Bones of cranium

The bones of cranium, along with the mandible, make up the human skull. Although the term "skull" includes the mandible, strictly speaking, the cranium comprises all the skull's bones, excluding the mandible or lower jaw. However, the terms "skull" and "cranium" are often used interchangeably.

The human cranium is divided into two main parts: the neurocranium and the viscerocranium.

The neurocranium forms the protective bony case around the brain, further divided into the skull cap (calvaria) and the base, which houses the cranial cavity. It consists of 8 bones: 2 paired (parietal and temporal) and 4 unpaired (frontal, occipital, sphenoid, and ethmoid). Including the 3 pairs of ear ossicles (malleus, incus, and stapes) in the middle ear cavity, the neurocranium has a total of 14 bones.

The viscerocranium forms the facial skeleton and includes 13 bones: 6 paired (maxilla, zygomatic, nasal, lacrimal, palatine, and inferior nasal concha) and 1 unpaired (the vomer).

Thus, the total number of bones in the cranium, including the ear ossicles, is 27. Adding the mandible, the overall count for the skull is 28 bones.

The bones of cranium (or skull) are connected by special joints called sutures. At birth, though, these bones are not completely fused, leaving spaces called fontanelles. These gaps allow the bones to overlap during childbirth and grow as the brain expands. The joints between the ear ossicles are synovial. Similarly, the temporomandibular joint in the skull is also a synovial joint.