Question

What is the role of hormones in the cyclic developments in the ovary and the uterus?

Answer 1

The cyclic changes in the ovary and uterus are coordinated by hypothalamic, pituitary and ovarian hormones.

1. GnRH from the hypothalamus stimulates the anterior pituitary to release FSH and LH.
2. FSH stimulates ovarian follicle growth. The developing follicles secrete oestrogen.
3. Oestrogen promotes repair and thickening of the endometrium during the proliferative phase. High mid-cycle hormone levels contribute to the LH surge.
4. LH triggers ovulation and stimulates formation of the corpus luteum.
5. Progesterone, secreted mainly by the corpus luteum, makes the endometrium thick, glandular and suitable for implantation. If fertilisation does not occur, the corpus luteum degenerates, hormone levels fall and menstruation begins.