Editing Sex organ (section)

== Animals ==
===Vertebrates===
====Mammals====
{{anchor|Human genitals}}
{{Further|Mammalian reproductive system|Human reproductive system}}
The visible portion of [[eutheria]]n [[mammal]]ian genitals for males consists of the [[mammalian penis|penis]] and [[scrotum]]; for females, it consists of the [[vulva]].

Male [[placental mammals]] [[urination|urinate]] and [[ejaculation|ejaculate]] through one [[urinary meatus|urethral opening]] in the penis, while females have two separate [[Vaginal opening|vaginal]] and urethral openings.<ref name="Wake1992">{{cite book|author=Marvalee H. Wake|title=Hyman's Comparative Vertebrate Anatomy|url=https://books.google.com/books?id=VKlWjdOkiMwC&pg=PA583|year=1992|publisher=University of Chicago Press|isbn=978-0-226-87013-7|pages=583|author-link=Marvalee H. Wake}}</ref> Male and female genitals have many nerve endings, resulting in pleasurable and highly sensitive touch.<ref>{{cite book|author=Brigitta Olsen|title=Daphne's Dance: True Tales in the Evolution of Woman's Sexual Awareness|url=https://books.google.com/books?id=I9xrbK6CwzUC&pg=PA9|date=15 November 2009|publisher=Brigitta Olsen|isbn=978-0-9842117-0-8|page=9}}</ref> In most human societies, particularly in [[social conservatism|conservative]] ones, exposure of the genitals is considered a [[public indecency]].<ref>{{cite book|author=Anita Allen|title=Unpopular Privacy: What Must We Hide?|url=https://books.google.com/books?id=fxYhR6hqc3QC&pg=PA219|date=November 2011|publisher=Oxford University Press, US|isbn=978-0-19-514137-5|page=219}}</ref>

In humans, sex organs include:
{| class="wikitable"
|-
! [[Male]]
! [[Female]]
|-
|
'''External'''
* [[Human penis|Penis]]
** [[Foreskin]]
** [[Body of penis|Shaft]]
** [[Glans penis|Glans]]
* [[Scrotum]]
'''Internal'''
* [[Prostate]]
* [[Bulbourethral gland]]s
* [[Epididymis|Epididymides]]
* [[Vas deferens|Vasa deferentia]]
* [[Testicle]]s
* [[Seminal vesicles]]

[[File:ShortForeskin.jpg|thumb|center|Human male external sex organs (shaved [[pubic hair]])]]
|
'''External'''
* [[Vulva]]
** [[Clitoris]]
*** [[Clitoris#Glans|Glans]]
*** [[Clitoris#Body|Body]]
*** [[Clitoral hood|Hood]]
** [[Labia majora]]
** [[Labia minora]]
** [[Vulval vestibule|Vestibule]]
'''Internal'''
* [[Fallopian tube]]s
* [[Ovary|Ovaries]]
* [[Uterus]]
** [[Cervix]]
* [[Vagina]]
* [[Bartholin's gland]]s
* [[Skene's gland]]s

[[File:Vulva with tiny labia minora.jpg|thumb|upright|center|Human female external sex organs (shaved [[pubic hair]])]]
|}

===== Development =====
{{More citations needed section|date=August 2021}}{{Main article|Development of the reproductive system}}
{{See also|List of homologues of the human reproductive system}}
In typical [[prenatal development]], sex organs originate from a common [[primordium]] during early [[gestation]] and [[sexual differentiation|differentiate]] into male or female [[sex]]es. The [[SRY]] [[gene]], usually located on the [[Y chromosome]] and encoding the [[testis determining factor]], determines the direction of the differentiation. The absence of it allows the gonads to continue to develop into ovaries.

The development of the internal and external reproductive organs is determined by hormones produced by certain fetal gonads (ovaries or testicles) and the cells' response to them. The initial appearance of the [[fetus|fetal]] genitalia looks female-like: a pair of [[urogenital folds]] with a small protuberance in the middle, and the [[urethra]] behind the protuberance. If the fetus has testes and the testes produce testosterone, and if the cells of the genitals respond to the testosterone, the outer urogenital folds swell and fuse in the midline to produce the scrotum; the protuberance grows larger and straighter to form the penis; the inner urogenital swellings grow, wrap around the penis, and fuse in the midline to form the [[penile raphe]].<ref>{{cite book|last1=Hodges|first1=Frederick Mansfield S.|last2=Denniston|first2=George C.|last3=Milos|first3=Marilyn Fayre|publisher=Springer US|year= 2007|title=Male and Female Circumcision: Medical, Legal, and Ethical Considerations in Pediatric Practice|page=10|access-date=November 24, 2023|isbn=978-0-58539-937-9|url=https://books.google.com/books?id=U0EyBwAAQBAJ&pg=PA10&dq=}}</ref><ref>{{cite book|last1=Martin|first1=Richard J.|last2=Fanaroff|first2=Avory A.|last3=Walsh| first3=Michele C.|publisher=Elsevier Health Sciences|year=2014|title=Fanaroff and Martin's Neonatal-Perinatal Medicine E-Book: Diseases of the Fetus and Infant|page=1522|access-date=November 24, 2023|isbn=978-0-32329-537-6|url=https://books.google.com/books?id=AnVYBAAAQBAJ&pg=PA1522&dq=}}</ref> Each organ/body part in one sex has a [[homology (biology)|homologous]] counterpart.

The process of sexual differentiation includes the development of [[secondary sexual characteristics]], such as patterns of pubic and facial hair and female breasts that emerge at puberty.

{{anchor|Evolution}} Because of the strong [[sexual selection]] affecting the structure and function of genitalia, they form an organ system that evolves rapidly.<ref>Hosken, David J., and Paula Stockley."[http://www.sexologia.ulusofona.pt/biblio/Indice_files/Sexual%20selection%20and%20genital%20evolution.pdf Sexual selection and genital evolution]." {{Webarchive|url=https://web.archive.org/web/20171012045147/http://www.sexologia.ulusofona.pt/biblio/Indice_files/Sexual%20selection%20and%20genital%20evolution.pdf# |date=12 October 2017 }} Trends in Ecology & Evolution 19.2 (2004): 87-93.</ref><ref>Arnqvist, Göran. "[http://heart.sdsu.edu/~website/biology_307/pdfs/genitalia.pdf Comparative evidence for the evolution of genitalia by sexual selection]." {{Webarchive|url=https://web.archive.org/web/20120127135826/http://heart.sdsu.edu/~website/Biology_307/pdfs/genitalia.pdf# |date=27 January 2012 }} Nature 393.6687 (1998): 784.</ref><ref>Schilthuizen, M. 2014. [https://books.google.com/books?id=xqM7AgAAQBAJ&dq=nature%27s+nether+regions&pg=PT2 Nature's Nether Regions: What the Sex Lives of Bugs, Birds, and Beasts Tell Us About Evolution, Biodiversity, and Ourselves] {{Webarchive|url=https://web.archive.org/web/20230614234747/https://books.google.com/books?id=xqM7AgAAQBAJ&dq=nature%27s+nether+regions&pg=PT2 |date=14 June 2023 }}. Penguin USA</ref> A great variety of genital form and function may therefore be found among animals.

====Other animals====
In many other [[vertebrate]]s, a single posterior orifice (the [[cloaca]]) serves as the only opening for the reproductive, digestive, and urinary tracts (if present) in both sexes. All [[amphibian]]s, birds, [[reptile]]s,<ref>{{Cite web|date=2018|title=Male reproductive behaviour of Naja oxiana (Eichwald, 1831) in captivity, with a case of unilateral hemipenile prolapse|url=https://www.researchgate.net/publication/335270872}}</ref> some fish, and a few mammals ([[monotreme]]s, [[tenrec]]s, [[golden mole]]s, and [[marsupial mole]]s) have this orifice, from which they excrete both urine and feces in addition to serving reproductive functions.<ref>{{Cite web |title=Page:The Works of William Harvey (part 1 of 2).djvu/283 - Wikisource, the free online library |url=https://en.wikisource.org/wiki/Page:The_Works_of_William_Harvey_(part_1_of_2).djvu/283 |access-date=2023-03-25 |website=en.wikisource.org |language=en |archive-date=25 March 2023 |archive-url=https://web.archive.org/web/20230325152215/https://en.wikisource.org/wiki/Page:The_Works_of_William_Harvey_(part_1_of_2).djvu/283 |url-status=live }}</ref> Excretory systems with analogous purpose in certain invertebrates are also sometimes referred to as cloacae.

Penile and clitoral structures are present in some birds and many reptiles.

[[Sexing]] [[teleost]] fish is determined by the shape of a fleshy tube behind the anus known as [[genital papilla]].

===Invertebrates===
====Insects====
{{main|Insect reproductive system}}
[[File:Female genitalia Lepidoptera.jpg|thumb|right|The female [[Lepidoptera genitalia|genitalia of Lepidoptera]]]]
The organs concerned with [[insect]] mating and the deposition of eggs are known collectively as the external genitalia, although they may be largely internal; their components are very diverse in form.

====Slugs and snails====
{{main|Reproductive system of gastropods}}
The reproductive system of gastropods (slugs and snails) varies greatly from one group to another.

====Planaria====
{{main|Reproductive system of planarians}}
[[Planaria]] are flat worms widely used in biological research. There are sexual and asexual planaria. Sexual planaria are hermaphrodites, possessing both testicles and ovaries. Each planarian transports its excretion to the other planarian, giving and receiving sperm.