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The penis is the external male organ of urination and copulation.[1] The penis is also known as the phallus.

The body of the penis consists of three cylindrical-shaped masses of erectile tissue which run the length of the penis. Two of the masses lie alongside each other and end behind the head of the penis. The third mass lies underneath them. This latter mass contains the urethra. The penis terminates in an oval or cone-shaped body, the glans penis, which contains the exterior opening of the urethra, or meatus.[1]

The normal intact, foreskinned penis is enveloped in a tube of loose, highly innervated, movable, erogenous skin,[2] the foreskin or prepuce, which enables it to expand freely during erection.[3] The skin ends just behind the glans penis but folds forward to cover it, this forming the preputial sac and, if long enough, the acroposthion. The moist preputial sac may harmlessly collect oil-bearing smegma, which is helpful in preventing dermatitis.[4]

The skin of the adult penis normally is somewhat darker than the rest of the body. This condition is called hyperpigmentation.


The penis — the organ of copulation — is heavily innervated with afferent[5] nerves — meaning that sensation, which is needed for male sexual function, is transmitted to the spinal cord and/or central nervous system. The penis is also innervated by the sympathetic autonomic nervous system (SAMS) and parasympathetic autonomic nervous system (PAMS).[6] The penis is innervated by both dorsal and perineal nerves.[6]

The innervation in the tube of foreskin translates movement and stretching into pleasurable sensation.[7] [8]


  • Root of the penis (radix): It is the attached part, consisting of the bulb of penis in the middle and the crus of penis, one on either side of the bulb. It lies within the superficial perineal pouch.
  • Body of the penis (corpus): It has two surfaces: dorsal (posterosuperior in the erect penis), and ventral or urethral (facing downwards and backwards in the flaccid penis). The ventral surface is marked by a groove in a lateral direction.
  • Epithelium of the penis consists of the shaft skin, the foreskin, and the preputial mucosa on the inside of the foreskin and covering the glans penis. The epithelium is not attached to the underlying shaft so it is free to glide to and fro.[9]

The following content is part of the Circumpendium.

Anatomy and development of the male genital organ

Up to the ninth week of pregnancy, both male and female genital organs develop identically. Genital tubercle, labioscrotal swelling, genital fold and urogenital membrane have developed.

Only after that do the different external features emerge in the fetus. Between the 11th and 17th week the genital tubercle becomes the clitoris in females, and the glans in males.

In girls, the genital fold remains open, in boys it grows together. It transforms into the inner labia and the clitoral hood in girls, and into the foreskin in boys. The labioscrotal swelling becomes the outer labia and scrotum respectively.

The growing together of the folds results in the seam that runs from the underside of the scrotum and the penile shaft up to the tip of the foreskin. The penis now consists of the shaft containing the erectile tissue, with the glans at the top. The shaft is surrounded by the shaft skin which, however, is not knitted to it. This mobility, combined with the stretching capabilities of the skin, allows for the growth in dimension of the penis during an erection. During an erection the erectile tissue fills with blood, giving the penis its stiffness and enlarged size.

In the area of the glans the shaft skin transitions into the outer layer of the foreskin, which extends past the tip of the glans. Parallel to that runs the inner layer of the foreskin. It is attached behind the rim of the glans, and runs between the glans and the outer foreskin layer, also past the tip of the glans. At the tip, the inner and outer foreskin layers are joined together.

This junction makes up the ridged band. At the underside of the penis, in the area of the seam, the inner foreskin layer is connected to the glans by the frenulum.


Like the shaft skin, the foreskin layers are neither fused to the penis, nor to each other, but are moveable against each other. This enables the foreskin to be retracted all the way past the glans until it is stopped by the frenulum.


At the time of birth, the development of the external male genital organs is not completely finished. At this stage, the foreskin and glans share an epithelium (mucous layer, the balano-preputial membrane) that fuses the two together. It serves to protect the glans during infancy, and dissolves as the child develops. Premature forcible retraction of the foreskin will tear this membrane, causing great pain and injury to the boy, who suffers this abuse. The child, himself, should be the first person to retract his foreskin.[10] [11]

Only then the foreskin can be retracted. The age at which this occurs is subject to the child's individual development. If the foreskin is retracted prematurely, before it has fully separated, that can result in painful tears and infections.

The widening of the foreskin also depends on age. A child's foreskin may be too tight to be retracted all the way past the glans, even though it has already completely separated from the glans. This early foreskin tightness, frequently confused with (phimosis), is a normal stage of development and vanishes with increasing age in most boys.

A study by the Danish paediatrician and school doctor, Jakob Øster, of 9,545 examinations of pupils, published in 1968, led to the following results[12]:

Age Phimosis Tightness Incomplete separation Not retractable Fully retractable
6 to 7 8% 1% 63% 77% 23%
8 to 9 6% 2% 58% 66% 34%
10 to 11 6% 2% 48% 56% 44%
12 to 13 3% 3% 34% 40% 60%
14 to 15 1% 1% 13% 15% 85%
16 to 17 1% 1% 3% 5% 95%

Classification according to Øster:

phimosis: Foreskin tightness prohibiting retraction

Tightness: Foreskin tightness hampering retraction

Thorvaldsen & Meyhoff (2005) conducted a survey of 4000 young men in Denmark. They report that the mean age of first foreskin retraction is 10.4 years in Denmark.[13] Non-retractile foreskin is the more common condition until about 10-11 years of age.

Penis size

The average length of the adult penis is 5.5 inches or 14 centimeters. The average girth is 4.6 inches or 11.7 centimeters.[14]


What Happens to Your Penis As You Age? A Doctor Explains

See also

External links


  1. a b REFweb (2003). penis, The Free Dictionary by Farlex.. Retrieved 23 May 2022.
  2. REFjournal Winkelmann RK. The erogenous zones: their nerve supply and significance. Mayo Clin Proc. 21 January 1959; 34(3): 39-47. PMID. Retrieved 4 June 2021.
  3. REFjournal Earp BD, Steinfeld R. Genital autonomy and sexual well-being. Current Sexual Health Reports. 2018; 10(1): 7-17. DOI. Retrieved 2 January 2024.
  4. REFjournal Birley HDL, Walker MM, Luzzi GA, Bell R, et al. Clinical Features and management of recurrent balanitis; association with atopy and genital washing] PDF. Genitourin Med. October 1993; 69(5): 400-3. PMID. PMC. DOI. Retrieved 29 November 2023.
  5. REFweb Anonymous (2003). Afferent, The Free Dictionary by Farlex. Retrieved 24 November 2023.
  6. a b REFjournal Cepeda-Emiliani A, Gándara-Cortés M, Otero-Alén M, García H, Suárez-Quintanilla J, García-Caballero T, Gallego R, García-Caballero R. Immunohistological study of the density and distribution of human penile neural tissue: gradient hypothesis. Int J Impot Res. 2 May 2023; 35(3): 286-305. PMID. DOI. Retrieved 24 November 2023.
  7. REFjournal García-Mesa, Yolanda, García-Piqueras, Jorge, Cobo, Ramón, Martín-Cruces, José, Suazo, Iván, García-Suárez, Olivia, Feito, Jorge. Sensory innervation of the human male prepuce: Meissner's corpuscles predominate. Journal of Anatomy. October 2021; 239(4): 892-902. PMID. PMC. DOI. Retrieved 26 November 2023.
  8. REFweb Anonymous (17 February 2024). What Do The Eyelids, Lips, Fingertips & The Intact Penis Have in Common?, Intact America. Retrieved 18 February 2024.
  9. REFweb Young, Hugh. How the foreskin works, Circumstitions. Retrieved 2 October 2019.
  10. REFjournal Wright JE. Further to the Further Fate of the Foreskin. Med J Aust. 1994; 160: 134-5. PMID. Retrieved 1 October 2019.
    Quote: The normal prepuce should be left alone, with no attempt to retract it until the boy is able to do it himself, at the earliest at three years of age.
  11. REFdocument Answers to Your Questions About Premature (Forcible) Retraction of Your Son's Foreskin PDF, NOCIRC (San Anselmo). (2000).
  12. REFjournal Øster J. Further Date of the Foreskin: Incidence of Preputial Adhesions, Phimosis, and Smegma among Danish Schoolboys. Arch Dis Child. 1968; 43(228): 200-3. PMID. PMC. DOI. Retrieved 30 December 2020.
  13. REFjournal Thorvaldsen MA, Meyhoff H. Patologisk eller fysiologisk fimose?. Ugeskr Læger. 2005; 167(17): 1858-1862. PMID. Retrieved 1 October 2019.
  14. REFweb Unravelling size, Retrieved 29 December 2023.