oogenesis /ō′əjen″əsis/ [Gk, oon + genesis, origin] , the formation of the female gametes, or ova. The female infant is born with the entire number of primary oocytes that will function throughout reproductive life. Only a fraction of these survive until puberty, and only a small percentage will be ovulated. Follicles containing the primary oocytes are found in varying stages of development in the ovary of the sexually mature woman. Egg and sperm formation differ considerably in the number and size of gametes resulting from gametogenesis, the total number of gametes produced in a lifetime, and the time sequence for the initiation of the meiotic divisions and the completion of the cycle. Also called ovogenesis. Compare spermatogenesis. See also gametogenesis, meiosis, menstrual cycle, ovulation. −oogenetic, adj.
