Trace FSH and LH control of follicles and ovulation, then interpret oestrogen/progesterone effects on the endometrium and cycle graphs in IB Biology SL D3.1.5.
Outline the role of hormones in the menstrual cycle.
FSH (released from pituitary) stimulates follicle growth (in ovary);
oocytes/egg cells mature;
cells of growing follicle produce estrogen;
estrogen signals endometrium/lining of uterus to thicken;
causes final maturation of follicle;
high levels of estrogen stimulate secretion of LH;
LH spike stimulates ovulation/follicle ruptures releasing oocyte/ova/egg cells;
LH stimulates follicle (left behind in ovary) to develop into corpus luteum;
LH stimulates corpus luteum to secrete progesterone/estrogen;
progesterone/estrogen stimulates continued development/maintenance of lining of uterus (in preparation for implantation of embryo);
if no pregnancy then corpus luteum disintegrates;
drop in progesterone/estrogen hormone levels causes breakdown in uterine lining/menstruation;
progesterone/estrogen inhibit FSH/LH release;