In gastrula stage which layer are formed

Options

A. Ectoderm
B. Mesoderm
C. Endoderm
D. All

Answer

**Step-by-Step Solution:**

1. **Understanding the Zygote Stage:**
- The process begins with the formation of a zygote after fertilization. The zygote is a single cell that will undergo several divisions.

2. **Cleavage and Morula Formation:**
- The zygote undergoes cleavage, which is a series of rapid cell divisions. This results in the formation of a morula, which is a solid ball of cells typically consisting of 8 cells.

3. **Blastula Formation:**
- Further divisions lead to the formation of the blastula, which contains 64 to 128 cells. The blastula has a hollow structure with a fluid-filled cavity called the blastocoel.

4. **Implantation:**
- After the blastula stage, the embryo implants itself into the uterine wall, allowing for further development.

5. **Gastrulation:**
- Following implantation, the process of gastrulation begins. During this stage, the cells (blastomeres) of the blastula undergo morphogenetic movements.

6. **Formation of Germ Layers:**
- As a result of these movements, three primary germ layers are formed:
- **Ectoderm:** The outermost layer, which will develop into the skin and nervous system.
- **Mesoderm:** The middle layer, which will form muscles, bones, and the circulatory system.
- **Endoderm:** The innermost layer, which will develop into the digestive tract and other internal organs.

7. **Conclusion:**
- Therefore, during the gastrula stage, all three germ layers (ectoderm, mesoderm, and endoderm) are formed.

**Final Answer:**
In the gastrula stage, all three germ layers are formed: ectoderm, mesoderm, and endoderm.

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