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The bony framework of the head: 22 bones that protect the brain and form the face, eye sockets, and jaw.
Medically reviewed & updated
The skull is the bony framework of the head and the most complex structure in the skeleton. In most adults it consists of 22 bones divided into two functional regions: the neurocranium, which encloses and protects the brain, and the viscerocranium (facial skeleton), which forms the face.
The neurocranium is made up of 8 bones: the frontal bone, two parietal bones, two temporal bones, the occipital bone, the sphenoid, and the ethmoid. Together they form the cranial vault (the dome that covers the brain) and the cranial base, which has openings for the spinal cord, blood vessels, and cranial nerves. The largest opening, the foramen magnum in the occipital bone, is where the brainstem connects to the spinal cord.
The viscerocranium comprises 14 bones, including the paired maxillae (upper jaw), zygomatic (cheek) bones, nasal bones, lacrimal bones, palatine bones, and inferior nasal conchae, plus the single vomer and the mandible (lower jaw). The mandible is the only freely movable skull bone, hinging at the temporomandibular joints to allow chewing and speech. The facial bones also form the orbits that hold the eyes and the framework of the nasal cavity.
Nearly all skull bones meet at immovable fibrous joints called sutures. The major ones include the coronal suture (between the frontal and parietal bones), the sagittal suture (between the two parietal bones), the lambdoid suture (between the parietal bones and the occipital bone), and the squamous sutures (along the temporal bones). In newborns, the bones are separated by soft membranous gaps called fontanelles ("soft spots") that let the skull flex during birth and accommodate rapid brain growth. The posterior fontanelle typically closes around 6 to 8 weeks, and the anterior fontanelle closes around 1 to 2 years of age.
The skull's main job is protection—shielding the brain, brainstem, and eyes from injury—and housing the organs of special sense. Premature fusion of sutures in infants (craniosynostosis) can distort head shape and limit brain growth. Skull fractures and changes in fontanelle tension can signal serious conditions. This page is educational and not a substitute for medical care.