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{{Short description|Biological part involved in sexual reproduction}}
{{pp|small=yes}} 
{{Use dmy dates|date=September 2020}}

[[File:CharaV3.jpg|thumb|The sex organs of the [[green algae]] ''[[Chara (alga)|Chara]]'' are the male [[Antheridium|antheridia]] (red) and female [[Archegonium|archegonia]] (brown)]]
A '''sex organ''', also known as a '''reproductive organ''', is a part of an [[organism]] that is involved in [[sexual reproduction]]. Sex organs constitute the primary [[sex characteristics]] of an organism. Sex organs are responsible for producing and transporting [[gametes]], as well as facilitating [[fertilization]] and supporting the development and [[birth]] of offspring. Sex organs are found in many species of animals and plants, with their features varying depending on the species.

Sex organs are typically differentiated into [[male]] and [[female]] types. 

In animals (including humans), the male sex organs include the [[testicle]]s, [[epididymis|epididymides]], and [[penis]]; the female sex organs include the [[clitoris]],  [[Ovary|ovaries]], [[oviduct]]s, and [[vagina]]. The testicle in the male and the ovary in the female are called the ''primary sex organs''.<ref name="Clark">{{cite book|last=Clark|first=Robert K.|title=Anatomy and Physiology: Understanding the Human Body|url=https://books.google.com/books?id=4idMNpe04qgC&q=primary+sex+organ&pg=PA268|publisher=Jones & Bartlett Learning|page=25|language=en|date=2005|isbn=9780763748166}}</ref> All other sex-related organs are known as ''secondary sex organs''. The outer parts are known as the '''genitals''' or '''external genitalia''', visible at birth in both sexes,<ref name="Clark"/> while the inner parts are referred to as '''internal genitalia''', which in both sexes, are always hidden.<ref>{{cite book|last=Deol|first=Pooja Soni|title=ANATOMY PHYSIOLOGY OF FEMALE REPRODUCTIVE SYSTEM|url=https://books.google.com/books?id=gO7aEAAAQBAJ&pg=PA14|publisher=Blue Rose Publishers|page=14|date=2023}}</ref>

In plants, male reproductive structures include [[stamens]] in flowering plants, which produce [[pollen]].<ref>{{Cite web |title=Parts of a Flower |url=https://www.amnh.org/learn-teach/curriculum-collections/biodiversity-counts/plant-identification/plant-morphology/parts-of-a-flower |website=[[American Museum of Natural History]] |access-date=19 March 2023 |archive-date=19 March 2023 |archive-url=https://web.archive.org/web/20230319032014/https://www.amnh.org/learn-teach/curriculum-collections/biodiversity-counts/plant-identification/plant-morphology/parts-of-a-flower |url-status=live }}</ref> Female reproductive structures, such as [[pistils]] in flowering plants, produce [[ovules]] and receive pollen for fertilization.<ref name=EB1911>{{cite EB1911 |wstitle=Pollination |volume=22 |pages=2–5}}</ref> [[Moss]]es, [[fern]]s, and some similar plants have [[gametangia]] for reproductive organs, which are part of the [[gametophyte]].<ref>{{cite web |url=http://biology.clc.uc.edu/courses/Bio106/mosses.htm |title=Mosses and Ferns |publisher=Biology.clc.uc.edu |date=2001-03-16 |access-date=2012-08-01 |url-status=dead |archive-url=https://web.archive.org/web/20120728014926/http://biology.clc.uc.edu/courses/Bio106/mosses.htm |archive-date=28 July 2012}}</ref> The [[flower]]s of [[flowering plant]]s produce pollen and [[egg cell]]s, but the sex organs themselves are inside the gametophytes within the pollen and the ovule.<ref>{{cite web |date=2010-05-18 |title=Flowering Plant Reproduction |url=http://www2.estrellamountain.edu/faculty/farabee/BIOBK/BioBookflowers.html |archive-url=https://web.archive.org/web/20121008233734/http://www2.estrellamountain.edu/faculty/farabee/BIOBK/BioBookflowers.html |archive-date=Oct 8, 2012 |access-date=2012-08-01 |publisher=Emc.maricopa.edu}}</ref> [[Conifer|Coniferous plants]] likewise produce their sexually reproductive structures within the gametophytes contained within the [[Conifer cone|cones]] and pollen. The cones and pollen are not themselves sexual organs.

Together, the sex organs constitute an organism's [[reproductive system]].<ref name=EB1911-2>{{cite EB1911 |wstitle=Reproductive System |volume=23}}</ref>

== Terminology ==
{{One source section
| date = August 2021
}}
The ''primary sex organs'' are the [[gonad]]s, a pair of internal sex organs, which diverge into [[testicle]]s following male development or into [[Ovary|ovaries]] following female development.<ref>{{Cite encyclopaedia |title=Gonad |url=https://www.britannica.com/science/gonad |access-date=2024-08-21 |encyclopaedia=Encyclopædia Britannica |language=en}}</ref> As primary sex organs, gonads generate reproductive [[gamete]]s containing inheritable [[DNA]]. They also produce most of the primary hormones that affect sexual development, and regulate other sexual organs and sexually differentiated behaviors.

''Secondary sex organs'' are the rest of the reproductive system, whether internal or external. The [[Latin]] term ''genitalia'', sometimes anglicized as ''genitals'', is used to describe the externally visible sex organs.

In general [[zoology]], given the great variety in organs, physiologies, and behaviors involved in [[copulation (zoology)|copulation]], male genitalia are more strictly defined as "all male structures that are inserted in the female or that hold her near her [[gonopore]] during sperm transfer"; female genitalia are defined as "those parts of the female reproductive tract that make direct contact with male genitalia or male products (sperm, [[spermatophores]]) during or immediately after copulation".<ref>Eberhard, W.G., 1985. Sexual Selection and Animal Genitalia. Harvard University Press</ref>{{Page needed|date=August 2021}}

== Evolution ==
{{Main|Evolution of sexual reproduction}}

It is hard to find a common origin for [[gonad]]s. However, gonads most likely evolved independently several times.<ref>{{Cite book|last=Schmidt-Rhaesa|first=Andreas|url=https://books.google.com/books?id=iiwTDAAAQBAJ|title=The Evolution of Organ Systems|date=2007-08-30|publisher=Oxford University Press|isbn=978-0-19-856668-7|pages=252|language=en}}</ref> At first, [[Testicle|testes]] and [[Ovary|ovaries]] evolved due to [[natural selection]].<ref>{{Cite book|last1=switze|first1=International Conference on Comparative Physiology 1992 Crans|url=https://books.google.com/books?id=zunYrumtsR8C&q=evolution+of+sex+differences|title=The Differences Between the Sexes|last2=Bassau|first2=Short &|date=1994-08-04|publisher=Cambridge University Press|isbn=978-0-521-44878-9|pages=54|language=en}}</ref>

A consensus has emerged that [[sexual selection]] represents a primary factor for genital evolution.<ref>{{Cite journal|last1=Langerhans|first1=R. Brian|last2=Anderson|first2=Christopher M.|last3=Heinen-Kay|first3=Justa L.|date=2016-09-06|title=Causes and Consequences of Genital Evolution|journal=Integrative and Comparative Biology|volume=56|issue=4|pages=741–751|doi=10.1093/icb/icw101|pmid=27600556|issn=1540-7063|doi-access=free}}</ref> Male genitalia show traits of [[divergent evolution]] that are driven by sexual selection.<ref>{{Cite journal|last=Simmons|first=Leigh W.|date=2014|title=Sexual selection and genital evolution|journal=Austral Entomology|language=en|volume=53|issue=1|pages=1–17|doi=10.1111/aen.12053|s2cid=53690631|issn=2052-1758|doi-access=free}}</ref>

== 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.

== Plants ==
{{main article|Alternation of generations|Plant reproductive morphology}}
In most plant species, an individual has both male and female sex organs (a [[hermaphrodite]]).<ref>{{Cite book|last1=Purves|first1=William K.|url=https://books.google.com/books?id=kS-h84pMJw4C&q=plant+sex+organs|title=Life: The Science of Biology|last2=Sadava|first2=David E.|last3=Orians|first3=Gordon H.|last4=Heller|first4=H. Craig|date=2001|publisher=Macmillan|isbn=978-0-7167-3873-2|pages=176|language=en}}</ref>

The [[Biological life cycle|life cycle]] of [[land plant]]s involves [[alternation of generations]] between a [[sporophyte]] and a [[haploid]] gametophyte.<ref>{{Cite book |last=Pal |first=Nishant |url=https://books.google.com/books?id=Y-_czgEACAAJ |title=Plant Biology |date=2021-12-06 |publisher=Independently Published |isbn=979-8-7799-0473-5 |language=en |access-date=25 March 2023 |archive-date=10 April 2023 |archive-url=https://web.archive.org/web/20230410180903/https://books.google.com/books?id=Y-_czgEACAAJ |url-status=live }}</ref> The [[gametophyte]] produces sperm or egg cells by [[mitosis]]. The sporophyte produces spores by [[meiosis]], which in turn develop into gametophytes. Any sex organs that are produced by the plant will develop on the gametophyte. The [[seed plant]]s, which include [[conifer]]s and [[flowering plant]]s, have small gametophytes that develop inside the pollen grains (male) and the [[ovule]] (female).

=== Flowers ===
In flowering plants, the [[flower]]s contain the sex organs.<ref>{{Cite book|last1=Purves|first1=William K.|url=https://books.google.com/books?id=kS-h84pMJw4C&q=plant+sex+organs|title=Life: The Science of Biology|last2=Sadava|first2=David E.|last3=Orians|first3=Gordon H.|last4=Heller|first4=H. Craig|date=2001|publisher=Macmillan|isbn=978-0-7167-3873-2|pages=665|language=en}}</ref>

Sexual reproduction in [[flowering plant]]s involves the union of the male and female germ cells, sperm and egg cells respectively. Pollen is produced in [[stamen]]s and is carried to the [[pistil]] or [[carpel]], which has the ovule at its base where [[fertilization]] can take place. Within each pollen grain is a male gametophyte, which consists of only three cells. In most flowering plants, the female gametophyte within the ovule consists of only seven cells. Thus there are no sex organs as such.

== Fungi ==
{{Main|Mating in fungi}}
The sex organs in [[Fungus|fungi]] are known as [[Gametangium|gametangia]]. In some fungi, the organs are indistinguishable from each other but, in other cases, male and female sex organs are clearly different.<ref>{{Cite book|last1=Heritage|first1=J.|url=https://books.google.com/books?id=C0Q0ApyDFzcC&q=sex+organs+in+fungi&pg=PA19|title=Introductory Microbiology|last2=Evans|first2=E. G. V.|last3=Killington|first3=R. A.|date=1996-01-26|publisher=Cambridge University Press|isbn=978-0-521-44977-9|pages=19|language=en}}</ref>

Similar gametangia that are similar are known as isogametangia. While male and female gametangia are known as heterogametangia, which occurs in the majority of fungi.<ref>{{Cite book|last1=Manoharachary|first1=C.|url=https://books.google.com/books?id=Neg4DwAAQBAJ&q=female+sex+organs+in+fungi&pg=PA328|title=Mycology and Microbiology (A Textbook for UG and PG Courses)|last2=Tilak|first2=K. V. B. R.|last3=Mallaiah|first3=K. V.|last4=Kunwar|first4=I. K.|date=2016-05-01|publisher=Scientific Publishers|isbn=978-93-86102-13-3|pages=328|language=en}}</ref>

== See also ==
{{Div col}}
* [[Andrology]]
* [[Emasculation]]
* [[Genital modification and mutilation]]
* [[Human sexuality]]
* [[Hysterectomy]]
* [[Intimate part]]
* [[Obstetrics and gynaecology]]
* [[Oophorectomy]]
* [[Orchiectomy]]
{{Div col end}}

== References ==
{{Reflist}}

==Further reading==
{{Commons category|Sexual anatomy}}
{{Wiktionary|Wikisaurus:genitalia}}
* {{cite book|last1=Leonard|first1=Janet L.|first2=Alex|last2=Córdoba-Aguilar|title=The Evolution of Primary Sexual Characters in Animals|year=2010|publisher=Oxford University Press|location=Oxford|isbn=978-0199717033|url=https://books.google.com/books?id=PgtXj5R6OfMC}}

{{Sex (biology)}}
{{human anatomical features}}
{{Authority control}}

[[Category:Sex organs| ]]