Human skull. Coloured X-ray of a side view of a human skull. The fused bones of the cranium (centre) encase and protect the brain. The nasal, cheek and jaw bones form the facial skeleton (lower right). The lower jaw bone, or mandible, is attached at flexible joints, allowing it to move. The upper and lower jaw bones contain 32 permanent teeth (white, lower right). The skull rests on the first of seven spinal vertebrae that form the neck. A joint between the first and second vertebra enables the head to turn.