- Oogonium
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Oogonium Gray's subject #3 38 MeSH Oogonia "Oogonium" (plural oogonia) may refer to either a primordial oocyte in a female fetus or the female gametangium of certain thallophytes.
Contents
in the fetus
Main article: OogenesisOogonia are formed in large numbers by mitosis early in fetal development from primordial germ cells. In humans they start to develop between weeks 4 and 8 and are present in the fetus between weeks 5 and 30. Once the primordial germ cells have arrived in the ovary, they develop into oogonia. Oogonia migrate from the yolk sac to the genital ridge (site of the future ovaries) 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 oocytes; 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 in human females.
in thallophytes
In phycology and mycology, oogonium refers to a female gametangium if the union of the male (motile or non-motile) and the female gamete takes place within this structure.[1][2] Oogonia are usually rounded cells or sacs containing one or more oospheres. The male (antheridium) usually produces many cells with flagella except in the Rhodophyta which have no flagella.[3]
References
- ^ 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
- ^ Smyth, G.M. 1955. Cryptogamic Botany. vol. 1. McGraw-Hill Book Company
- ^ Fritsch, F.E. 1965. The Structure and Reproduction of the Algae. Vol. 1 Cambridge University Press
External links
Categories:- Germ cells
- Cell biology stubs
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