Penis

A penis (/ˈpiːnɪs/; pl.: penises or penes) is a male sex organ that is used to inseminate female or hermaphrodite animals during copulation.^[1][2] Such organs occur in both vertebrates and invertebrates, including humans, but not in all male animals.

It has been suggested that Human penis be merged into this article. (Discuss) Proposed since November 2024.

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Penis
Penis of an Asian elephant
Details
Precursor	Genital tubercle (amniotes)
System	Reproductive system, sometimes with the genitourinary system
Identifiers
Latin	penis
Anatomical terminology [edit on Wikidata]

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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.

The word "penis" is taken from the Latin word for "tail". Some derive that from Indo-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". The Oxford English Dictionary cites an example of the word yard used in this sense from 1379,^[3] and notes that in his Physical Dictionary of 1684, Steven Blankaart defined the word penis as "the Yard, made up of two nervous Bodies, the Channel, Nut, Skin, and Fore-skin, etc."^[4] According to 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 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" (from Greek φαλλος) is sometimes used to describe the penis, although "phallus" originally was used to describe representations, pictorial or carved, of the penis.^[5]

A tiger's penis is aimed backward during urination. Tigers scent-mark their territories with pheromones in urine.^[7]

The external genital organs appeared in the Devonian, about 410 million years ago, when tetrapods 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 to internal fertilization.

Among amniotes, the development of an erectile penis occurred independently for mammals, squamates (lizards and snakes), testudines (turtles), and archosaurs (crocodiles and birds).

Over time, birds have lost this organ, with the exception of Paleognathae and Anseriformes.^[9]

The penis is an intromittent organ used to transfer sperm into the female genital tract (i.e., vagina or cloaca) for potential fertilization and, in the case of placentals, also for the excretion of urine.^[10][11] The penises of different animal groups are not homologous with each other, but were created several times independently of each other in the course of evolution.

An erection is the stiffening and rising of the penis, which occurs during sexual arousal, though it can also happen in non-sexual situations. During ejaculation, a series of muscular contractions delivers semen, containing male gametes known as sperm cells or spermatozoa, from the penis. Ejaculation is usually accompanied by orgasm.

The last common ancestor of all living amniotes (mammals, birds and reptiles) likely possessed a penis.^[12]

Harvestmen are the only male arachnids that have a penis.

In male insects, the structure analogous to a penis is known as an aedeagus. The male copulatory organ of various lower invertebrate animals is often called the cirrus.^[33]

In 2010, entomologist Charles Linehard described a new genus of barkflies called Neotrogla. 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 related Afrotrogla.^[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 in heraldry, where the adjective pizzled (or vilené^[41]) indicates that part of an animate charge's anatomy, especially if coloured differently.