What is a skull? State its function.

Explanation

### Step-by-Step Text Solution:

1. **Definition of Skull**: The skull is a bony structure that forms the head in vertebrates. It consists of 95% immovable bones that create the shape of the head and face.

2. **Composition of the Skull**: The skull is primarily made up of bones that are fixed in place, meaning they do not move. However, there is one bone in the lower jaw, known as the mandible, which is movable.

3. **Protection of Vital Organs**: The primary function of the skull is to protect the brain, which is one of the most important organs in the body. The hard structure of the skull acts as a shield against physical impacts.

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