In simplest type of placenta, Six barriers separate maternal blood from foetal blood. How many barriers are lost in human placenta?

Options

A. One Y-chromosome
B. Two haploid nuclei fuse but the fusion nucleus divides immediately to form two haploid nuclei.
C. three
D. four

Answer

To solve the question regarding the number of barriers lost in the human placenta compared to the simplest type of placenta, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Basic Concept of Placental Barriers**:
- In the simplest type of placenta, there are six barriers that separate maternal blood from fetal blood. These barriers are crucial for the exchange of nutrients and waste products between the mother and fetus.

2. **Identify the Components of the Placental Barriers**:
- The six barriers typically consist of:
- Maternal endothelium
- Maternal connective tissue
- Uterine epithelium
- Trophoblast cells
- Fetal connective tissue
- Fetal endothelium

3. **Analyze the Structure of the Human Placenta**:
- In the human placenta, the structure is modified, and it consists of three main layers:
- Trophoblastic epithelium
- Chorionic connective tissue
- Fetal capillary endothelium

4. **Calculate the Number of Barriers Lost**:
- Since the human placenta has three layers remaining from the original six, we can determine how many barriers have been lost:
- Total barriers in simplest placenta: 6
- Barriers remaining in human placenta: 3
- Barriers lost = Total barriers - Barriers remaining = 6 - 3 = 3

5. **Conclusion**:
- Therefore, the number of barriers lost in the human placenta is **3**.

### Final Answer:
The number of barriers lost in the human placenta is **3**.