The main cause of the disintegration of the endometrial lining

Options

A. LH surge
B. degeneration of corpus luteum
C. ovulation during mid-cycle
D. implantation leads to pregnancy

Answer

**Step-by-Step Solution:**

1. **Understanding the Endometrial Lining**: The endometrial lining is the inner layer of the uterus that thickens in preparation for a potential pregnancy. If pregnancy does not occur, this lining needs to disintegrate.

2. **Role of Hormones**: The maintenance and disintegration of the endometrial lining are primarily regulated by hormones, particularly progesterone. Progesterone is crucial for sustaining the endometrial lining after ovulation.

3. **Source of Progesterone**: Progesterone is secreted by the corpus luteum, which forms from the follicle after ovulation. This hormone helps maintain the endometrial lining, making it suitable for implantation of a fertilized egg.

4. **Degeneration of Corpus Luteum**: If fertilization does not occur, the corpus luteum degenerates. This degeneration leads to a decrease in progesterone levels in the body.

5. **Consequences of Low Progesterone**: The drop in progesterone levels causes the endometrial lining to disintegrate, leading to menstruation. Therefore, the main cause of the disintegration of the endometrial lining is the degeneration of the corpus luteum.

6. **Conclusion**: Based on the above points, the correct answer to the question is the second option: "degeneration of corpus luteum."

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