Skull Anatomy

The Skull

 The skull is made up of 22 bones: the cranium includes eight bones that surround and protect the brain and 14 bones that form the face. In adults, all but one of the skull bones 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, the only moveable skull bone, allows the mouth to open and close.

 In newborns, the skull bones are not completely fused; they are linked by fibrous membrane called fontanelles. Fontanelles allow the skull to be compressed slightly during birth and accommodate growth of the brain during early infancy. By one-and-a-half years of age, the skull sutures have formed and the fontanels have disappeared. 

Cranial Bones

The frontal bone forms the forehead. Two parietal bones form the sides of the cranial roof. Two temporal bones form the lower cranial sides. The occipital bone forms the cranial rear and floor. The ethmoid bone forms part of the nasal cavity. Shaped like a butterfly, the sphenoid bone forms the middle part of the cranial floor.

Facial Bones

The 14 facial bones provide the structure of 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, and the mandible forms the lower jaw. The maxillae and mandible secure the teeth.

                           

 Small holes in the skull bones, called foraminae, and canals enable blood vessels, such as the carotid arteries and nerves, to enter and leave the skull. The spinal cord passes through a 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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Categories: anatomy