Skull cap bone

The calvarium, also known as the roof or skull cap, consists of three bones: Frontal bones. Parietal bones. Occipital bones.

Bones are composed of bone matrix, which has both organic and inorganic components. Bone matrix is laid down by osteoblasts as collagen, also known as osteoid. Osteoid is hardened with inorganic salts, such as calcium and phosphate, and by the chemicals released from the osteoblasts through a process known as mineralization.

The basic microscopic unit of bone is an osteon (or Haversian system). Osteons are roughly cylindrical structures that can measure several millimeters long and around 0.2 mm in diameter.