What is bone narrow? Give its function.

Explanation

### Step-by-Step Solution

1. **Definition of Bone Marrow**: Bone marrow is a specialized type of vascular adipose tissue found within the cavities of bones, particularly in the spongy tissue of long bones such as the femur (thigh bone).

2. **Location**: It is primarily located in the medullary cavities of long bones and in the spaces of spongy bone.

3. **Composition**: Bone marrow contains stem cells, which are undifferentiated cells capable of developing into various types of blood cells.

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