oogenesis
n. the process by which germ cells divide and differentiate to produce female gametes (ova). In human females, primary oocytes are formed in the ovary during embryonic development by the proliferation and differentiation of precursor cells called oogonia (sing.
oogonium). The primary oocytes enter into the first division of meiosis but then remain suspended at this stage of cell division until puberty. Thereafter, roughly once a month until menopause, one primary oocyte resumes meiosis and completes the first meiotic division to produce two unequally sized daughter cells: The larger one is the secondary oocyte, and the smaller is a polar body. Following ovulation, the secondary oocyte undergoes the second meiotic division to produce an ovum and another polar body. The first polar body might also divide to produce two tiny cells, resulting in three polar bodies, which are normally nonfunctional and degenerate.