Name the embryonic layer from which heart, blood and blood vessels develop.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the embryonic layer responsible for the development of the heart, blood, and blood vessels.

2. **Identifying the Embryonic Layers**: During embryonic development, there are three primary layers formed: ectoderm, mesoderm, and endoderm. Each layer gives rise to different organs and systems in the body.

3. **Defining Organogenesis**: The process of organ formation from these layers is known as organogenesis. It is essential to understand which organs develop from which layer.

4. **Listing the Functions of Each Layer**:
- **Ectoderm**: This layer develops into the skin, nervous system, eyes, and ears.
- **Mesoderm**: This layer is crucial for the development of the heart, blood, and blood vessels.
- **Endoderm**: This layer gives rise to the elementary canal, respiratory system, and excretory system.

5. **Final Answer**: Since the heart, blood, and blood vessels develop from the mesoderm, the answer to the question is **mesoderm**.

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