Nissl bodies are mainly composed of

Options

A. Free ribosomes and RER
B. Nucleic acids and SER
C. DNA and RNA
D. Proteins and lipids

Answer

### Step-by-Step Solution:

1. **Understanding Nissl Bodies**:
- Nissl bodies are large granular structures found in neurons. They are also referred to as Nissl substance.

2. **Function of Nissl Bodies**:
- The primary function of Nissl bodies is to synthesize and release proteins that are crucial for neuronal growth and the regeneration of axons.

3. **Composition of Nissl Bodies**:
- Nissl bodies are mainly composed of rough endoplasmic reticulum (RER) and free ribosomes. These components are essential for the synthesis of proteins.

4. **Conclusion**:
- Based on the composition, Nissl bodies are primarily made up of rough endoplasmic reticulum and free ribosomes.

5. **Final Answer**:
- Therefore, the correct answer is that Nissl bodies are mainly composed of rough endoplasmic reticulum and free ribosomes.