Oogenesis

Oogenesis is the creation of an ovum (egg cell) in the ovarian follicle of the ovary. Oogenesis is not to be confused with oocytogenesis, which is the formation of oocytes, which are the female gametocytes that divide later into ova.

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In mammals, oogonial transformation into oocytes (oocytogenesis) is completed either before or shortly after birth. The further development comes to a rest during prophase I of meiosis until puberty. In Ascaris, the oocyte does not even begin meiosis until the sperm touches it.

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In meiosis, the oocyte divides in four, of which only one becomes an ovum, the others becoming polar bodies. There may be two polar bodies, in which case one is diploid and did not undergo meiosis II.

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See also: spermatogenesis, folliculogenesis

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Ovum: An ovum (loosely, egg or egg cell) is a female sex cell or gamete. Both animals and seed plants have ova. The term ovule is used for the ovum of seed plants and for the young ovum of an animal....

Ovarian follicle: Ovarian follicles or Graafian follicles (after Regnier de Graaf) are the roughly spherical cell aggregations in the ovary containing an ovum and from which the egg is released during ovulation. It consists of an external fibro-vascular coat, an internal coat of nucleated cells, and a transparent, al...

Ovary: Ovaries are a part of a female organism that produces eggs....