Explain the various phases of the menstrual cycle.

Explanation

Menstrual cycle comprses of the following phases
1. Menstrual phase
2. Follicular or proliferative phase
3. Ovulatory phase
4. Luteal or secretory phase
1. Menstrual phase :
(i) The cycle starts with the menstrual phase when menstrual flow occurs and lasts for 3-5 days.
(ii) Menstruation occurs only if the released ovum is not fertilized.
2. Follicular or proliferative phase:
(i) The follicular phase extends from the 5th day of the cycle until the time of ovulation.
It stimulates follicular development and secretion of oestrogen by the follicle cells.
3. Ovulatory phase :
(i) Both LH and FSH attain peak level in the middle of the cycle (about the 14th day.)
(ii) Maximum secretion of LH during the mid cycle called LH surge induces the rupture of the Graffian follicle peritoneal cavity. This process is called as ovulation.
4. Luteal or secretory phase :
(i) During luteal phase, the ramaining part of the Graafian follicle is transformed into a transitory endocrine gland called corpus luteum.
(ii) The corpus luteum secretes large amount of progesterone which is essential for the maintenance of the endometrium.
(iii) During pregnancy all events of menstual cycle stop and there is no menstruation.