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A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that
male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to ...
animals use to inseminate females (or hermaphrodites) during
copulation 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 penetra ...
. Such organs occur in many animals, both vertebrate and
invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...
, but males do not bear a penis in every animal species, and in those species in which the male does bear a so-called penis, the penises in the various species are not necessarily homologous. The term ''penis'' applies to many intromittent organs, but not to all. As an example, the intromittent organ of most cephalopoda is the hectocotylus, a specialized arm, and male spiders use their pedipalps. Even within the Vertebrata there are morphological variants with specific terminology, such as hemipenes. In most species of animals in which there is an organ that might reasonably be described as a penis, it has no major function other than intromission, or at least conveying the sperm to the female, but in the placental mammals the penis bears the distal part of 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 ...
, which discharges both
urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...
during urination and semen during copulation.


Vertebrates


Birds

Most male birds (e.g., roosters and
turkey Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a transcontinental country located mainly on the Anatolian Peninsula in Western Asia, with a small portion on the Balkan Peninsula ...
s) have a cloaca (also present on the female), but not a penis. Among bird species with a penis are paleognathes (
tinamou Tinamous () form an order of birds called Tinamiformes (), comprising a single family called Tinamidae (), divided into two distinct subfamilies, containing 46 species found in Mexico, Central America, and South America. The word "tinamou" co ...
s and ratites) and
Anatidae The Anatidae are the biological family of water birds that includes ducks, geese, and swans. The family has a cosmopolitan distribution, occurring on all the world's continents except Antarctica. These birds are adapted for swimming, flo ...
(ducks, geese and swans). A bird penis is different in structure from mammal penises, being an erectile expansion of the cloacal wall and being erected by
lymph Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues ...
, not blood. It is usually partially feathered and in some species features spines and brush-like filaments, and in flaccid state curls up inside the cloaca. While most male birds have no external genitalia, male waterfowl (
Anatidae The Anatidae are the biological family of water birds that includes ducks, geese, and swans. The family has a cosmopolitan distribution, occurring on all the world's continents except Antarctica. These birds are adapted for swimming, flo ...
) have a phallus. Most birds mate with the males balancing on top of the females and touching cloacas in a "cloacal kiss"; this makes forceful insemination very difficult. The phallus that male waterfowl have evolved everts out of their bodies (in a clockwise coil) and aids in inseminating females without their cooperation.Brennan, P. L. R. et al. Coevolution of male and female genital morphology in waterfowl. ''PLoS ONE'' 2, e418 (2007). The male waterfowl evolution of a phallus to forcefully copulate with females has led to counteradaptations in females in the form of vaginal structures called dead end sacs and clockwise coils. These structures make it harder for males to achieve intromission. The clockwise coils are significant because the male phallus everts out of their body in a counter-clockwise spiral; therefore, a clockwise vaginal structure would impede forceful copulation. Studies have shown that the longer a male's phallus is, the more elaborate the vaginal structures were. The lake duck is notable for possessing, in relation to body length, the longest penis of all vertebrates; the penis, which is typically coiled up in flaccid state, can reach about the same length as the animal himself when fully erect, but is more commonly about half the bird's length. It is theorized that the remarkable size of their spiny penises with bristled tips may have evolved in response to competitive pressure in these highly promiscuous birds, removing sperm from previous matings in the manner of a bottle brush. The lake duck has a corkscrew shaped penis. Male and female emus are similar in appearance,Eastman, p. 23. although the male's penis can become visible when it defecates.Coddington and Cockburn, p. 366. The male tinamou has a corkscrew shaped penis, similar to those of the ratites and to the hemipenis of some reptiles. Females have a small phallic organ in the cloaca which becomes larger during the breeding season.


Mammals

As with any other bodily attribute, the length and girth of the penis can be highly variable between mammals of different
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
. In many mammals, the size of a flaccid penis is smaller than its erect size. A bone called the
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 ''os penis'' is present in most mammals but absent in humans, cattle and horses. In mammals the penis is divided into three parts: * Roots ( crura): these begin at the caudal border of the pelvic ischial arch. * Body: the part of the penis extending from the roots. * Glans: the free end of the penis. The internal structures of the penis consist mainly of cavernous, erectile tissue, which is a collection of blood sinusoids separated by sheets of connective tissue (trabeculae). Some mammals have a lot of erectile tissue relative to connective tissue, for example horses. Because of this a
horse's penis A stallion is a male horse that has not been gelded (castrated). Stallions follow the conformation and phenotype of their breed, but within that standard, the presence of hormones such as testosterone may give stallions a thicker, "cresty" nec ...
can enlarge more than a bull's 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 ...
is on the ventral side of the body of the penis. As a general rule, a mammal's penis is proportional to its body size, but this varies greatly between specieseven between closely related ones. For example, an adult
gorilla Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four ...
's erect penis is about in length; an adult chimpanzee, significantly smaller (in body size) than a gorilla, has a penis size about double that of the gorilla. In comparison, the human penis is larger than that of any other
primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter includin ...
, both in proportion to body size and in absolute terms.


Artiodactyls

The penises of even-toed ungulates are curved in an S-shape when not erect. In bulls, rams and
boar The wild boar (''Sus scrofa''), also known as the wild swine, common wild pig, Eurasian wild pig, or simply wild pig, is a suid native to much of Eurasia and North Africa, and has been introduced to the Americas and Oceania. The species is ...
s, the sigmoid flexure of the penis straightens out during erection. When mating, the tip of a male pronghorn's penis is often the first part to touch the female pronghorn. The pronghorn's penis is about long, and is shaped like an ice pick. The front of a pronghorn's glans penis is relatively flat, while the back is relatively thick. The male pronghorn usually ejaculates immediately after intromission. The penis of a
dromedary The dromedary (''Camelus dromedarius'' or ;), also known as the dromedary camel, Arabian camel, or one-humped camel, is a large even-toed ungulate, of the genus '' Camelus'', with one hump on its back. It is the tallest of the three species o ...
camel is covered by a triangular penile sheath opening backwards, and is about long. The camelmen often aid the male to enter his penis into the female's
vulva The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external female sex organs. The vulva includes the mons pubis (or mons veneris), labia majora, labia minora, clitoris, vestibular bulbs, vulv ...
, though the male is considered able to do it on his own. Copulation time ranges from 7 to 35 minutes, averaging 11–15 minutes. Bulls have a fibro-elastic penis. Given the small amount of erectile tissue, there is little enlargement after erection. The penis is quite rigid when non-erect, and becomes even more rigid during erection. Protrusion is not affected much by erection, but more by relaxation of the retractor penis muscle and straightening of the
sigmoid flexure The sigmoid colon (or pelvic colon) is the part of the large intestine that is closest to the rectum and anus. It forms a loop that averages about in length. The loop is typically shaped like a Greek letter sigma (ς) or Latin letter S (thus ''s ...
. The male genitalia of mouse deer are similar to those of pigs. A boar's penis, which rotates rhythmically during copulation, is about long, and ejaculates about a pint of semen. Wild boars have a roughly egg-sized sack near the opening of the penis, which collects urine and emits a sharp odour. The purpose of this is not fully understood.Heptner, V. G.; Nasimovich, A. A.; Bannikov, A. G.; Hoffman, R. S. (1988
''Mammals of the Soviet Union''
Volume I, Washington, D.C. : Smithsonian Institution Libraries and National Science Foundation, pp. 19-82


=Deer

= A stag's penis forms an S-shaped curve when it is not erect, and is retracted into its sheath by the retractor penis muscle. Some deer species spray urine on their bodies by urinating from an erect penis. One type of scent-marking behavior in elk is known as "thrash-urination, which typically involves palpitation of the erect penis. A male elk's urethra points upward so that urine is sprayed almost at a right angle to the penis. A sambar stag will mark himself by spraying urine directly in the face with a highly mobile penis, which is often erect during its rutting activities.''Deer of the world: their evolution, behaviour, and ecology.'' Valerius Geist. Stackpole Books. 1998. Pg. 73-77.
Red deer The red deer (''Cervus elaphus'') is one of the largest deer species. A male red deer is called a stag or hart, and a female is called a hind. The red deer inhabits most of Europe, the Caucasus Mountains region, Anatolia, Iran, and parts of ...
stags often have erect penises during combat.


Cetaceans

Cetaceans' reproductive organs are located inside the body. Male cetaceans (whales, dolphins, and porpoises) have two slits, the genital groove concealing the penis and one further behind for the anus. Cetaceans have fibroelastic penises, similar to those of Artiodactyla. The tapering tip of the cetacean penis is called the ''pars intrapraeputialis'' or ''terminal cone''. The
blue whale The blue whale (''Balaenoptera musculus'') is a marine mammal and a baleen whale. Reaching a maximum confirmed length of and weighing up to , it is the largest animal known to have ever existed. The blue whale's long and slender body can ...
has the largest penis of any organism on the planet, typically measuring . Accurate measurements are difficult to take because its erect length can only be observed during mating, which occurs underwater. The penis on a right whale can be up to – the testes, at up to in length, in diameter, and weighing up to , are also by far the largest of any animal on Earth. On at least one occasion, a dolphin towed bathers through the water by hooking his erect penis around them. Between male bottlenose dolphins, homosexual behaviour includes rubbing of genitals against each other, which sometimes leads to the males swimming belly to belly, inserting the penis in the other's genital slit and sometimes anus.


Perissodactyls

Stallions (male horses) have a vascular penis. When non-erect, it is quite flaccid and contained within the prepuce (foreskin, or sheath). Tapirs have exceptionally long penises relative to their body size. The glans of the Malayan tapir resembles a mushroom, and is similar to the glans of the horse. The penis of the Sumatran rhinoceros contains two lateral lobes and a structure called the ''processus glandis''.


Carnivores

All members of Carnivora (except hyenas) have a baculum. Canine penises have a structure at the base called the
bulbus glandis The bulbus glandis (also called a bulb or knot) is an erectile tissue structure on the penis of canid mammals. During mating, immediately before ejaculation the tissues swell up to lock ('' tie'') the male's penis inside the female. The locking ...
. During copulation, the spotted hyena inserts his penis through the female's pseudo-penis instead of directly through the vagina, which is blocked by the false scrotum and testes. Once the female retracts her clitoris, the male enters the female by sliding beneath her, an operation facilitated by the penis's upward angle. The pseudo-penis closely resembles the male hyena's penis, but can be distinguished from the male's genitalia by its greater thickness and more rounded glans. In male spotted hyenas, as well as females, the base of the glans is covered with penile spines.
Domestic cats The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
have barbed penises, with about 120–150 one millimeter long backwards-pointing spines. Upon withdrawal of the penis, the spines rake the walls of the female's vagina, which is a trigger for ovulation. Lions also have barbed penises. Male felids urinate backwards by curving the tip of the glans penis backward. When male cheetahs urine-mark their territories, they stand one meter away from a tree or rock surface with the tail raised, pointing the penis either horizontally backward or 60° upward. The male fossa has an unusually long penis and
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 ...
(penis bone), reaching to between his
front leg A forelimb or front limb is one of the paired articulated appendages (limbs) attached on the cranial (anterior) end of a terrestrial tetrapod vertebrate's torso. With reference to quadrupeds, the term foreleg or front leg is often used inste ...
s when erect with backwards-pointing spines along most of its length. The male fossa has scent glands near the penis, with the penile glands emitting a strong odor. The beech marten's penis is larger than the pine marten's, with the
bacula Bacula is an open-source, enterprise-level computer backup system for heterogeneous networks. It is designed to automate backup tasks that had often required intervention from a systems administrator or computer operator. Bacula supports Li ...
of young beech martens often outsizing those of old pine martens. Raccoons have penis bones which bend at a 90 degree angle at the tip. The extrusibility of a raccoon's penis can be used to distinguish mature males from immature males. Male walruses possess the largest penis bones of any land mammal, both in absolute size and relative to body size. The adult male American mink's penis is long, and is covered by a
sheath Sheath pronounced as , may refer to: * Scabbard, a sheath for holding a sword, knife, or other large blade, as well as guns, such as rifles. * The outer covering of a cable * Condom, a kind of contraception * Debye sheath, a layer of a plasma ...
. The
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 ...
is well-developed, being triangular in cross section and curved at the tip.


Bats

Males of Racey's pipistrelle bat have a long, straight penis with a notch between the shaft and the narrow, egg-shaped glans penis. Near the top, the penis is haired, but the base is almost naked. In the
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 ...
(penis bone), the shaft is long and narrow and slightly curved. The length of the penis and baculum distinguish ''P. raceyi'' from all comparably sized African and Malagasy vespertilionids. In males, penis length is and baculum length is . Copulation by male
greater short-nosed fruit bat The greater short-nosed fruit bat (''Cynopterus sphinx''), or short-nosed Indian fruit bat, is a species of megabat in the family Pteropodidae found in South and Southeast Asia. Description These bats have a relatively long snout. Their upper p ...
s is dorsoventral and the females lick the shaft or the base of the male's penis, but not the glans which has already penetrated the vagina. While the females do this, the penis is not withdrawn and research has shown a positive relationship between length of the time that the penis is licked and the duration of copulation. Post copulation genital grooming has also been observed.


Rodents

The glans penis of the
marsh rice rat The marsh rice rat (''Oryzomys palustris'') is a semiaquatic North American rodent in the family Cricetidae. It usually occurs in wetland habitats, such as swamps and salt marshes. It is found mostly in the eastern and southern United States, fr ...
is long and robust, averaging long and broad, and the baculum (penis bone) is long. As is characteristic of
Sigmodontinae The rodent subfamily Sigmodontinae includes New World rats and mice, with at least 376 species. Many authorities include the Neotominae and Tylomyinae as part of a larger definition of Sigmodontinae. When those genera are included, the species c ...
, the marsh rice rat has a complex penis, with the distal (far) end of the baculum ending in three digits. The central digit is notably larger than those at the sides. The outer surface of the penis is mostly covered by small spines, but there is a broad band of nonspinous tissue. The papilla (nipple-like projection) on the dorsal (upper) side of the penis is covered with small spines, a character the marsh rice rat shares only with ''
Oligoryzomys ''Oligoryzomys'' is a genus of rodents in the tribe Oryzomyini of family Cricetidae. Many species are known as pygmy rice rats or colilargos.Musser and Carleton, 2005 The genus is found from Mexico to Tierra del Fuego and includes approximately 1 ...
'' and ''Oryzomys couesi'' among oryzomyines examined. On the urethral process, located in the crater at the end of the penis, a fleshy process (the subapical lobule) is present; it is absent in all other oryzomyines with studied penes except ''O. couesi'' and ''
Holochilus brasiliensis ''Holochilus brasiliensis'', also known as the Brazilian marsh ratMusser, G.G. and Carleton, M.D. 2005. Superfamily Muroidea. Pp. 894–1531 in Wilson, D.E. and Reeder, D.M. (eds.)Mammal Species of the World: a taxonomic and geographic refer ...
''. The baculum is deeper than it is wide. In ''
Transandinomys talamancae ''Transandinomys talamancae'' is a rodent in the family Cricetidae that occurs from Costa Rica to southwestern Ecuador and northern Venezuela. Its habitat consists of lowland forests up to above sea level. With a body mass of , it is a m ...
'', the outer surface of the penis is mostly covered by small spines, but there is a broad band of nonspinous tissue. Some features of the accessory glands in the male genital region vary among oryzomyines. In ''Transandinomys talamancae'', a single pair of
preputial gland Preputial glands are exocrine glands that are located in the folds of skin front of the genitals of some mammals. They occur in several species, including mice, ferrets, rhinoceroses, and even-toed ungulates and produce pheromones. The glands play ...
s is present at the penis. As is usual for sigmodontines, there are two pairs of ventral prostate glands and a single pair of anterior and dorsal prostate glands. Part of the end of the vesicular gland is irregularly folded, not smooth as in most oryzomyines. In
Pseudoryzomys ''Pseudoryzomys simplex'', also known as the Brazilian false rice rat or false oryzomys, is a species of rodent in the family Cricetidae from south-central South America. It is found in lowland palm savanna and thorn scrub habitats. It is a m ...
, the
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 ...
(penis bone) displays large protuberances at the sides. In the cartilaginous part of the baculum, the central digit is smaller than those at the sides. In
Drymoreomys ''Drymoreomys'' is a rodent genus in the tribe Oryzomyini that lives in the Atlantic Forest of Brazil. The single species, ''D. albimaculatus'', is known only from the states of São Paulo (state), São Paulo and Santa Catarina (state), San ...
, there are three digits at the tip of the penis, of which the central one is the largest. In '' Thomasomys ucucha'' the glans penis is rounded, short, and small and is superficially divided into left and right halves by a trough at the top and a ridge at the bottom. The glans penis of a male cape ground squirrel is large with a prominent baculum. Unlike other squirrel species, red squirrels have long, thin, and narrow penises, without a prominent baculum.
Winkelmann's mouse Winkelmann's mouse (''Peromyscus winkelmanni'') is a species of rodent in the family Cricetidae found only in Mexico, and is named for John R. Winkelmann, who collected the first specimens. Description Rather larger than a house mouse, an adult ...
can easily be distinguished from its close relatives by the shape of its penis, which has a partially corrugated glans. The foreskin of a capybara is attached to the anus in an unusual way, forming an anogenital invagination.


Primates

It has been postulated that the shape of the human penis may have been selected by sperm competition. The shape could have favored displacement of
seminal fluid 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 is ...
s implanted within the female reproductive tract by rival males: the thrusting action which occurs during sexual intercourse can mechanically remove seminal fluid out of the cervix area from a previous mating. The penile morphology of some types of strepsirrhine
primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter includin ...
s has provided information about their taxonomy. Male galago species possess very distinctive penile morphology that can be used to classify species. The northern greater galago penis is on average in length, with doubled headed or even tridentate spines pointing towards the body. They are less densely packed than in ''Otolemur crassicaudatus''. The penis of the ring-tailed lemur is nearly cylindrical in shape and is covered in small spines, as well as having two pairs of larger spines on both sides. The adult male of each vervet monkey species has a pale blue scrotum and a red penis, and male proboscis monkeys have a red penis with a black scrotum. Male
baboons Baboons are primates comprising the genus ''Papio'', one of the 23 genera of Old World monkeys. There are six species of baboon: the hamadryas baboon, the Guinea baboon, the olive baboon, the yellow baboon, the Kinda baboon and the chacma b ...
and
squirrel monkeys Squirrel monkeys are New World monkeys of the genus ''Saimiri''. ''Saimiri'' is the only genus in the subfamily Saimirinae. The name of the genus is of Tupi origin (''sai-mirím'' or ''çai-mbirín'', with ''sai'' meaning 'monkey' and ''mirím'' ...
sometimes gesture with an erect penis as both a warning of impending danger and a threat to predators. In male squirrel monkeys, this gesture is used for social communication.


=Humans

= The human penis is an external sex organ of
male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to ...
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
s. It is a reproductive, intromittent organ that additionally serves as the urinal duct. The main parts are the root of the penis (radix): It is the attached part, consisting of the bulb of penis 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; the body of the penis (corpus); and the epithelium 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 animal coverings, such as the arthropod exoskeleton, have different ...
, the foreskin, 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 ...
on the inside of the foreskin and covering the glans penis. 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 ...
and one corpus spongiosum 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
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 ...
, which is the last part of the urinary tract, traverses the corpus spongiosum, and its opening, known as the meatus , lies on the tip of the glans penis. It is a passage both for
urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...
and for the
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 compo ...
of semen. In males, the expulsion of
urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...
from the body is done through 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 ...
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 physi ...
where it is joined by the ejaculatory duct, and then onward to the penis. An erection is the stiffening and rising of the penis, which occurs during sexual arousal, though it can also happen in non-sexual situations. Ejaculation is the ejecting of semen from the penis and 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 chara ...
. A series of muscular contractions delivers semen, containing male gametes known as sperm cells or spermatozoa, from the penis. The most common form of genital alteration is
circumcision Circumcision is a 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 is excised. Top ...
, the removal of part or all of the foreskin for various cultural, religious, and more rarely medical reasons. There is controversy surrounding circumcision. , a systematic review of 15,521 men, who were measured by health professionals rather than themselves, 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).


Marsupials

Most marsupials, except for the two largest species of kangaroos and marsupial moles (assuming the latter are true marsupials), have a bifurcated penis, separated into two columns, so that the penis has two ends corresponding to the females' two vaginas.


Monotremes

Monotremes and marsupial moles are the only mammals in which the penis is located inside the cloaca. Male echidnas have a bilaterally symmetrical, rosette-like, four-headed penis. During mating, the heads on one side "shut down" and do not grow in size; the other two are used to release semen into the female's two-branched reproductive tract. The heads used are swapped each time the mammal copulates.Augee, Gooden and Musser, p. 81. When not in use, the penis is retracted inside a preputial sac in the cloaca. The male echidna's penis is long when erect, and its shaft is covered with penile spines. The penis is nearly a quarter of his body length when erect.


Others

The penis of the bush hyrax is complex and distinct from that of the other hyrax genera. It has a short, thin appendage within a cup-like glans penis and measures greater than when erect. Additionally, it has been observed that the bush hyrax also has a greater distance between the anus and preputial opening in comparison to other hyraxes. An adult elephant has the largest penis of any land animal. An elephant's penis can reach a length of and a diameter of at the base. It is S-shaped when fully erect and has a Y-shaped orifice. During musth, a male elephant may urinate with his penis still in the
sheath Sheath pronounced as , may refer to: * Scabbard, a sheath for holding a sword, knife, or other large blade, as well as guns, such as rifles. * The outer covering of a cable * Condom, a kind of contraception * Debye sheath, a layer of a plasma ...
, which causes the urine to spray on the hind legs.Sukumar, pp. 100–08. An elephant's penis is very mobile, being able to move independently of the male's pelvis, and the penis curves forward and upward prior to mounting another elephant. In giant anteaters, the (retracted) penis and testes are located internally between the rectum and urinary bladder. When the male armadillo ''
Chaetophractus villosus The big (or large) hairy armadillo (''Chaetophractus villosus'') is one of the largest and most numerous armadillos in South America. It lives from sea level to altitudes of up to 1,300 meters across the southern portion of South America, and ...
'' is sexually aroused, species determination is easier. Its penis can be as long as , and usually remains completely withdrawn inside a skin receptacle. Scientists conducting studies on the ''C. villosus'' penis muscles revealed this species' very long penis exhibits variability. During its waking hours, it remains hidden beneath a skin receptacle, until it becomes erect and it projects outside in a rostral direction.


Fish and reptiles

Male turtles and crocodiles have a penis, while male specimens of the reptile order
Squamata Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest order of reptiles, comprising lizards, snakes, and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. With over 10,900 species, ...
have two paired organs called hemipenes. Tuataras must use their cloacae for reproduction. Due to
evolutionary convergence Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
, turtle and mammal penises have a similar structure. In some fish, the gonopodium, andropodium, and claspers are intromittent organs (to introduce sperm into the female) developed from modified fins.


Invertebrates


Arthropods

The record for the largest penis size to body size ratio is held by the barnacle. The barnacle's penis can grow to up to forty times its own body length. This enables them to reach the nearest female for fertilization. A number of invertebrate species have independently evolved the mating technique of traumatic insemination where the penis penetrates the female's abdomen, thereby creating a womb into which it deposits sperm. This has been most fully studied in
bed bug Bed bugs are insects from the genus ''Cimex'' that feed on blood, usually at night. Their bites can result in a number of health impacts including skin rashes, psychological effects, and allergic symptoms. Bed bug bites may lead to skin changes ...
s. Some millipedes have penises. In these species, the penis is simply one or two projections on underneath the third body segment that produce a
spermatophore A spermatophore or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. Spermatophore ...
or sperm packet. The act of insemination, however, occurs through specialized legs called
gonopods Gonopods are specialized appendages of various arthropods used in reproduction or egg-laying. In males, they facilitate the transfer of sperm from male to female during mating, and thus are a type of intromittent organ. In crustaceans and millipe ...
which collect the spermatophore and insert it into the female.


Insects

In male
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s, the structure analogous to a penis is known as aedeagus. The male copulatory organ of various lower invertebrate animals is often called the ''cirrus''. The lesser water boatman's mating call, generated by rubbing the penis against the
abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...
, is the loudest sound, relative to body size, in the animal kingdom. In 2010, entomologist Charles Linehard described ''
Neotrogla ''Neotrogla'' is a genus of barklice noted for its reversed sex roles and organs, traits shared by all species of the genus. Habitat ''Neotrogla'' are found in dry cave systems throughout Brazil. They feed primarily on bat guano. Description ...
'', a new genus of barkflies. Species of this genus have sex-reversed genitalia. Females have penis-like organs called gynosomes that are inserted into vagina-like openings of males during mating. In 2014, a detailed study of the insects reproductive habits led by Kazunori Yoshizawae confirmed that the organ functions similar to a penis – for example, it swells during sexual intercourse – and is used to extract sperm from the male.


Mollusks

The penis in most male Coleoid
cephalopods A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, a ...
is a long and muscular end of the gonoduct used to transfer spermatophores to a modified arm called a hectocotylus. That, in turn, is used to transfer the spermatophores to the female. In species where the hectocotylus is missing, the penis is long and able to extend beyond the mantle cavity and transfers the spermatophores directly to the female. Deepwater squid have the greatest known penis length relative to body size of all mobile animals, second in the entire animal kingdom only to certain sessile barnacles Penis elongation in ''
Onykia ingens ''Onykia ingens'', the greater hooked squid, is a species of squid in the family Onychoteuthidae. It occurs worldwide in subantarctic oceans. Although ''O. ingens'' was long attributed to the genus ''Moroteuthis'', several authors have recently ...
'' may result in a penis that is as long as the mantle, head and arms combined.
Giant squid The giant squid (''Architeuthis dux'') is a species of deep-ocean dwelling squid in the family Architeuthidae. It can grow to a tremendous size, offering an example of abyssal gigantism: recent estimates put the maximum size at around Tra ...
of the genus '' Architeuthis'' are unusual in that they possess both a large penis and modified arm tips, although it is uncertain whether the latter are used for spermatophore transfer.


Etymology

The word "penis" is taken from the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
word for " tail". Some derive that from
Indo-European The Indo-European languages are a language family native to the overwhelming majority of Europe, the Iranian plateau, and the northern Indian subcontinent. Some European languages of this family, English, French, Portuguese, Russian, Du ...
''*pesnis'', and the Greek word πέος = "penis" from Indo-European ''*pesos''. Prior to the adoption of the Latin word in English the penis was referred to as a "yard". The
Oxford English Dictionary The ''Oxford English Dictionary'' (''OED'') is the first and foundational historical dictionary of the English language, published by Oxford University Press (OUP). It traces the historical development of the English language, providing a c ...
cites an example of the word ''yard'' used in this sense from 1379, and notes that in his ''Physical Dictionary'' of 1684,
Steven Blankaart Steven Blankaart (24 October 1650, Middelburg – 23 February 1704, Amsterdam) was a Dutch physician, iatrochemist, and entomologist, who worked on the same field as Jan Swammerdam. Blankaart proved the existence of a capillary system, a ...
defined the word ''penis'' as "the Yard, made up of two nervous Bodies, the Channel, Nut, Skin, and Fore-skin, etc." According t
Wiktionary
this term meant (among other senses) "rod" or "bar". As with nearly any aspect of the body involved in sexual or excretory functions, the penis is the subject of many
slang Slang is vocabulary (words, phrases, and linguistic usages) of an informal register, common in spoken conversation but avoided in formal writing. It also sometimes refers to the language generally exclusive to the members of particular in-gr ...
words and euphemisms for it, a particularly common and enduring one being "cock". See WikiSaurus:penis for a list of alternative words for penis. The Latin word ''"
phallus A phallus is a penis (especially when erect), an object that resembles a penis, or a mimetic image of an erect penis. In art history a figure with an erect penis is described as ithyphallic. Any object that symbolically—or, more precise ...
"'' (from Greek φαλλος) is sometimes used to describe the penis, although "phallus" originally was used to describe ''representations'', pictorial or carved, of the penis.


Heraldry

Pizzles are represented in heraldry, where the adjective ''pizzled'' (or ''vilené'') indicates that part of an animate charge's anatomy, especially if coloured differently.


See also

*
Buried penis Buried penis (also known as hidden penis or retractile penis) is a congenital or acquired condition in which the penis is partially or completely hidden below the surface of the skin. A buried penis can lead to urinary difficulties, poor hygiene, ...
* Castration anxiety *
Dildo A dildo is a sex toy, often explicitly phallic in appearance, intended for sexual penetration or other sexual activity during masturbation or with sex partners. Dildos can be made from a number of materials and shaped like an erect human penis ...
*
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 ...
*
Erogenous zone An erogenous zone (from Greek , ''érōs'' "love"; and English ''-genous'' "producing", from Greek , ''-genḗs'' "born") is an area of the human body that has heightened sensitivity, the stimulation of which may generate a sexual response, suc ...
* Fascinus * Koteka *
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 ...
* Penis enlargement * Penis envy * Penis removal * Phallic architecture * Preputioplasty * Pubic hair *
Stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the fila ...
* Stunt cock * Testicle


References


Citations


General and cited references


Horses

* * * * * * * * *


Marsupials

* * * * * * *


Other animals

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


External links


Kinsey Institute on the penis
{{Authority control Animal male reproductive system Articles containing video clips Sex organs