Thymus gland develops from embryonic :

Options

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

Answer

**Step-by-Step Solution:**

1. **Understanding Germ Layers**:
- In embryonic development, there are three primary germ layers: ectoderm, mesoderm, and endoderm. Each layer gives rise to different tissues and organs in the body.

2. **Identifying the Germ Layer for Thymus Gland**:
- The thymus gland specifically develops from the endoderm, which is the innermost germ layer.

3. **Formation of the Thymus**:
- The thymus originates from two hollow elongations of the endoderm during embryonic development. These elongations eventually fuse to form the thymus gland.

4. **Function of the Thymus Gland**:
- The thymus gland plays a crucial role in the immune system. It produces hormones such as thymosin, which are essential for the differentiation of T lymphocytes (a type of white blood cell) and for enhancing the production of antibodies.

5. **Conclusion**:
- Therefore, the thymus gland develops from the embryonic endoderm.

**Final Answer**: The thymus gland develops from embryonic endoderm.

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