Multicelluar, multinucleate, irregular mass of embryo which pass into uterine wall is

Options

A. Ectoderm
B. Endoderm
C. Syncytiotrophoblast
D. Amnion.

Answer

To solve the question regarding the multicellular, multinucleate, irregular mass of the embryo that passes into the uterine wall, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Terms**:
- The question describes a structure that is "multicellular" and "multinucleate." This suggests that it is made up of many cells and contains multiple nuclei within those cells.

2. **Identifying the Structure**:
- The term "irregular mass of embryo" indicates that we are looking for a specific part of the embryo that has a unique structure and function during implantation in the uterus.

3. **Function of the Structure**:
- The structure in question is involved in the process of implantation into the uterine wall. This process is crucial for establishing a connection between the embryo and the mother for nutrient exchange.

4. **Considering the Options**:
- The options provided are:
A) after the
B) end of the
C) syncytiotrophoblast
D) amnion
- Among these, "syncytiotrophoblast" is a term that refers to a specific layer of cells that forms during the early stages of embryonic development.

5. **Defining Syncytiotrophoblast**:
- The syncytiotrophoblast is a layer of tissue formed from the outer layer of the blastocyst. It is characterized by being multinucleate and plays a crucial role in invading the uterine wall to facilitate implantation and nutrient absorption from the mother.

6. **Conclusion**:
- Based on the characteristics and functions described, the correct answer to the question is **C) syncytiotrophoblast**.

### Final Answer:
The multicellular, multinucleate, irregular mass of the embryo that passes into the uterine wall is **C) syncytiotrophoblast**.