the procedure wherein germ cells separate and differentiate to generate female gametes. With regard to human females, primary oocytes are developed in the ovary during embryonic growth by the proliferation and distinguishing of precursor cells referred to as oogonia. The primary oocytes are introduce through the initial division of meiosis, but then remain inactive during this phase of cell division up till pubescence. Thereafter, approximately one time each month up till menopause, one primary oocyte restarts meiosis and finishes the initial meiotic separation to generate two differently-sized daughter cells: The bigger cell is the secondary oocyte, while at the same time the smaller cell is a polar body. Subsequent to ovulation, the secondary oocyte endures the second meiotic separation to generate an ovum and another polar body. The first polar body may additionally separate to generate two very minute cells, resulting in three polar bodies, that are generally non-actual and degenerate.
OOGENESIS: "Oogenesis does not occur in all mammals."