In human embryo the extra embryonic membrane are formed by :

Options

A. Inner cell wall
B. Trophoblast
C. Formative cells
D. Foillcless cells

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the formation of extra embryonic membranes in a human embryo. Extra embryonic membranes are structures that provide support and protection to the developing embryo.

2. **Identifying the Key Structures**: In the context of a human embryo, the blastocyst is a crucial structure that consists of two main components: the trophoblast and the inner cell mass.

3. **Defining the Trophoblast**: The trophoblast is the outer layer of the blastocyst. It plays a significant role in the implantation of the embryo into the uterine wall and is responsible for forming extra embryonic membranes.

4. **Defining the Inner Cell Mass**: The inner cell mass is a group of cells located within the blastocyst. It is responsible for developing into the embryo itself and gives rise to the three germ layers (ectoderm, mesoderm, and endoderm) as well as the yolk sac.

5. **Identifying Extra Embryonic Membranes**: The extra embryonic membranes formed include:
- **Chorion**: Formed from the trophoblast.
- **Amnion**: Also formed from the trophoblast.
- **Allantois**: Formed from the trophoblast.
- **Yolk Sac**: Formed from the inner cell mass.

6. **Conclusion**: Since the question specifically asks which component forms the extra embryonic membranes, the correct answer is the **trophoblast**.

**Final Answer**: The extra embryonic membranes in a human embryo are formed by the **trophoblast**.

---