part_of part of part of only in taxon develops from Metazoa female reproductive system gonad ovary UMLS:C0029939 uberon XAO:0000258 gonada of female organism genitalia (...) while it is likely that Urbilateria lacked a complex somatic reproductive system, it is at present impossible to speculate on whether or not it possessed a true gonad, let alone any other somatic adaptations for reproduction (reference 1); Examination of different vertebrate species shows that the adult gonad is remarkably similar in its morphology across different phylogenetic classes. Surprisingly, however, the cellular and molecular programs employed to create similar organs are not evolutionarily conserved (reference 2).[uncertain][VHOG] ZFA:0000403 GAID:367 Female reproductive organ.[TAO] gonada of genitalia of female organism The gonad of a female organism which contains germ cells. female organism reproductive system gonad AAO:0000371 BTO:0000975 female organism reproductive system gonada FBbt:00004865 female reproductive system gonad female reproductive system gonada reproductive system of female organism gonada animal ovary BSA:0000080 gonada of female organism reproductive system EHDAA2:0001360 genitalia of female organism gonad female organism genitalia gonada BILA:0000125 ovarium gonad of female organism genitalia gonad of reproductive system of female organism ovarian female gonad EMAPA:17962 FMA:7209 EFO:0000973 MA:0000384 ovaries gonad of female reproductive system VHOG:0000251 gonad of female organism reproductive system TAO:0000403 gonada of female reproductive system ovum-producing ovary EV:0100111 NCIT:C12404 MESH:D010053 genitalia of female organism gonada female organism genitalia gonad UBERON:0000992 CALOHA:TS-0730 reproductive system of female organism gonad gonad of genitalia of female organism EHDAA:8124 Either of paired female reproductive organs involved in production of ova and female sex hormones.[AAO] gonada of reproductive system of female organism Ovaries of some kind are found in the female reproductive system of many animals that employ sexual reproduction, including invertebrates. However, they develop in a very different way in most invertebrates than they do in vertebrates, and are not truly homologous. 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, 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 monotremes, the egg is relatively large, filling the follicle, and distorting the shape of the ovary at maturity. Amphibians and reptiles have no ovarian medulla; the central part of the ovary is a hollow, lymph-filled space. The ovary of teleosts is also often hollow, but in this case, the eggs are shed into the cavity, which opens into the oviduct. Although most normal female vertebrates have two ovaries, this is not the case in all species. In birds and platypuses, the right ovary never matures, so that only the left is functional. In some elasmobranchs, the reverse is true, with only the right ovary fully developing. In the primitive jawless fish, and some teleosts, there is only one ovary, formed by the fusion of the paired organs in the embryo OpenCyc:Mx4rvVi9QJwpEbGdrcN5Y29ycA MIAA:0000125 female reproductive organ indifferent gonad