The menstrual flow results due to breakdown of...........

Answer

**Step-by-Step Solution:**

1. **Understanding Menstrual Flow**: Menstrual flow refers to the shedding of the uterine lining that occurs when fertilization does not take place. This is a part of the menstrual cycle in females.

2. **Role of the Uterine Lining**: The uterine lining, known as the endometrium, thickens in preparation for a potential pregnancy. If fertilization does not occur, this lining is no longer needed.

3. **Hormonal Influence**: The maintenance of the endometrial lining is influenced by hormones, particularly progesterone. When pregnancy does not occur, progesterone levels drop.

4. **Breakdown of the Endometrium**: The decrease in progesterone leads to the breakdown of the endometrial lining. This breakdown is what causes the menstrual flow.

5. **Conclusion**: Therefore, the menstrual flow results from the breakdown of the endometrial lining of the uterus.

**Final Answer**: The menstrual flow results due to the breakdown of the endometrial lining of the uterus.

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