surrounded by a layer of cells (granulosa cells). primordial follicle. all primary oocytes enters meiosis I and stall. then birth of girl.
birth
2 million primary oocyte
puberty
50,000.
menstrual cycle
starts at puberty. 28 days, regulated by hormones. at beginning of each cycle a few primary oocytes continue to develop, usually only one finishes meiosis I. and becomes secondary oocyte and first polar body.
secondary oocyte
in mature follicle. stalls midway of meiosis II. contains zona pellucida, corona radiata which protect it. is released from mature follicle at ovulation.
zona pellucida
glycoproteins
corona radiata
several layers of granulosa cells.
after ovulation
oocyte is viable for 12-24 hours if no sperm present. ruptured follicle converts into corpus luteum.