During _______________ the secretion of oestrogen stimulates the uterus for the thickening of the endometrium.

Options

A. Proliferative phase
B. Luteal phase
C. Menstrual phase
D. Ovulatory phase

Answer

**Step-by-Step Solution:**

1. **Identify the Context**: The question asks about a specific phase in the menstrual cycle where the secretion of estrogen leads to the thickening of the endometrium (the inner lining of the uterus).

2. **Understand the Menstrual Cycle Phases**: The menstrual cycle consists of several phases:
- Menstrual Phase
- Proliferative Phase
- Ovulatory Phase
- Luteal Phase

3. **Focus on the Proliferative Phase**:
- The proliferative phase occurs from the 1st to the 13th day of the menstrual cycle.
- During this phase, estrogen is the predominant hormone.
- Estrogen stimulates the thickening of the endometrium in preparation for a potential embryo.

4. **Eliminate Other Phases**:
- **Menstrual Phase**: This phase involves the shedding of the endometrium, not thickening.
- **Ovulatory Phase**: This phase is characterized by the release of the ovum and is dominated by LH (Luteinizing Hormone), not estrogen.
- **Luteal Phase**: In this phase, progesterone is the dominant hormone, and the focus is on maintaining the endometrium rather than thickening it.

5. **Conclusion**: Based on the information, the correct answer to fill in the blank is "proliferative phase".

**Final Answer**: During **proliferative phase**, the secretion of oestrogen stimulates the uterus for the thickening of the endometrium.

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