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Oogenesis, ovogenesis, or oögenesis 〔(Merriam-Webster Online Dictionary Definition: Oogenesis )〕 is the creation of an ovum (egg cell). It is the female form of gametogenesis; the male equivalent is spermatogenesis. It involves the development of the various stages of the immature ovum. ==Oogenesis in mammals== In mammals, the first part of oogenesis starts in the germinal epithelium, which gives rise to the development of ovarian follicles, the functional unit of the ovary. Oogenesis consists of several sub-processes: oocytogenesis, ootidogenesis, and finally maturation to form an ovum (oogenesis proper). Folliculogenesis is a separate sub-process that accompanies and supports all three oogenetic sub-processes. Oogonium —(Oocytogenesis)—> Primary Oocyte —(Meiosis I)—> First Polar Body (Discarded afterward) + Secondary oocyte —(Meiosis II)—> Second Polar Body (Discarded afterward) + Ovum It should be noted that oocyte meiosis, important to all animal life cycles yet unlike all other instances of animal cell division, occurs completely without the aid of spindle-coordinating centrosomes.〔Szollosi D, Calarco P, Donahue RP (1972). Absence of centrioles in the first and second meiotic spindles of mouse oocytes. ''J Cell Sci'' 11(2):521-541. PMID 5076360〕〔Manandhar G, Schatten H, Sutovsky P(2005). Centrosome reduction during gametogenesis and its significance. Biol Reprod 72(1):2-13. Review. PMID 15385423〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「oogenesis」の詳細全文を読む スポンサード リンク
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