Q19. Explain the phases of menstrual cycle.

Answer:

A. Menstrual Phase:
During this phase soft tissue of endometrial lining of the uterus disintegrates causing bleeding. The underutilized egg and soft tissues are discharged. It lasts for 3-5 days.

B. Follicular Phase/Proliferative Phase:
The primary follicles in the ovary grow and become a fully mature Graafian follicle. The endometrium of the uterus is regenerated due to the secretion of LH and FSH from anterior pituitary and ovarian hormone, estrogen. It lasts for about 10 to 14 days.

C. Ovulatory Phase:
Rapid secretion of LH (LH surge) induces rupture of Graafian follicle, thereby leading to ovulation (release of ovum). It lasts for only about 48 hours.

D. Luteal Phase/Secretory Phase:
In this phase the ruptured follicle changes into corpus luteum in the ovary and it begins to secrete the hormone progesterone. The endometrium thickens further, and their glands secrete a fluid into the uterus. Estrogen and progesterone levels rise during this phase. It lasts for only 1 day.

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