Question

Explain various stages of the ovarian cycle.

Answer 1

The ovarian cycle is a sequence of changes in the ovary, usually occurring over about 28 days under the influence of pituitary and ovarian hormones.

1. Follicular phase (approximately days 1–14): FSH stimulates ovarian follicles to grow and one usually develops into a mature Graafian follicle. The developing follicle secretes oestrogen, which helps repair and thicken the uterine endometrium.
2. Ovulation (around day 14): A mid-cycle surge of LH, with a rise in FSH, causes the Graafian follicle to rupture and release a secondary oocyte.
3. Luteal phase (approximately days 14–28): Cells of the ruptured follicle form the corpus luteum, which secretes mainly progesterone. Progesterone maintains and further prepares the endometrium for implantation.
4. If fertilisation does not occur: The corpus luteum degenerates into the corpus albicans. Oestrogen and progesterone levels fall, and the endometrium breaks down, beginning menstruation.
5. If fertilisation occurs: The corpus luteum is maintained, progesterone remains high, and the menstrual cycle is suspended.