The human penis is an external male
intromittent organ
An intromittent organ is any external organ of a male organism that is specialized to deliver sperm during copulation. Intromittent organs are found most often in terrestrial species, as most non-mammalian aquatic species fertilize their eggs e ...
that additionally serves as the
urinary duct. The main parts are the root (radix); the body (corpus); and the
epithelium
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
of the
penis
A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males do n ...
including the shaft skin and the
foreskin
In male human anatomy, the foreskin, also known as the prepuce, is the double-layered fold of skin, mucosal and muscular tissue at the distal end of the human penis that covers the glans and the urinary meatus. The foreskin is attached to the g ...
(prepuce) covering the
glans penis
In male human anatomy, the glans penis, commonly referred to as the glans, is the bulbous structure at the distal end of the human penis that is the human male's most sensitive erogenous zone and their primary anatomical source of sexual p ...
. The body of the penis is made up of three columns of
tissue: two
corpora cavernosa on the
dorsal side
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
and
corpus spongiosum
The corpus spongiosum is the mass of spongy tissue surrounding the male urethra within the penis. It is also called the corpus cavernosum urethrae in older texts.
Anatomy
The proximal part of the corpus spongiosum is expanded to form the uret ...
between them on the
ventral side
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
. The human male
urethra
The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra con ...
passes through the
prostate gland
The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, chemically, and physio ...
, where it is joined by the
ejaculatory duct
The ejaculatory ducts (''ductus ejaculatorii'') are paired structures in male anatomy. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the ureth ...
, and then through the penis. The urethra traverses the corpus spongiosum, and its opening, the
meatus
In anatomy, a meatus (, ),''OED'' 2nd edition, 1989, as . plural "meatus" or "meatuses", (), lies on the tip of the glans penis. It is a passage both for
urination
Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...
and
ejaculation
Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential componen ...
of
semen
Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Semen i ...
(''see''
male reproductive system
The male reproductive system consists of a number of sex organs that play a role in the process of human reproduction. These organs are located on the outside of the body and within the pelvis.
The main male sex organs are the penis and the tes ...
.)
Most of the penis
develops from the same embryonic tissue as the
clitoris
The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), above the ope ...
in females. The skin around the penis and the urethra share the same embryonic origin as the
labia minora
The labia minora (Latin for 'smaller lips', singular: ''labium minus'', 'smaller lip'), also known as the inner labia, inner lips, vaginal lips or nymphae are two flaps of skin on either side of the human vaginal opening in the vulva, situated be ...
in females.
An erection
An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged. Penile erection is the result of a complex interaction of psychological, neural, vascular, ...
is the stiffening expansion and orthogonal reorientation of the penis, which occurs during sexual arousal. Erections can occur in non-sexual situations; spontaneous non-sexual erections frequently occur during adolescence and sleep. In its flaccid state the penis is smaller, gives to pressure, and the glans is covered by the foreskin. In its fully erect state the corpus becomes rigid and the glans becomes engorged but not rigid. An erect penis may be straight or curved and may point at an upward angle, a downward angle, or straight ahead. , the average erect human penis is 13.12 cm (5.17 inches) long and has a circumference of 11.66 cm (4.59 inches). Neither age nor size of the flaccid penis accurately predicts erectile length.
There are several common body modifications to the penis, including circumcision
Circumcision is a surgical procedure, procedure that removes the foreskin from the human penis. In the most common form of the operation, the foreskin is extended with forceps, then a circumcision device may be placed, after which the foreskin ...
and piercings
Body piercing, which is a form of body modification, is the practice of puncturing or cutting a part of the human body, creating an opening in which jewelry may be worn, or where an Implant (medicine), implant could be inserted. The word ''pier ...
.
Anatomy
Parts
* Root of the penis (radix): It is the attached part, consisting of the bulb of penis
Just before each crus of the penis meets its fellow, it presents a slight enlargement, which Georg Ludwig Kobelt named the bulb of the corpus cavernosum penis. The bulb of penis is also known as the urethral bulb.
The bulb is homologous to the v ...
in the middle and the crus of penis
For their anterior three-fourths the corpora cavernosa penis lie in intimate apposition with one another, but behind they diverge in the form of two tapering processes, known as the crura, which are firmly connected to the ischial rami.
Traced f ...
, one on either side of the bulb. It lies within the superficial perineal pouch. The crus of penis is attached to the pubic arch.
* Body of the penis (corpus): The pendulous part of the penis. 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 the penile raphe. The base of the body of penis is supported by the suspensory ligament A suspensory ligament is a ligament that supports a body part, especially an organ.
Types include:
* Suspensory ligament of axilla, also known as Gerdy's ligament
* Cooper's ligaments, also known as the suspensory ligaments of Cooper or Suspensory ...
which is attached to the pubic symphysis
The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubic ...
.
* Epithelium
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
of the penis consists of the shaft skin
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
, the foreskin
In male human anatomy, the foreskin, also known as the prepuce, is the double-layered fold of skin, mucosal and muscular tissue at the distal end of the human penis that covers the glans and the urinary meatus. The foreskin is attached to the g ...
, and the preputial mucosa
The preputial mucosa of the penis is the epithelium of the inside of the prepuce, or foreskin. To differentiate it from the cutaneous skin of the outside of the prepuce, it is sometimes referred to as the inner mucosa. It starts at the ridged band ...
on the inside of the foreskin and covering the glans penis
In male human anatomy, the glans penis, commonly referred to as the glans, is the bulbous structure at the distal end of the human penis that is the human male's most sensitive erogenous zone and their primary anatomical source of sexual p ...
. The epithelium is not attached to the underlying shaft so it is free to glide to and fro.
Structure
The human penis is made up of three columns of tissue: two corpora cavernosa lie next to each other on the dorsal side
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
and one corpus spongiosum
The corpus spongiosum is the mass of spongy tissue surrounding the male urethra within the penis. It is also called the corpus cavernosum urethrae in older texts.
Anatomy
The proximal part of the corpus spongiosum is expanded to form the uret ...
lies between them on the ventral side
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
.
The corpus cavernosum forms most of the penis and contains blood vessels that fill with blood to help make an erection.
The crus of penis is the proximal parts of the corpora cavernosum. The corpus spongiosum is an erectile tissue surrounding the urethra. The proximal parts of the corpus spongiosum form the bulb of penis and the distal ends form the glans penis.
The enlarged and bulbous-shaped end of the corpus spongiosum forms the glans penis with two specific types of sinusoids, which supports the foreskin, or prepuce, a loose fold of skin that in adults can retract to expose the glans. The area on the underside of the penis, where the foreskin is attached, is called the frenum
A frenulum (or frenum, plural: frenula or frena, from the Latin ''frēnulum'', "little bridle", the diminutive of ''frēnum'') is a small fold of tissue that secures the motion of a mobile organ in the body.
In human anatomy
Frenula on the hu ...
, or frenulum. The rounded base of the glans is called the corona
Corona (from the Latin for 'crown') most commonly refers to:
* Stellar corona, the outer atmosphere of the Sun or another star
* Corona (beer), a Mexican beer
* Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...
. The perineal raphe
The perineal raphe is a visible line or ridge of tissue on the body that extends from the anus through the perineum to scrotum (male) or labia majora (female). It is found in both males and females, arises from the fusion of the urogenital folds, ...
is the noticeable line along the underside of the penis.
The urethra
The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra con ...
, which is the last part of the urinary tract
The urinary system, also known as the urinary tract or renal system, consists of the kidneys, ureters, bladder, and the urethra. The purpose of the urinary system is to eliminate waste from the body, regulate blood volume and blood pressure, con ...
, traverses the corpus spongiosum, and its opening, known as the meatus
In anatomy, a meatus (, ),''OED'' 2nd edition, 1989, as . plural "meatus" or "meatuses", , lies on the tip of the glans penis. It is a passage both for urine and for the ejaculation of semen. Sperm
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...
are produced in the testes
A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoster ...
and stored in the attached epididymis
The epididymis (; plural: epididymides or ) is a tube that connects a testicle to a vas deferens in the male reproductive system. It is a single, narrow, tightly-coiled tube in adult humans, in length. It serves as an interconnection between the ...
. During ejaculation, sperm are propelled up the vas deferens
The vas deferens or ductus deferens is part of the male reproductive system of many vertebrates. The ducts transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled tube ...
, two ducts that pass over and behind the bladder. Fluids are added by the seminal vesicles
The seminal vesicles (also called vesicular glands, or seminal glands) are a pair of two convoluted tubular glands that lie behind the urinary bladder of some male mammals. They secrete fluid that partly composes the semen.
The vesicles are 5 ...
and the vas deferens turns into the ejaculatory duct
The ejaculatory ducts (''ductus ejaculatorii'') are paired structures in male anatomy. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the ureth ...
s, which join the urethra inside the prostate
The prostate is both an Male accessory gland, accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, ...
gland. The prostate as well as the bulbourethral gland
The bulbourethral glands or Cowper's glands (named for English anatomist William Cowper) are two small exocrine glands in the reproductive system of many male mammals (of all domesticated animals, they are absent only in dogs). They are homolog ...
s add further secretions, and the semen is expelled through the penis.
The raphe
Raphe (; from Greek ῥαφή, "seam"Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with the assistance of. Roderick McKenzie.'' Oxford: Clarendon Press.) has several diffe ...
is the visible ridge between the lateral
Lateral is a geometric term of location which may refer to:
Healthcare
*Lateral (anatomy), an anatomical direction
*Lateral cricoarytenoid muscle
*Lateral release (surgery), a surgical procedure on the side of a kneecap
Phonetics
*Lateral cons ...
halves of the penis, found on the ventral or underside of the penis, running from the meatus (opening of the urethra) across the scrotum
The scrotum or scrotal sac is an anatomical male reproductive structure located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum cont ...
to the perineum
The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), includi ...
(area between scrotum and anus
The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, d ...
).
The human penis differs from those of most other mammals, as it has no baculum
The baculum (also penis bone, penile bone, or ''os penis'', ''os genitale'' or ''os priapi'') is a bone found in the penis of many placental mammals. It is absent from the human penis, but present in the penises of some primates, such as the ...
(or erectile bone) and instead relies entirely on engorgement with blood to reach its erect state. A distal ligament buttresses the glans penis and plays an integral role to the penile fibroskeleton, and the structure is called "os analog," a term coined by Geng Long Hsu
Geng Long Hsu () is a Taiwanese urologic surgeon and former clinical professor at China Medical University. He earned his MD from National Taiwan University in 1985 and completed his research fellowship from the University of California San F ...
in the Encyclopedia of Reproduction. It is a remnant of baculum
The baculum (also penis bone, penile bone, or ''os penis'', ''os genitale'' or ''os priapi'') is a bone found in the penis of many placental mammals. It is absent from the human penis, but present in the penises of some primates, such as the ...
evolved likely due to change in mating practice.
The human penis cannot be withdrawn into the groin, and it is larger than average in the animal kingdom in proportion to body mass. The human penis is reciprocating from a cotton soft to a bony rigidity resulting from penile arterial flow varied between 2–3 to 60-80 mL/Min implies the most ideal milieu to apply Pascal's law in the entire human body; the overall structure is unique.
Size
Penile measurements vary, with studies that rely on self-measurement reporting a significantly higher average size than those which rely on measurements taken by health professional. A 2015 systematic review of 15,521 men in which the subjects were measured by health professionals concluded that the average length of an erect human penis is 13.12 cm (5.17 inches) long, while the average circumference of an erect human penis is 11.66 cm (4.59 inches).[
Among all primates, the human penis is the largest in girth, but is comparable to the ]chimpanzee
The chimpanzee (''Pan troglodytes''), also known as simply the chimp, is a species of great ape native to the forest and savannah of tropical Africa. It has four confirmed subspecies and a fifth proposed subspecies. When its close relative th ...
penis and the penises of certain other primates in length. Penis size is affected by genetics
Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...
, but also by environmental factors such as fertility medication
Fertility medications, also known as fertility drugs, are medications which enhance reproductive fertility. For women, fertility medication is used to stimulate follicle development of the ovary. There are very few fertility medication options a ...
s and chemical/pollution exposure. The longest officially documented human penis was found by physician Robert Latou Dickinson
Robert Latou Dickinson (1861–1950) was an American obstetrician and gynecologist, surgeon, maternal health educator, artist, sculptor and medical illustrator, and research scientist.
Early life
Robert Latou Dickinson was born on February 21, 1 ...
. It was long and in circumference.
Normal variations
* ''Pearly penile papules'' are raised bumps of somewhat paler color around the base (sulcus) of the glans which typically develop in men aged 20 to 40. As of 1999, different studies had produced estimates of incidence ranging from 8 to 48 percent of all men. They may be mistaken for warts, but are not harmful or infectious and do not require treatment.
*Fordyce's spot
Fordyce spots (also termed Fordyce granules)James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology''. (10th ed.). Saunders. . are visible sebaceous glands that are present in most individuals ...
s are small, raised, yellowish-white spots 1–2 mm in diameter that may appear on the penis, which again are common and not infectious.
*''Sebaceous prominences'' are raised bumps similar to Fordyce's spots on the shaft of the penis, located at the sebaceous gland
A sebaceous gland is a microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur in the greatest number ...
s and are normal.
*Phimosis
Phimosis (from Greek language, Greek φίμωσις ''phimōsis'' 'muzzling'.) is a condition in which the foreskin of the Human penis, penis cannot stretch to allow it to be pulled back past the Glans penis, glans. A balloon-like swelling under ...
is an inability to retract the foreskin fully. It is normal and harmless in infancy and pre-pubescence, occurring in about 8% of boys at age 10. According to the British Medical Association, treatment (topical steroid cream and/or manual stretching) does not need to be considered until age 19.
*Curvature: few penises are completely straight, with curves commonly seen in all directions (up, down, left, right). Sometimes the curve is very prominent but it rarely inhibits sexual intercourse
Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetrat ...
. Curvature as great as 30° is considered normal and medical treatment is rarely considered unless the angle exceeds 45°. Changes to the curvature of a penis may be caused by Peyronie's disease
Peyronie's disease is a connective tissue disorder involving the growth of fibrous plaques in the soft tissue of the penis. Specifically, scar tissue forms in the tunica albuginea, the thick sheath of tissue surrounding the corpora cavernosa, ca ...
.
Development
Differences between female and male organs
In the developing fetus, the genital tubercle
A genital tubercle or phallic tubercle is a body of tissue present in the development of the reproductive system. It forms in the ventral, caudal region of mammalian embryos of both sexes, and eventually develops into a primordial phallus. In the ...
develops into the glans of the penis in males and into the clitoral glans
The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), above the ope ...
in females; they are homologous. The urogenital fold
The development of the reproductive system is the part of embryonic growth that results in the sex organs and contributes to sexual differentiation. Due to its large overlap with development of the urinary system, the two systems are typically ...
develops into the skin around the shaft of the penis and the urethra in males and into the labia minora
The labia minora (Latin for 'smaller lips', singular: ''labium minus'', 'smaller lip'), also known as the inner labia, inner lips, vaginal lips or nymphae are two flaps of skin on either side of the human vaginal opening in the vulva, situated be ...
in females.[Keith L. Moore, T. V. N. Persaud, Mark G. Torchia, The Developing Human: Clinically Oriented Embryology 10th Ed. Elsevier Health Sciences, 2015 ]
pp 267-69
/ref> The corpora cavernosa are homologous to the body of the clitoris; the corpus spongiosum is homologous to the vestibular bulbs
In female anatomy, the vestibular bulbs, bulbs of the vestibule or clitoral bulbs are two elongated masses of erectile tissue typically described as being situated on either side of the vaginal opening. They are united to each other in front by a ...
beneath the labia minora; the scrotum, homologous to the labia majora
The labia majora (singular: ''labium majus'') are two prominent longitudinal cutaneous folds that extend downward and backward from the mons pubis to the perineum. Together with the labia minora they form the labia of the vulva.
The labia majo ...
; and the foreskin, homologous to the clitoral hood
In the female human body, the clitoral hood (also called preputium clitoridis and clitoral prepuce) is a fold of skin that surrounds and protects the clitoral glans, glans of the clitoris; it also covers the external shaft of the clitoris, develop ...
. The raphe does not exist in females, because there, the two halves are not connected.
Growth in puberty
On entering puberty
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a boy. ...
, the penis, scrotum and testicles
A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testostero ...
will enlarge toward maturity. During the process, pubic hair
Pubic hair is terminal body hair that is found in the genital area of adolescent and adult humans. The hair is located on and around the sex organs and sometimes at the top of the inside of the thighs. In the pubic region around the pubis bon ...
grows above and around the penis. A large-scale study assessing penis size in thousands of 17- to 19-year-old males found no difference in average penis size between 17-year-olds and 19-year-olds. From this, it can be concluded that penile growth is typically complete not later than age 17, and possibly earlier.
Physiological functions
Urination
In males the expulsion of urine from the body is done through the penis. The urethra drains the bladder through the prostate gland
The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, chemically, and physio ...
where it is joined by the ejaculatory duct
The ejaculatory ducts (''ductus ejaculatorii'') are paired structures in male anatomy. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the ureth ...
, and then onward to the penis. At the root of the penis (the proximal end of the corpus spongiosum) lies the external sphincter muscle. This is a small sphincter of striated muscle tissue
Striations means a series of ridges, furrows or linear marks, and is used in several ways:
* Glacial striation
* Striation (fatigue), in material
* Striation (geology), a ''striation'' as a result of a geological fault
* Striation Valley, in Anta ...
and is in healthy males under voluntary control. Relaxing the urethra sphincter allows the urine in the upper urethra to enter the penis properly and thus empty the urinary bladder.
Physiologically, urination involves coordination between the central
Central is an adjective usually referring to being in the center of some place or (mathematical) object.
Central may also refer to:
Directions and generalised locations
* Central Africa, a region in the centre of Africa continent, also known as ...
, autonomic, and somatic nervous system
The somatic nervous system (SNS), or voluntary nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles.
The somatic nervous system consists of sensory nerves carryi ...
s. In infants, some elderly individuals, and those with neurological injury, urination may occur as an involuntary reflex. Brain centers that regulate urination include the pontine micturition center
The Pontine micturition center (PMC, also known as Barrington's nucleus) is a collection of neuronal cell bodies located in the rostral pons in the brainstem involved in the supraspinal regulation of micturition. When activated, the PMC relaxes th ...
, periaqueductal gray
The periaqueductal gray (PAG, also known as the central gray) is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. PAG is also the primary control center for d ...
, and the cerebral cortex
The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of ...
. During erection, these centers block the relaxation of the sphincter muscles, so as to act as a physiological separation of the excretory and reproductive function of the penis, and preventing urine from entering the upper portion of the urethra during ejaculation.
Voiding position
The distal section of the urethra allows a human male to direct the stream of urine by holding the penis. This flexibility allows the male to choose the posture in which to urinate. In cultures where more than a minimum of clothing is worn, the penis allows the male to urinate while standing without removing much of the clothing. It is customary for some boys and men to urinate in seated or crouched positions. The preferred position may be influenced by cultural or religious beliefs. Research on the medical superiority of either position exists, but the data are heterogenic. A meta-analysis
A meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Meta-analyses can be performed when there are multiple scientific studies addressing the same question, with each individual study reporting me ...
summarizing the evidence found no superior position for young, healthy males. For elderly males with LUTS, however, the sitting position when compared to the standing position is differentiated by the following:
* the post void residual volume (PVR, ml) was significantly decreased
* the maximum urinary flow (Qmax, ml/s) was increased
* the voiding time (VT, s) was decreased
This urodynamic
Urodynamic testing or urodynamics is a study that assesses how the bladder and urethra are performing their job of storing and releasing urine. Urodynamic tests can help explain symptoms such as:
* incontinence
* frequent urination
* sudden, s ...
profile is related to a lower risk of urologic complications, such as cystitis
A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidney ...
and bladder stones
A bladder stone is a stone found in the urinary bladder.
Signs and symptoms
Bladder stones are small mineral deposits that can form in the bladder. In most cases bladder stones develop when the urine becomes very concentrated or when one is d ...
.
Erection
An erection is the stiffening and rising of the penis, which occurs during sexual arousal, though it can also happen in non-sexual situations. Spontaneous erections frequently occur during adolescence due to friction with clothing, a full bladder or large intestine, hormone fluctuations, nervousness, and undressing in a nonsexual situation. It is also normal for erections to occur during sleep and upon waking. (See nocturnal penile tumescence
Nocturnal penile tumescence is a spontaneous erection of the penis during sleep or when waking up. Along with nocturnal clitoral tumescence, it is also known as sleep-related erection, morning glory or morning wood. Men without physiological erect ...
.) The primary physiological mechanism that brings about erection is the autonomic dilation
Dilation (or dilatation) may refer to:
Physiology or medicine
* Cervical dilation, the widening of the cervix in childbirth, miscarriage etc.
* Coronary dilation, or coronary reflex
* Dilation and curettage, the opening of the cervix and surgic ...
of arteries
An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...
supplying blood to the penis, which allows more blood to fill the three spongy erectile tissue chambers in the penis, causing it to lengthen and stiffen. The now-engorged erectile tissue presses against and constricts the veins that carry blood away from the penis. More blood enters than leaves the penis until an equilibrium is reached where an equal volume of blood flows into the dilated arteries and out of the constricted veins; a constant erectile size is achieved at this equilibrium. The scrotum will usually tighten during erection.
Erection facilitates sexual intercourse though it is not essential for various other sexual activities.
Erection angle
Although many erect penises point upwards (see illustration), it is common and normal for the erect penis to point nearly vertically upwards or nearly vertically downwards or even horizontally straight forward, all depending on the tension of the suspensory ligament A suspensory ligament is a ligament that supports a body part, especially an organ.
Types include:
* Suspensory ligament of axilla, also known as Gerdy's ligament
* Cooper's ligaments, also known as the suspensory ligaments of Cooper or Suspensory ...
that holds it in position.
The following table shows how common various erection angles are for a standing male, out of a sample of 81 males aged 21 through 67. In the table, zero degrees is pointing straight up against the abdomen, 90 degrees is horizontal and pointing straight forward, while 180 degrees would be pointing straight down to the feet. An upward pointing angle is most common.
Ejaculation
Ejaculation is the ejection of semen from the penis. It is usually accompanied by orgasm
Orgasm (from Greek , ; "excitement, swelling") or sexual climax is the sudden discharge of accumulated sexual excitement during the sexual response cycle, resulting in rhythmic, involuntary muscular contractions in the pelvic region charac ...
. A series of muscular contractions delivers semen, containing male gametes
A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...
known as sperm cells or spermatozoa
A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, ...
, from the penis. Ejaculation usually happens as the result of sexual stimulation
Sexual stimulation is any stimulation, stimulus (including bodily contact) that leads to, enhances and maintains sexual arousal, and may lead to orgasm. Although sexual arousal may arise without physical stimulation, achieving orgasm usually requ ...
, but it can be due to prostatic disease
The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, chemically, and physi ...
in rare cases. Ejaculation may occur spontaneously during sleep (known as a nocturnal emission
A nocturnal emission, informally known as a wet dream, sex dream, nightfall or sleep orgasm, is a spontaneous orgasm during sleep that includes ejaculation for a male, or vaginal wetness or an orgasm (or both) for a female. Nocturnal emissions ...
or wet dream). Anejaculation is the condition of being unable to ejaculate.
Ejaculation has two phases: emission and ejaculation proper. The emission phase of the ejaculatory reflex is under control of the sympathetic nervous system
The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of th ...
, while the ejaculatory phase is under control of a spinal reflex
The stretch reflex (myotatic reflex), or more accurately "muscle stretch reflex", is a muscle contraction in response to stretching within the muscle. The reflex functions to maintain the muscle at a constant length. The term deep tendon reflex is ...
at the level of the spinal nerve
A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into th ...
s S2–4 via the pudendal nerve
The pudendal nerve is the main nerve of the perineum. It carries sensation from the external genitalia of both sexes and the skin around the anus and perineum, as well as the motor supply to various pelvic muscles, including the male or fem ...
. A refractory period succeeds the ejaculation, and sexual stimulation precedes it.
Evolved adaptations
The human penis has been argued to have several evolutionary adaptations. The purpose of these adaptations is to maximise reproductive success and minimise sperm competition
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and ...
. Sperm competition
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and ...
is where the sperm of two males simultaneously resides within the reproductive tract of a female and they compete to fertilise the egg. If sperm competition results in the rival male's sperm fertilising the egg, cuckold
A cuckold is the husband of an adulterous wife; the wife of an adulterous husband is a cuckquean. In biology, a cuckold is a male who unwittingly invests parental effort in juveniles who are not genetically his offspring. A husband who is aw ...
ry could occur. This is the process whereby males unwittingly invest their resources into offspring of another male and, evolutionarily speaking, should be avoided.
The most researched human penis adaptations are testis and penis size
Human penises vary in size on a number of measures, including length and circumference when flaccid and erect. Besides the natural variability of human penises in general, there are factors that lead to minor variations in a particular male, ...
, ejaculate adjustment and semen displacement.
Testis and penis size
Evolution has caused sexually selected adaptations to occur in penis
A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males do n ...
and testis size in order to maximise reproductive success and minimise sperm competition
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and ...
.
Sperm competition has caused the human penis to evolve in length and size for sperm retention and displacement. To achieve this, the penis must be of sufficient length to reach any rival sperm and to maximally fill the vagina. In order to ensure that the female retains the male's sperm, the adaptations in length of the human penis have occurred so that the ejaculate is placed close to the female cervix. This is achieved when complete penetration occurs and the penis pushes against the cervix. These adaptations have occurred in order to release and retain sperm to the highest point of the vaginal tract. As a result, this adaptation also leaves the sperm less vulnerable to sperm displacement and semen loss. Another reason for this adaptation is that, due to the nature of the human posture, gravity creates vulnerability for semen loss. Therefore, a long penis, which places the ejaculate deep in the vaginal tract, could reduce the loss of semen.
Another evolutionary theory of penis size is female mate choice
Mate choice is one of the primary mechanisms under which evolution can occur. It is characterized by a "selective response by animals to particular stimuli" which can be observed as behavior.Bateson, Paul Patrick Gordon. "Mate Choice." Mate Choic ...
and its associations with social judgements in modern-day society. A study which illustrates female mate choice as an influence on penis size presented females with life-size, rotatable, computer generated males. These varied in height, body shape and flaccid penis size, with these aspects being examples of masculinity. Female ratings of attractiveness for each male revealed that larger penises were associated with higher attractiveness ratings. These relations between penis size and attractiveness have therefore led to frequently emphasized associations between masculinity and penis size in popular media. This has led to a social bias existing around penis size with larger penises being preferred and having higher social status. This is reflected in the association between believed sexual prowess and penis size and the social judgement of penis size in relation to 'manhood'.
Like the penis, sperm competition has caused the human testicles to evolve in size through sexual selection
Sexual selection is a mode of natural selection in which members of one biological sex mate choice, choose mates of the other sex to mating, mate with (intersexual selection), and compete with members of the same sex for access to members of t ...
. This means that large testicles are an example of a sexually selected adaptation. The human testicles are moderately sized when compared to other animals such as gorillas and chimpanzees, placing somewhere midway. Large testicles are advantageous in sperm competition due to their ability to produce a bigger ejaculation. Research has shown that a positive correlation exists between the number of sperm ejaculated and testis size. Larger testes have also been shown to predict higher sperm quality, including a larger number of motile sperm and higher sperm motility.
Research has also demonstrated that evolutionary adaptations of testis size are dependent on the breeding system in which the species resides. Single-male breeding systems—or monogamous
Monogamy ( ) is a form of Dyad (sociology), dyadic Intimate relationship, relationship in which an individual has only one Significant other, partner during their lifetime. Alternately, only one partner at any one time (Monogamy#Serial monogamy, ...
societies—tend to show smaller testis size than do multi-male breeding systems or extra-pair copulation
Extra-pair copulation (EPC) is a mating behaviour in monogamous species. Monogamy is the practice of having only one sexual partner at any one time, forming a long-term bond and combining efforts to raise offspring together; mating outside this pai ...
(EPC) societies. Human males live largely in monogamous societies like gorillas, and therefore testis size is smaller in comparison to primates in multi-male breeding systems, such as chimpanzees. The reason for the differentiation in testis size is that in order to succeed reproductively in a multi-male breeding system, males must possess the ability to produce several fully fertilising ejaculations one after another. This, however, is not the case in monogamous societies, where a reduction in fertilising ejaculations has no effect on reproductive success. This is reflected in humans, as the sperm count in ejaculations is decreased if copulation occurs more than three to five times in a week.
Ejaculate adjustment
One of the primary ways in which a male's ejaculate has evolved to overcome sperm competition is through the speed at which it travels. Ejaculates can travel up to 30–60 centimetres at a time which, when combined with its placement at the highest point of the vaginal tract, acts to increase a male's chances that an egg will be fertilised by his sperm (as opposed to a potential rival male's sperm), thus maximising his paternal certainty.
In addition, males can—and do—adjust their ejaculates in response to sperm competition and according to the likely cost-benefits of mating with a particular female. Research has focused primarily on two fundamental ways in which males go about achieving this: adjusting ejaculate size and adjusting ejaculate quality.
Size
The number of sperm in any given ejaculate varies from one ejaculate to another. This variation is hypothesised to be a male's attempt to eliminate, if not reduce, his sperm competition
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and ...
. A male will alter the number of sperm he inseminates into a female according to his perceived level of sperm competition, inseminating a higher number of sperm if he suspects a greater level of competition from other males.
In support of ejaculate adjustment, research has shown that a male typically increases the amount he inseminates sperm into his partner after they have been separated for a period of time. This is largely due to the fact that the less time a couple is able to spend together, the chances the female will be inseminated by another male increases, hence greater sperm competition
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and ...
. Increasing the number of sperm a male inseminates into a female acts to get rid of any rival male's sperm that may be stored within the female, as a result of her potential extra-pair copulations
Extra-pair copulation (EPC) is a mating behaviour in monogamous species. Monogamy is the practice of having only one sexual partner at any one time, forming a long-term bond and combining efforts to raise offspring together; mating outside this pai ...
(EPCs) during this separation. Through increasing the amount he inseminates his partner following separation, a male increases his chances of paternal certainty. This increase in the number of sperm a male produces in response to sperm competition is not observed for masturbatory
Masturbation is the sexual stimulation of one's own Sex organ, genitals for sexual arousal or other sexual pleasure, usually to the point of orgasm. The stimulation may involve hands, fingers, everyday objects, sex toys such as vibrator (sex t ...
ejaculates.
Quality
Males also adjust their ejaculates in response to sperm competition in terms of quality. Research has demonstrated, for example, that simply viewing a sexually explicit image of a female and two males (i.e. high sperm competition) can cause males to produce a greater amount of motile sperm than when viewing a sexually explicit image depicting exclusively three females (i.e. low sperm competition). Much like increasing the number, increasing the quality of sperm that a male inseminates into a female enhances his paternal certainty when the threat of sperm competition is high.
Female phenotypic quality
A female's phenotypic
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...
quality is a key determinant of a male's ejaculate investment. Research has shown that males produce larger ejaculates containing better, more motile sperm when mating with a higher quality female. This is largely to reduce a male's sperm competition
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and ...
, since more attractive females are likely to be approached and subsequently inseminated by more males than are less attractive females. Increasing investment in females with high quality phenotypic traits therefore acts to offset the ejaculate investment of others. In addition, female attractiveness has been shown to be an indicator of reproductive quality, with greater value in higher quality females. It is therefore beneficial for males to increase their ejaculate size and quality when mating with more attractive females, since this is likely to maximise their reproductive success also. Through assessing a female's phenotypic quality, males can judge whether or not to invest (or invest more) in a particular female, which will influence their subsequent ejaculate adjustment.
Semen displacement
The shape of the human penis is thought to have evolved as a result of sperm competition. Semen displacement is an adaptation of the shape of the penis to draw foreign semen away from the cervix. This means that in the event of a rival male's sperm residing within the reproductive tract
The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical sex organs, organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pherom ...
of a female, the human penis is able to displace the rival sperm, replacing it with his own.
Semen displacement has two main benefits for a male. Firstly, by displacing a rival male's sperm, the risk of the rival sperm fertilising the egg is reduced, thus minimising the risk of sperm competition. Secondly, the male replaces the rival's sperm with his own, therefore increasing his own chance of fertilising the egg and successfully reproducing with the female. However, males have to ensure they do not displace their own sperm. It is thought that the relatively quick loss of erection after ejaculation, penile hypersensitivity following ejaculation, and the shallower, slower thrusting of the male after ejaculation, prevents this from occurring.
The coronal ridge is the part of the human penis thought to have evolved to allow for semen displacement. Research has studied how much semen is displaced by differently shaped artificial genitals. This research showed that, when combined with thrusting, the coronal ridge of the penis is able to remove the seminal fluid of a rival male from within the female reproductive tract
The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical sex organs, organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pherom ...
. It does this by forcing the semen under the frenulum
A frenulum (or frenum, plural: frenula or frena, from the Latin ''frēnulum'', "little bridle", the diminutive of ''frēnum'') is a small fold of tissue that secures the motion of a mobile organ in the body.
In human anatomy
Frenula on the h ...
of the coronal ridge, causing it to collect behind the coronal ridge shaft. When model penises without a coronal ridge were used, less than half the artificial sperm was displaced, compared to penises with a coronal ridge.
The presence of a coronal ridge alone, however, is not sufficient for effective semen displacement. It must be combined with adequate thrusting to be successful. It has been shown that the deeper the thrusting, the larger the semen displacement. No semen displacement occurs with shallow thrusting. Some have therefore termed thrusting as a semen displacement behaviour.
The behaviours associated with semen displacement, namely thrusting (number of thrusts and depth of thrusts), and duration of sexual intercourse
Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetrat ...
, have been shown to vary according to whether a male perceives the risk of partner infidelity
Infidelity (synonyms include cheating, straying, adultery, being unfaithful, two-timing, or having an affair) is a violation of a couple's emotional and/or sexual exclusivity that commonly results in feelings of anger, sexual jealousy, and riva ...
to be high or not. Males and females report greater semen displacement behaviours following allegations of infidelity. In particular, following allegations of infidelity, males and females report deeper and quicker thrusting during sexual intercourse.
Circumcision has been suggested to affect semen displacement. Circumcision causes the coronal ridge to be more pronounced, and it has been hypothesised that this could enhance semen displacement. This is supported by females' reports of sexual intercourse with circumcised males. Females report that their vaginal secretions
Vaginal lubrication is a naturally produced fluid that lubricates a
vagina. Vaginal lubrication is always present, but production increases significantly near ovulation and during sexual arousal in anticipation of sexual intercourse. Vaginal ...
diminish as intercourse with a circumcised male progresses, and that circumcised males thrust more deeply. It has therefore been suggested that the more pronounced coronal ridge, combined with the deeper thrusting, causes the vaginal secretions of the female to be displaced in the same way as rival sperm
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...
can be.
Clinical significance
Disorders
*Paraphimosis
Paraphimosis is an uncommon medical condition in which the foreskin of a penis becomes trapped behind the glans penis, and cannot be ''reduced'' (pulled back to its normal flaccid position covering the glans). If this condition persists for several ...
is an inability to move the foreskin forward over the glans. It can result from fluid trapped in a foreskin left retracted, perhaps following a medical procedure, or accumulation of fluid in the foreskin because of friction during vigorous sexual activity.
*In Peyronie's disease
Peyronie's disease is a connective tissue disorder involving the growth of fibrous plaques in the soft tissue of the penis. Specifically, scar tissue forms in the tunica albuginea, the thick sheath of tissue surrounding the corpora cavernosa, ca ...
, anomalous scar tissue grows in the soft tissue of the penis, causing curvature. Severe cases can be improved by surgical correction.
*A thrombosis
Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thro ...
can occur during periods of frequent and prolonged sexual activity, especially fellatio
Fellatio (also known as fellation, and in slang as blowjob, BJ, giving head, or sucking off) is an oral sex act involving a person stimulating the penis of another person by using the mouth, throat, or both. Oral stimulation of the scrotum may ...
. It is usually harmless and self-corrects within a few weeks.
*Infection with the herpes
Herpes simplex is a viral infection caused by the herpes simplex virus. Infections are categorized based on the part of the body infected.
Oral herpes involves the face or mouth. It may result in small blisters in groups often called cold s ...
virus can occur after sexual contact with an infected carrier; this may lead to the development of herpes sores.
*Balanitis
Balanitis is inflammation of the glans penis. When the foreskin is also affected, the proper term is balanoposthitis. Balanitis on boys still in diapers must be distinguished from redness caused by ammoniacal dermatitis. The word ''balanitis'' is ...
is an inflammation, either infectious or not.
*Pudendal nerve entrapment
Pudendal nerve entrapment (PNE), also known as Alcock canal syndrome, is an uncommon source of chronic pain in which the pudendal nerve (located in the pelvis) is entrapped or compressed in Alcock's canal. There are several different types of P ...
is a condition characterized by pain on sitting and the loss of penile sensation and orgasm. Occasionally there is a total loss of sensation and orgasm. The pudendal nerve
The pudendal nerve is the main nerve of the perineum. It carries sensation from the external genitalia of both sexes and the skin around the anus and perineum, as well as the motor supply to various pelvic muscles, including the male or fem ...
can be damaged by narrow, hard bicycle seats and accidents. This can also occur in the clitoris of females.
*Penile fracture
Penile fracture is rupture of one or both of the '' tunica albuginea'', the fibrous coverings that envelop the penis's '' corpora cavernosa''. It is caused by rapid blunt force to an erect penis, usually during vaginal intercourse, or aggressive ...
can occur if the erect penis is bent excessively. A popping or cracking sound and pain is normally associated with this event. Emergency medical assistance should be obtained as soon as possible. Prompt medical attention lowers the likelihood of permanent penile curvature.
*In diabetes
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
, peripheral neuropathy
Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or or ...
can cause tingling in the penile skin and possibly reduced or completely absent sensation. The reduced sensations can lead to injuries for either partner and their absence can make it impossible to have sexual pleasure through stimulation of the penis. Since the problems are caused by permanent nerve damage, preventive treatment through good control of the diabetes is the primary treatment. Some limited recovery may be possible through improved diabetes control.
*Erectile dysfunction
Erectile dysfunction (ED), also called impotence, is the type of sexual dysfunction in which the penis fails to become or stay erect during sexual activity. It is the most common sexual problem in men.Cunningham GR, Rosen RC. Overview of male ...
is the inability to develop and maintain an erection sufficiently firm for satisfactory sexual performance. Diabetes is a leading cause, as is natural aging. A variety of treatments exist, most notably including the phosphodiesterase type 5 inhibitor drugs (such as ''sildenafil
Sildenafil, sold under the brand name Viagra, among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. It is unclear if it is effective for treating sexual dysfunction in women. It is taken by ...
citrate'', marketed as Viagra), which work by vasodilation
Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstriction, ...
.
*Priapism
Priapism is a condition in which a penis remains erect for hours in the absence of stimulation or after stimulation has ended. There are three types: ischemic (low-flow), nonischemic (high-flow), and recurrent ischemic (intermittent). Most cases ...
is a painful and potentially harmful medical condition in which the erect penis does not return to its flaccid state. Priapism lasting over four hours is a medical emergency. The causative mechanisms are poorly understood but involve complex neurological and vascular factors. Potential complications include ischaemia
Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems wi ...
, thrombosis
Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thro ...
, and impotence
Erectile dysfunction (ED), also called impotence, is the type of sexual dysfunction in which the penis fails to become or stay erect during sexual activity. It is the most common sexual problem in men.Cunningham GR, Rosen RC. Overview of male ...
. In serious cases the condition may result in gangrene
Gangrene is a type of tissue death caused by a lack of blood supply. Symptoms may include a change in skin color to red or black, numbness, swelling, pain, skin breakdown, and coolness. The feet and hands are most commonly affected. If the ga ...
, which may result in amputation
Amputation is the removal of a limb by trauma, medical illness, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on indi ...
. However, that is usually only the case if the organ is broke out and injured because of it. The condition has been associated with a variety of drugs including prostaglandin
The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are derive ...
. Contrary to common knowledge, sildenafil
Sildenafil, sold under the brand name Viagra, among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. It is unclear if it is effective for treating sexual dysfunction in women. It is taken by ...
(Viagra) will not cause it.
*Lymphangiosclerosis
Sclerosing lymphangitis, also known as lymphangiosclerosis or sclerotic lymphangitis, is a skin condition characterized by a cordlike structure encircling the coronal sulcus of the penis, or running the length of the shaft, that has been attributed ...
is a hardened lymph vessel
The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessel ...
, although it can feel like a hardened, almost calcified or fibrous, vein. It tends not to share the common blue tint with a vein however. It can be felt as a hardened lump or "vein" even when the penis is flaccid, and is even more prominent during an erection. It is considered a benign
Malignancy () is the tendency of a medical condition to become progressively worse.
Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous benign tumor, ''benign'' tumor in that a malign ...
physical condition. It is fairly common and can follow a particularly vigorous sexual activity for men, and tends to go away if given rest and more gentle care, for example by use of lubricants.
* Carcinoma of the penis is rare with a reported rate of 1 person in 100,000 in developed countries. Some sources state that circumcision can protect against this disease, but this notion remains controversial among medical circles.
Developmental disorders
*Hypospadias
Hypospadias is a common variation in fetal development of the penis in which the urethra does not open from its usual location in the head of the penis. It is the second-most common birth abnormality of the male reproductive system, affecting abou ...
is a developmental disorder
Developmental disorders comprise a group of psychiatric conditions originating in childhood that involve serious impairment in different areas. There are several ways of using this term. The most narrow concept is used in the category "Specific Di ...
where the meatus
In anatomy, a meatus (, ),''OED'' 2nd edition, 1989, as . plural "meatus" or "meatuses", is positioned wrongly at birth. Hypospadias can also occur iatrogenically by the downward pressure of an indwelling urethral catheter. It is usually corrected by surgery.
*A micropenis
Micropenis is an unusually small penis. A common criterion is a dorsal (measured on top) penile length of at least 2.5 standard deviations smaller than the mean human penis size (stretched penile length less than 9.3 cm (3.67 in) in adults). ...
is a very small penis caused by developmental or congenital problems.
*Diphallia
Diphallia, penile duplication (PD), diphallic terata, or diphallasparatus, is an extremely rare developmental abnormality in which a male is born with two penises. The first reported case was by Johannes Jacob Wecker in 1609. Its occurrence is 1 ...
, or penile duplication (PD), is the rare condition of having two penises.
Alleged and observed psychological disorders
*Penis panic
Koro is a culture bound delusional disorder in which individuals have an overpowering belief that their sex organs are retracting and will disappear, despite the lack of any true longstanding changes to the genitals. Koro is also known as shri ...
(''koro'' in Malaysian
Malaysian may refer to:
* Something from or related to Malaysia, a country in Southeast Asia
* Malaysian Malay, a dialect of Malay language spoken mainly in Malaysia
* Malaysian people, people who are identified with the country of Malaysia regard ...
/Indonesian
Indonesian is anything of, from, or related to Indonesia, an archipelagic country in Southeast Asia. It may refer to:
* Indonesians, citizens of Indonesia
** Native Indonesians, diverse groups of local inhabitants of the archipelago
** Indonesian ...
)—delusion of shrinkage of the penis and retraction into the body. This appears to be culturally conditioned and largely limited to Ghana, Sudan, China, Japan, Southeast Asia, and West Africa.
* In April 2008, Kinshasa
Kinshasa (; ; ln, Kinsásá), formerly Léopoldville ( nl, Leopoldstad), is the capital and largest city of the Democratic Republic of the Congo. Once a site of fishing and trading villages situated along the Congo River, Kinshasa is now one o ...
, Democratic Republic of Congo, West Africa's 'Police arrested 14 suspected victims (of penis snatching) and sorcerers accused of using black magic or witchcraft to steal (make disappear) or shrink men's penises to extort cash for cure, amid a wave of panic. Arrests were made in an effort to avoid bloodshed seen in Ghana a decade before, when 12 penis snatchers were beaten to death by mobs.
*Penis envy
Penis envy (german: Penisneid) is a stage theorized by Sigmund Freud regarding female psychosexual development, in which young girls experience anxiety upon realization that they do not have a penis. Freud considered this realization a defining m ...
—the contested Freudian
Sigmund Freud ( , ; born Sigismund Schlomo Freud; 6 May 1856 – 23 September 1939) was an Austrian neurologist and the founder of psychoanalysis, a clinical method for evaluating and treating pathologies explained as originating in conflicts i ...
belief of all women inherently envying men for having penises.
Society and culture
Terminology
In many cultures, referring to the penis is considered taboo or vulgar, and a variety of slang words and euphemisms are used to talk about it. In English, these include ''member'', ''dick
Dick, Dicks, or Dick's may refer to:
Media
* ''Dicks'' (album), a 2004 album by Fila Brazillia
* Dicks (band), a musical group
* ''Dick'' (film), a 1999 American comedy film
* "Dick" (song), a 2019 song by Starboi3 featuring Doja Cat
Names
...
'', ''cock'', ''prick'', ''johnson'', ''dork'', ''peter'', ''pecker'', ''manhood'', ''stick'', ''rod'', ''thing'', ''third/middle leg'', ''dong'', ''willy'', ''schlong'', and ''todger.'' Many of these are used as insult
An insult is an expression or statement (or sometimes behavior) which is disrespectful or scornful. Insults may be intentional or accidental. An insult may be factual, but at the same time pejorative, such as the word "inbred".
Jocular exc ...
s—though sometimes playfully—meaning an unpleasant or unworthy person. Among these, historically, most commonly used euphemism for penis in English literature and society was ''member''.
Alteration
The penis is sometimes pierced or decorated by other body art. Other than circumcision, genital alterations are almost universally elective and usually for the purpose of aesthetics or increased sensitivity. Piercings of the penis include the Prince Albert, the apadravya
The apadravya, like the ampallang, is a piercing that passes through the glans. While the ampallang passes horizontally through the glans, the apadravya passes vertically through the glans from top to bottom, almost always placed centrally and pa ...
, the ampallang
The palang ( iba, crossbar), or ampallang is a male genital piercing that penetrates horizontally through the entire glans of the penis.
History
Penis piercings of proto-Malay origin predated European contact with tribes in (among others) the ...
, the dydoe
A dydoe is a type of male genital body piercing that passes through the ridge of the glans on the head of the penis. They are often done in pairs. Less often, a "king's crown" is where several dydoes are placed around the head of the penis. The ...
, and the frenum piercing
A frenum piercing is a type of body piercing located on the underside of the shaft of the penis. A series of parallel frenum piercings is known as a frenum ladder. A frenum ladder may be extended to include lorum piercings, hafada piercings and g ...
. Foreskin restoration
Foreskin restoration is the process of expanding the skin on the penis to reconstruct an organ similar to the foreskin, which has been removed by circumcision or injury. Foreskin restoration is primarily accomplished by stretching the residual ski ...
or stretching is a further form of body modification, as well as implants under the shaft of the penis.
Trans women
A trans woman or a transgender woman is a woman who was assigned male at birth. Trans women have a female gender identity, may experience gender dysphoria, and may transition; this process commonly includes hormone replacement therapy and so ...
who undergo sex reassignment surgery
Gender-affirming surgery (GAS) is a surgical procedure, or series of procedures, that alters a transgender or transsexual person's physical appearance and sexual characteristics to resemble those associated with their identified gender, and alle ...
have their penis surgically modified into a vagina via vaginoplasty
Vaginoplasty is any surgical procedure that results in the construction or reconstruction of the vagina. It is a type of genitoplasty. Pelvic organ prolapse is often treated with one or more surgeries to repair the vagina. Sometimes a vaginoplas ...
. Trans men
A trans man is a man who was assigned female at birth. The label of transgender man is not always interchangeable with that of transsexual man, although the two labels are often used in this way. ''Transgender'' is an umbrella term that incl ...
who undergo such surgery have a phalloplasty
Phalloplasty is the construction or reconstruction of a penis or the artificial modification of the penis by surgery. The term is also occasionally used to refer to penis enlargement.
History
Russian surgeon Nikolaj Bogoraz performed the firs ...
.
Other practices that alter the penis are also performed, although they are rare in Western societies without a diagnosed medical condition. Apart from penectomy
Penectomy is penis removal through surgery, generally for medical or personal reasons.
Medical reasons for penectomy
Cancer, for example, sometimes necessitates removal of part or all of the penis. The amount of penis removed depends on the se ...
, perhaps the most radical of these is subincision
Penile subincision is a form of genital modification or mutilation consisting of a urethrotomy, in which the underside of the penis is incised and the urethra slit open lengthwise, from the urethral opening (meatus) toward the base. The slit can ...
, in which the urethra is split along the underside of the penis. Subincision originated among Australian Aborigines
Aboriginal Australians are the various Indigenous peoples of the Australian mainland and many of its islands, such as Tasmania, Fraser Island, Hinchinbrook Island, the Tiwi Islands, and Groote Eylandt, but excluding the Torres Strait Islands ...
, although it is now done by some in the U.S. and Europe.
Circumcision
The most common form of body modification related to the penis is circumcision
Circumcision is a surgical procedure, procedure that removes the foreskin from the human penis. In the most common form of the operation, the foreskin is extended with forceps, then a circumcision device may be placed, after which the foreskin ...
: removal of part or all of the foreskin. It is most commonly performed as an elective procedure
Elective surgery or elective procedure (from the la, eligere, meaning to choose) is surgery that is scheduled in advance because it does not involve a medical emergency. Semi-elective surgery is a surgery that must be done to preserve the patie ...
for prophylactic
Preventive healthcare, or prophylaxis, consists of measures taken for the purposes of disease prevention.Hugh R. Leavell and E. Gurney Clark as "the science and art of preventing disease, prolonging life, and promoting physical and mental hea ...
, cultural
Culture () is an umbrella term which encompasses the social behavior, institutions, and Social norm, norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, and habits of the ...
, or religious
Religion is usually defined as a social system, social-cultural system of designated religious behaviour, behaviors and practices, morality, morals, beliefs, worldviews, religious text, texts, sacred site, sanctified places, prophecy, prophecie ...
reasons. For infant circumcision, modern devices such as the Gomco clamp
Circumcision surgical procedure in males involves either a conventional "cut and stitch" surgical procedure or use of a circumcision instrument or device. In the newborn period (less than 2 months of age), almost all circumcisions are done by g ...
, Plastibell
Circumcision surgical procedure in males involves either a conventional "cut and stitch" surgical procedure or use of a circumcision instrument or device. In the newborn period (less than 2 months of age), almost all circumcisions are done by ...
, and Mogen clamp
Circumcision surgical procedure in males involves either a conventional "cut and stitch" surgical procedure or use of a circumcision Surgical instrument, instrument or Medical device, device. In the newborn period (less than 2 months of age), alm ...
are available.
With all modern devices the same basic procedure is followed. First, the amount of foreskin to be removed is estimated. The foreskin is then opened via the preputial orifice to reveal the glans underneath and ensured that it is normal. The inner lining of the foreskin (preputial epithelium) is then separated from its attachment to the glans. The device is then placed (this sometimes requires a dorsal slit) and remains there until blood flow has stopped. Finally, part, or all, of the foreskin is then removed. Adult circumcisions are often performed without clamps and require 4 to 6 weeks of abstinence from masturbation or intercourse after the operation to allow the wound to heal. In some African countries, male circumcision is often performed by non-medical personnel under non-sterile conditions. After hospital circumcision, the foreskin may be used in biomedical research, consumer skin-care products, skin grafts, or β-interferon-based drugs. In parts of Africa, the foreskin may be dipped in brandy and eaten by the patient, eaten by the circumciser, or fed to animals. According to Jewish law
''Halakha'' (; he, הֲלָכָה, ), also Romanization of Hebrew, transliterated as ''halacha'', ''halakhah'', and ''halocho'' ( ), is the collective body of Judaism, Jewish religious laws which is derived from the Torah, written and Oral Tora ...
, after a ''Brit milah
The ''brit milah'' ( he, בְּרִית מִילָה ''bərīṯ mīlā'', ; Ashkenazi Hebrew, Ashkenazi pronunciation: , "Covenant (religion), covenant of circumcision"; Yiddish pronunciation: ''bris'' ) is Religion and circumcision, the cerem ...
'', the foreskin should be buried. Circumcision plays a major role in many of the world's cultures and religions. When performed for religious reasons, it is most common among both Jews
Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
and Muslims
Muslims ( ar, المسلمون, , ) are people who adhere to Islam, a monotheistic religion belonging to the Abrahamic tradition. They consider the Quran, the foundational religious text of Islam, to be the verbatim word of the God of Abraha ...
, among whom it is near-universal.
There are variant cultural, social, ethical, and religious views on circumcision. Among the world's major medical organizations, there is an overwhelming consensus that circumcision reduces heterosexual HIV infection rates in high-risk populations, and differing perspectives on the prophylactic efficacy and cost effectiveness
Cost-effectiveness analysis (CEA) is a form of economic analysis that compares the relative costs and outcomes (effects) of different courses of action. Cost-effectiveness analysis is distinct from cost–benefit analysis, which assigns a monetar ...
of circumcision in developed nations
A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state that has a high quality of life, developed economy and advanced technological infrastruct ...
. The World Health Organization (WHO; 2007), the Joint United Nations Programme on HIV/AIDS
The Joint United Nations Programme on HIV and AIDS (UNAIDS) (, ONUSIDA) is the main advocate for accelerated, comprehensive and coordinated global action on the HIV/AIDS pandemic.
The mission of UNAIDS is to lead, strengthen and support an e ...
(UNAIDS; 2007), and the Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
(CDC; 2008) state that evidence indicates circumcision significantly reduces the risk of HIV
The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...
acquisition by men during penile-vaginal sex, but also state that circumcision only provides partial protection and should not replace other interventions to prevent transmission of HIV.[
]
In 2010, the World Health Organization released a statement encouraging a higher rate of circumcision:There are significant benefits in performing male circumcision in early infancy, and programmes that promote early infant male circumcision are likely to have lower morbidity rates and lower costs than programmes targeting adolescent boys and men.
''Bolnick, Koyle & Yosha (2012)'' projects that worldwide circumcision rates will significantly rise "in the first half of the twenty-first century".
Potential regeneration
There are efforts by scientists to partially or fully regenerate the structures of the human penis. Patients who can benefit most from this field are those who have congenital defects, cancer, and injuries that have excised parts of their genitalia
A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...
. Some organizations which perform research into, or conduct regeneration procedures, include the Wake Forest Institute for Regenerative Medicine
The Wake Forest Institute for Regenerative Medicine (WFIRM) is a research institute affiliated with Wake Forest School of Medicine and located in Winston-Salem, North Carolina, United States
WFIRM's goal is to apply the principles of regenerative ...
and the United States Department of Defense
The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national secu ...
. The first successful penis allotransplant
Allotransplant (''allo-'' meaning "other" in Greek) is the transplantation of cells, tissues, or organs to a recipient from a genetically non-identical donor of the same species. The transplant is called an allograft, allogeneic transplant, o ...
surgery was done in September 2005 in a military hospital in Guangzhou
Guangzhou (, ; ; or ; ), also known as Canton () and alternatively romanized as Kwongchow or Kwangchow, is the capital and largest city of Guangdong province in southern China. Located on the Pearl River about north-northwest of Hong Kon ...
, China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
. A man at 44 sustained an injury after an accident and his penis was severed; urination
Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...
became difficult as his urethra was partly blocked. A recently brain-dead man, aged 23, was selected for the transplant. Despite atrophy
Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations (which can destroy the gene to build up the organ), poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply t ...
of blood vessels and nerves, the arteries
An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...
, veins
Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...
, nerves and the corpora spongiosa were successfully matched. But, on 19 September (after two weeks), the surgery was reversed because of a severe psychological
Psychology is the scientific study of mind and behavior. Psychology includes the study of conscious and unconscious phenomena, including feelings and thoughts. It is an academic discipline of immense scope, crossing the boundaries between t ...
problem (rejection) by the recipient and his wife. In 2009 researchers Chen, Eberli, Yoo and Atala have produced bioengineered
Biological engineering or
bioengineering is the application of principles of biology and the tools of engineering to create usable, tangible, economically-viable products. Biological engineering employs knowledge and expertise from a number o ...
penises and implanted them on rabbits. The animals were able to obtain erection
An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged. Penile erection is the result of a complex interaction of psychological, neural, vascular, ...
and copulate
Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetr ...
, with 10 of 12 rabbits achieving ejaculation
Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential componen ...
. This study shows that in the future it could be possible to produce artificial penises for replacement surgeries or phalloplasties. In 2015 the world's first successful penis transplant took place in Cape Town
Cape Town ( af, Kaapstad; , xh, iKapa) is one of South Africa's three capital cities, serving as the seat of the Parliament of South Africa. It is the legislative capital of the country, the oldest city in the country, and the second largest ...
, South Africa in a nine-hour operation performed by surgeons from Stellenbosch University
Stellenbosch University ( af, Universiteit Stellenbosch) is a public research university situated in Stellenbosch, a town in the Western Cape province of South Africa. Stellenbosch is the oldest university in South Africa and the oldest extant ...
and Tygerberg Hospital
Tygerberg Hospital is a tertiary hospital located in Parow. The hospital was officially opened in 1976 and is the largest hospital in the Western Cape and the second largest hospital in South Africa, with the capacity for 1899 beds. It acts as ...
. The 21-year-old recipient, who had been sexually active, had lost his penis in a botched circumcision at 18.
Additional images
Image:Sobo 1906 490.png, Dissection showing the fascia of the penis as well as several surrounding structures
Image:Sobo 1909 571.png, Image showing innervation and blood-supply of the human male external genitalia
References
External links
Kinsey Institute on the penis
{{Authority control
Human anatomy
Men's health
Urinary system