-Roman world, the foreskin was considered a sign of beauty, civility, and masculinity; some Jews in that era undertook epispasm to restore their foreskins to avoid ostracization, as baring the glans was considered vulgar. In ancient Greece, longer foreskins were valued. The earliest known illustrative depiction of the foreskin dates back to Egyptian kingdoms, and it has been depicted in art from different historical ages.
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