surrounded by a layer of cells (granulosa cells). primordial follicle. all primary oocytes enters meiosis I and stall. then birth of girl.
2 million primary oocyte
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.
in mature follicle. stalls midway of meiosis II. contains zona pellucida, corona radiata which protect it. is released from mature follicle at ovulation.
several layers of granulosa cells.
oocyte is viable for 12-24 hours if no sperm present. ruptured follicle converts into corpus luteum.