In a average menstrual cycle of 28 days , which of these events is correctly matched with the time of its occurrence ?

Options

A. Release of ovum : `5^(th)` day
B. Endometrium degenerates : `5^(th) -10^(th)` day
C. Endometrium secretes nutrients for implantation : `15^(th)-28^(th)` day
D. Rise in progesterone level : `1^(st) -15^(th)` day

Answer

To solve the question regarding the average menstrual cycle of 28 days and identify which event is correctly matched with its time of occurrence, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Menstrual Cycle**: The average menstrual cycle lasts about 28 days and can be divided into two main phases: the follicular phase (first half) and the luteal phase (second half).

2. **Identifying Key Events**:
- **Days 1-5**: Menstrual bleeding occurs as the endometrial lining sheds if there is no pregnancy.
- **Days 6-14**: The endometrium begins to thicken and proliferate in preparation for potential implantation. This is also when the follicles in the ovaries mature.
- **Day 14**: Ovulation occurs, where the mature ovum is released from the ovary.
- **Days 15-28**: The luteal phase begins. The corpus luteum forms from the remnants of the follicle and secretes progesterone, which helps maintain the endometrial lining for possible implantation.

3. **Reviewing the Options**: We need to analyze the provided options to see which one correctly matches an event with its timing:
- **Option A**: Ovum is released on the 5th day. (Incorrect, as ovulation occurs around day 14)
- **Option B**: Endometrium degenerates from the 5th to 10th day. (Incorrect, as the endometrium proliferates during this time)
- **Option C**: Endometrium secretes nutrients for implantation from the 15th to 28th day. (Correct, as this is when the endometrium prepares for potential implantation)
- **Option D**: Progesterone levels increase from the 1st to 15th day. (Incorrect, as progesterone levels rise after ovulation, primarily during the luteal phase)

4. **Conclusion**: Based on the analysis, the correct answer is **Option C**, which states that the endometrium secretes nutrients for implantation from the 15th to 28th day.