Monthly variations in hormone levels

•Follicular phase Days 1 to 13

•FSH and LH stimulate the dominant follicle to rapidly grow in size

•As antral follicle matures, its oocyte finishes meiosis I, resulting in a secondary oocyte and a polar body (each with 23 chromosomes)

•Ovulation Day 14

•A peak in LH causes mature follicle to release secondary oocyte

•Luteal phase Days 15 to 28

•Granulosa cells of former follicle become corpus luteum

•Secretes progesterone and estrogen for possible pregnancy

•As corpus luteum degenerates (if no fertilization occurs), it’s release of estrogen/progesterone decreases, resulting in menstruation (menses or period); first menstruation is called menarche

Learn: Ch28 reproductive