Oogonium
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Name = Oogonium |
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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]]