THE OVARIAN CYCLE • It lasts about 28 days. 1- Growth of the follicle: During 14 days. After this, ovulation occurs. The follicle moves to the ovary wall and realese the ovum in the Fallopian tube. 2- Formation of corpus luteum: The rest of the follicle become a mass of yellow cells (corpus luteum) that disintetegrates and a new cycle begins.THE UTERINE CYCLE AND MENSTRUATION • At the same time of the ovarian cycle. 1- Menstruation or period: The endometrium, which is very thick and vascularised (with a lot of capillaries) is shed and expelled through the vagina along with the blood contained in the capillaries. 2- Endometrium regrows: At about day 14 endometrium begins to regow. 3- Endometrium thickens and becomes vascularised: If the ovum is fertilised, the embryo develops there. If not, a new cycle begins (menstruation). THE HORMONAL REGULATION OF THE CYCLES • The ovarian and uterine cycles are regulated by hormones: – FSH: Secreted by the pituitary gland. • Stimulates the growth of a follicle. • Stimulates the production of oestrogens in the ovary. • Oestrogenes cause the endometrium to thicken and triggers the secretion of LH by the pituitary gland. – LH: Produces ovulation. – After ovulation, the corpus luteum secretes oestrogenes and progesterone which cause endometrium to thicken and inhibit the secretion of pituitary hormones (FSH, LH).