Question

Explain the events (both hormonal and structural) that occur at the time of ovulation till the onset of the next menstrual cycle.

Answer 1

1. One ovum is released (ovulation) during the middle of each menstrual cycle. The major events of the menstrual cycle are shown in Figure. The cycle starts with the menstrual phase, when menstrual flow occurs, and it lasts for 3-5 days.
2. The menstrual flow results from the breakdown of the endometrial lining of the uterus and its blood vessels, which forms liquid that comes out through the vagina.
3. Menstruation only occurs if the released ovum is not fertilised. Lack of menstruation may be indicative of pregnancy. However, it may also be caused by some other underlying causes like stress, poor health, etc
4. The menstrual phase is followed by the follicular phase. During this phase, the primary follicles in the ovary grow to become a fully mature Graafian follicle, and simultaneously, the endometrium of the uterus regenerates through proliferation.
5. These changes in the ovary and the uterus are induced by changes in the levels of pituitary and ovarian hormones.