Cranial Anatomy

The bones of the skull and face are designed to protect the brain, provide structure for the face, and form the openings through which food, water, and air enter the body.

Did you know that the skull actually consists of 22 bones? Of these bones, eight make up surround and protect the brain, and the remaining 14 form the underlying structure of the face. The important elements of the human skull include:

The Cranium

The eight bones of the cranium form the “vault” that encloses the brain. They include the frontalparietaloccipitaltemporalsphenoid and ethmoid bones.

The frontal bone forms the forehead. The two parietal bones form the upper sides of the skull; the two temporal bones form the lower sides. The butterfly-shaped sphenoid bone is located at the base of the skull. The ethmoid bone, located at the roof of the nose between the eye sockets, separates the nasal cavity from the brain. The occipital bone forms the back of the skull.

In adults, all but one of the 22 bones of the skull are fused together by immovable joints called sutures. The sutures lock the edges of the skull bones together, like pieces in a puzzle, to form a structure that is both rigid and strong. The mandible, or lower jaw, is the only bone in the skull that moves, and it allows the mouth to open and close.

In newborns, the skull bones are not completely fused, but linked by soft, fibrous membranes called fontanels. Fontanels allow the skull to be compressed slightly during birth and accommodate growth of the brain during early infancy. By 18-24 months, the skull sutures typically have formed and the fontanels have disappeared.

Facial Bones

The 14 facial bones provide structure for the face and form the openings through which food, water, and air enter the body. Each of the following facial bones are paired: the maxillae form the upper jaw and front of the hard palate; the zygomatic bones form the cheeks; the nasal bones form the bridge of the nose; the lacrimal bones form part of the orbit, or eye socket; the palatine bones form the rear of the hard palate and the inferior nasal conchae divide the nasal cavity. The vomer is a single bone that makes up part of the nasal septum, which divides the nostrils. The two bones of the mandible form the lower jaw, and both the maxillae and mandible anchor the teeth.

Small holes in the skull bones, called foraminae, enable blood vessels, such as the carotid arteries and nerves, to enter and leave the skull. The spinal cord passes through the largest hole, called the foramen magnum, in the base of the cranium to join the brain. The occipital condyles on either side of the foramen magnum articulate with the first vertebra (C1) of the spine to permit up-and-down movement of the head.

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