Which one of the following statements is incorrect about menstrual cycle ?

Options

A. The first menstruation begins at puberty and is called menarche
B. Lack of menstruation may also occur due to some environmental factors like stress, poor health
C. Corpus luteum secretes large amounts of progesterone which is essential for maintenance of endometrium
D. In absence of fertilisation, corpus luteum degenerates in luteal phase and new follicles start developing immediately

Explanation

To determine which statement is incorrect about the menstrual cycle, let's analyze each option step by step.

### Step-by-Step Solution:

1. **Option 1: The first menstruation begins at puberty and is called menarche.**
- Menarche is indeed the term used to describe the first occurrence of menstruation, which typically happens during puberty.
- **Conclusion:** This statement is correct.

2. **Option 2: Lack of menstruation may occur due to some environmental factors like stress and poor health.**
- It is true that lack of menstruation (amenorrhea) can be influenced by various factors, including stress, poor health, and other environmental conditions.
- **Conclusion:** This statement is correct.

3. **Option 3: Corpus luteum secretes large amounts of progesterone which is essential for maintenance of endometrium.**
- The corpus luteum, formed from the remnants of the follicle after ovulation, does secrete progesterone. This hormone is crucial for maintaining the endometrial lining in preparation for a potential pregnancy.
- **Conclusion:** This statement is correct.

4. **Option 4: In absence of fertilization, corpus luteum degenerates in luteal phase and new follicles start developing immediately.**
- In the luteal phase, if fertilization does not occur, the corpus luteum does degenerate. However, new follicle development does not begin immediately; the luteal phase must complete, followed by menstruation before new follicles start to develop.
- **Conclusion:** This statement is incorrect.

### Final Answer:
The incorrect statement about the menstrual cycle is **Option 4**: "In absence of fertilization, corpus luteum degenerates in luteal phase and new follicles start developing immediately."

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