If mammalian ovum fails to get fertilized, which of the following is unlikely ?

Options

A. Estrogen secretion further decreases
B. Progesterone secretion rapidly declines
C. Corpus luteum will disintegrate
D. Primary follicle starts developing

Answer

To answer the question "If mammalian ovum fails to get fertilized, which of the following is unlikely?", we can break down the biological processes that occur when fertilization does not happen.

### Step-by-Step Solution:

1. **Understanding Ovum and Fertilization**:
- The ovum (egg) is released from the ovary during ovulation. If it is not fertilized by sperm, it will not develop into a zygote.

2. **Disintegration of Corpus Luteum**:
- After ovulation, the ruptured follicle transforms into the corpus luteum, which secretes hormones (primarily progesterone and estrogen) to support the potential pregnancy.
- If fertilization does not occur, the corpus luteum disintegrates.

3. **Hormonal Changes**:
- The disintegration of the corpus luteum leads to a decrease in the levels of progesterone and estrogen.
- Progesterone is crucial for maintaining the endometrium (the uterine lining) for a potential pregnancy.

4. **Initiation of Menstrual Cycle**:
- The decrease in progesterone and estrogen results in the shedding of the endometrium, leading to menstruation. This marks the beginning of a new menstrual cycle.

5. **Development of Follicles**:
- In the absence of fertilization, the hormonal changes can lead to the development of new ovarian follicles. However, the question asks for something that is "unlikely" to happen.

6. **Identifying the Unlikely Event**:
- The development of primary follicles is a normal part of the ovarian cycle and can still occur even if fertilization does not happen. However, the question specifically asks for something that is unlikely to occur as a direct consequence of the ovum not being fertilized.

7. **Conclusion**:
- The correct answer is that the development of primary follicles is unlikely to be directly affected by the failure of fertilization. Thus, the option stating that "primary follicle starts developing" is the correct answer to the question.

### Final Answer:
The correct answer is that the development of primary follicles is unlikely to occur when the mammalian ovum fails to get fertilized.

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