The word "penis" is taken from theLatin word for "tail". Some derive that fromIndo-European*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". TheOxford English Dictionary cites an example of the wordyard used in this sense from 1379,[4] and notes that in hisPhysical Dictionary of 1684,Steven Blankaart defined the wordpenis as "the Yard, made up of two nervous Bodies, the Channel, Nut, Skin, and Fore-skin, etc."[5] According toWiktionary, this term meant (among other senses) "rod" or "bar".
As with nearly any aspect of the body involved in sexual orexcretory functions, the penis is the subject of manyslang words andeuphemisms for it, a particularly common and enduring one being "cock". SeeWikiSaurus:penis for a list of alternative words for penis.
The Latin word"phallus" (fromGreek φαλλος) is sometimes used to describe the penis, although "phallus" originally was used to describerepresentations, pictorial or carved, of the penis.[6]
The external genital organs appeared in theDevonian, about 410 million years ago, whentetrapods began to abandon the aquatic environment.[8] In fact, the necessity to overcome the absence of a liquid phase in which to release the gametes was achieved through the transition tointernal fertilization.
The penis is anintromittent organ used to transfersperm into the femalegenital tract (i.e.,vagina orcloaca) for potentialfertilization. The penises of different animal groups are nothomologous with each other, but were created several times independently of each other in the course of evolution.
Anerection is the stiffening and rising of the penis, which occurs duringsexual arousal, though it can also happen in non-sexual situations.Duringejaculation, a series of muscular contractions deliverssemen, containing malegametes known as sperm cells orspermatozoa, from the penis. Ejaculation is usually accompanied byorgasm.
The last common ancestor of all livingamniotes (mammals, birds and reptiles) likely possessed a penis.[10]
Vertebrates
Birds
Maleducks have a corkscrew-shaped penis to match the females' corkscrew vaginas. This favors fertilization by fitter mates over unwanted aggressors.[11]
Most male birds (e.g.,roosters andturkeys) have acloaca (also present on the female), but not a penis. Among bird species with a penis arepaleognaths (tinamous andratites)[12] andAnatidae (ducks, geese and swans).[13] Themagpie goose in the familyAnseranatidae also has a penis. A bird penis is different in structure from mammal penises, being an erectile expansion of the cloacal wall (in ducks) and being erected bylymph, not blood.[14] It is usually partially feathered and in some species features spines and brush-like filaments, and in a flaccid state, curls up inside the cloaca.
As with any other bodily attribute, the length and girth of the penis can be highly variable betweenmammals of differentspecies.[15][16] In many mammals, the penis is retracted into aprepuce when not erect. Mammals have eithermusculocavernous penises, which expand while erect, orfibroelastic penises, which become erect by straightening without expanding.[17]Preputial glands are present in some prepuces. Inplacentals, theurethra, which is connected to thevasa deferentia, travels through and exits the penis, thus bothurine and semen are expelled from this organ.[18][19] Theperineum oftesticond mammals (mammals without ascrotum) separates theanus and the penis.
A bone called thebaculum is present in most placentals but absent in humans, cattle and horses.
In mammals, the penis is divided into three parts:[20]
In maleinsects, the structure analogous to a penis is known as anaedeagus. The male copulatory organ of various lower invertebrate animals is often called thecirrus.[33]
In 2010, entomologist Charles Linehard described a new genus ofbarkflies calledNeotrogla. 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.[34] A similar female structure has also been described in the closely relatedAfrotrogla.[35] Scientists who study these insects have occasionally called the gynosome a "female penis"[36][37] and insisted to drop the definition of penis as "the male copulatory organ".[38] Motivations for using the term "female penis" include that such a term "is easier to understand and much more eye-catching"[39] and that the gynosome have "analogous features" with male penises.[38] Meanwhile, critics have argued that it does not fit the intromittent organ definition of "a structure that enters the female genital tract and deposits sperm".[40]
Pizzles are represented inheraldry, where the adjectivepizzled (orvilené[41]) indicates that part of an animatecharge's anatomy, especially if coloured differently.
^Armati, Patricia J.; Dickman, Chris R.; Hume, Ian D. (2006-08-17).Marsupials. Cambridge University Press.ISBN978-1-139-45742-2.
^Gadow, H. On the systematic position of Notoryctes typhlops. Proc. Zool. Soc. London 1892, 361–370 (1892).
^Riedelsheimer, B., Unterberger, P., Künzle, H. and U. Welsch. 2007. Histological study of the cloacal region and associated structures in the hedgehog tenrec Echinops telfairi. Mammalian Biology 72(6): 330-341.
^Lutz, Dick (2005), Tuatara: A Living Fossil, Salem, Oregon: DIMI PRESS,ISBN0-931625-43-2
^Yoshizawa K, Ferreira R.L., Yao I, Lienhard C & Kamimura Y. "Independent origins of female penis and its coevolution with male vagina in cave insects (Psocodea: Prionoglarididae)".Biology Letters14(11):doi.org/10.1098/rsbl.2018.0533
^Yoshizawa K, Ferreira R.L., Lienhard C & Kamimura Y. (2019). "Why Did a Female Penis Evolve in a Small Group of Cave Insects?".BioEssays41(6):doi.org/10.1002/bies.201900005
^Hayssen V. (2020). "Misconceptions about Conception and Other Fallacies: Historical Bias in Reproductive Biology".Integrative and Comparative Biology60(3): p. 683-791:doi.org/10.1093/icb/icaa035
Bates, Paul J. J.; Ratrimomanarivo, Fanja H.; Harrison, David L.; Goodman, Steven M. (December 2006). "A description of a new species of Pipistrellus (Chiroptera: Vespertilionidae) from Madagascar with a review of related Vespertilioninae from the island".Acta Chiropterologica.8 (2):299–324.doi:10.3161/1733-5329(2006)8[299:ADOANS]2.0.CO;2.S2CID85825521.
![A tiger's penis is aimed backward during urination. Tigers scent-mark their territories with pheromones in urine.[7]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aTiger_Tadoba_NP.jpg)
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