Editing Ovary (section)

==Other animals==
[[File:Parasite140007-fig7 Philometra fasciati Moravec & Justine, 2008 (Nematoda, Philometridae).tif|thumb| Ovary of a marine fish and its parasite, the nematode ''[[Philometra]] fasciati'']]

Birds have only one functional ovary (the left), while the other remains vestigial. In mammals including humans, the female ovary is [[Homology (biology)|homologous]] to the male [[testicle]], in that they are both [[gonad]]s and [[endocrine gland]]s. Ovaries of some kind are found in the female reproductive system of many invertebrates  that employ [[sexual reproduction]]. However, they develop in a very different way in most invertebrates than they do in vertebrates, and are not truly homologous.<ref name=VB>{{cite book |author=Romer, Alfred Sherwood|author2=Parsons, Thomas S.|year=1977 |title=The Vertebrate Body |publisher=Holt-Saunders International |location= Philadelphia, PA|pages= 383–385|isbn= 978-0-03-910284-5}}</ref>

Many of the features found in human ovaries are common to all vertebrates, including the presence of follicular cells, tunica albuginea, and so on. However, many species produce a far greater number of eggs during their lifetime than do humans, so that, [[Fish_anatomy#Ovaries|in fish]] and amphibians, there may be hundreds, or even millions of fertile eggs present in the ovary at any given time. In these species, fresh eggs may be developing from the germinal epithelium throughout life. Corpora lutea are found only in mammals, and in some [[elasmobranch]] fish; in other species, the remnants of the follicle are quickly resorbed by the ovary. In birds, reptiles, and [[monotreme]]s, the egg is relatively large, filling the follicle, and distorting the shape of the ovary at maturity.<ref name=VB/>

Amphibians and reptiles have no ovarian medulla; the central part of the ovary is a hollow, [[lymph]]-filled space.<ref>{{Cite web | url=https://www.britannica.com/science/animal-reproductive-system/Accessory-glands | title=Animal reproductive system - Accessory glands}}</ref>

The ovary of [[teleost]]s is also often hollow, but in this case, the eggs are shed into the cavity, which opens into the [[oviduct]].<ref name=VB/> Certain [[nematode]]s of the genus ''[[Philometra]]'' are parasitic in the ovary of marine fishes and can be spectacular, with females as long as {{Cvt|40|cm}}, coiled in the ovary of a fish half this length.<ref name="MoravecJustine2014">{{cite journal|last1=Moravec|first1=František|last2=Justine|first2=Jean-Lou|title=Philometrids (Nematoda: Philometridae) in carangid and serranid fishes off New Caledonia, including three new species|journal=Parasite|volume=21|year=2014|pages=21|issn=1776-1042|doi=10.1051/parasite/2014022|pmid=24836940|pmc=4023622}} {{open access}}</ref> Although most female vertebrates have two ovaries, this is not the case in all species. In most birds and in [[platypus]]es, the right ovary never matures, so that only the left is functional. (Exceptions include the [[Kiwi (bird)|kiwi]] and some, but not all [[birds of prey|raptors]], in which both ovaries persist.<ref>{{cite journal | last1 = Fitzpatrick | first1 = F. L. | year = 1934 | title = Unilateral and bilateral ovaries in raptorial birds | journal = The Wilson Bulletin | volume = 46 | issue = 1| pages = 19–22 }}</ref><ref>{{cite journal | last1 = Kinsky | first1 = F. C. | year = 1971 | title = The consistent presence of paired ovaries in the Kiwi(Apteryx) with some discussion of this condition in other birds | journal = Journal of Ornithology | volume = 112 | issue = 3| pages = 334–357 | doi=10.1007/bf01640692| bibcode = 1971JOrni.112..334K | s2cid = 28261057 }}</ref>)  In some elasmobranchs, only the right ovary develops fully. In the primitive [[jawless fish]], and some teleosts, there is only one ovary, formed by the fusion of the paired organs in the embryo.<ref name="VB" />