Oogonium 2395127 204232938 2008-04-08T15:38:00Z Kaobear 1739346 clean up using [[Project:AutoWikiBrowser|AWB]] {{Infobox Anatomy | Name = Oogonium | Latin = | GraySubject = 3 | GrayPage = 38 | Image = | Caption = | Image2 = | Caption2 = | System = | MeshName = Oogonia | MeshNumber = A05.360.490.690.700 | }} An '''oogonium''' (plural '''''oogonia''''') is an [[immature ovum]]. It is a female [[gametogonium]]. They are formed in large numbers by [[mitosis]] early in [[fetus|fetal]] life from [[germ cell|primordial germ cell]]s, which are present in the fetus between weeks 4 and 8. Oogonia are present in the fetus between weeks 5 and 30. Oogonia are also the female reproductive structures in certain [[thallophyte]]s, and are usually rounded [[cell (biology)|cell]]s or sacs containing one or more [[oosphere]]s. ==Further development== {{Main|Oogenesis}} Once the [[primordial germ cells]] have gotten to the [[ovary]], they develop into oogonia. During week 6 of development, oogonia migrate from the yolk sac to the genital ridge ( site of the future gonads-ovaries in this case) located on the posterior abdominal wall. Oogonia develop by [[mitosis]]. However, some of them become [[primary oocytes]], which begin [[meiosis]] which is halted in prophase I. When they have entered Prophase I of meiosis they become primary [[oocyte]]s; it is important to note that this process is complete before birth, in contrast to [[spermatogenesis]]. Primary oocytes are present from week 10 until menopause at ~53 years ==Oogamy== Oogamy may be spelt oögamy with a diaresis (or umlaut). The link with other articles may depend on this symbol. ==Oogonia== ===Algae=== This term is used in [[phycology]] (the study of algae) to refer to the union of the male (motile or non-motile) with the female [[gamete]].<ref name="Stegenga, Bolton and Anderson 97">'''Stegenga, H. Bolton, J.J. and Anderson, R.J.''' 1997. ''Seaweeds of the South African West Coast.'' Bolus Herbarium, University of Cape Tow. ISBN 0 7992 1793 X</ref>The female oogonium is usually enlarged and develops a single ovum. The male (''antheridium'') usually produces many cells with flagella except in the [[Rhodophyta]] which have no flagella. <ref name="Fitsch 65">'''Fritsch, F.E.''' 1965. ''The Structure and Reproduction of the Algae.'' Vol. '''1''' Cambridge University Press</ref> There is no evidence that the red algae ever had flagella, or cilia and it is suggested that they are the most primitive [[eukaryotes]].<ref name="Cole and Sheath 90">'''Cole, K.M. and Sheath, R.G.''' (Eds) 1990. ''Biology of Red Algae.'' Cambridge University Press. ISBN 0 521 34301 1</ref> ===Fungi=== Oogonia also occur in the [[fungi]].<ref name"Smyth 55">'''Smyth, G.M.''' 1955. ''Cryptogamic Botany.'' vol. 1. McGraw-Hill Book Company</ref> ==References== {{reflist}} ==External links== * [http://www.erin.utoronto.ca/~w3bio380/picts/lectures/lecture3/FollicleDev1.jpg Diagram at University of Toronto] [[Category:Germ cells]] {{Cell-biology-stub}} [[fr:Ovogonie]] [[id:Oogonium]] [[ja:卵原細胞]] [[pl:Lęgnia]] [[ru:Оогоний]]