In a normal human female, why does menstruation only occurs if the released ovum is…

In a normal human female, why does menstruation only occurs if the released ovum is not fertilised? Explain.

Ans.

Menstruation occurs if the released ovum is not fertilized because:

When the released ovum is not fertilized:

1. The corpus luteum, formed from the ruptured follicle after ovulation, regresses.

2. Regression of the corpus luteum leads to a decrease in progesterone and estrogen levels.

3. Decreased hormone levels cause vasoconstriction of the spiral arteries in the endometrium.

4. Reduced blood flow to the endometrium results in ischemia and tissue necrosis.

5. The necrotic endometrial tissue sheds, leading to menstrual bleeding.

In summary, menstruation occurs due to the withdrawal of hormonal support and subsequent shedding of the uterine lining when the released ovum is not fertilized.