Gross Anatomy of a Skull

The head consists of the skull, face, scalp, teeth, brain, cranial nerves, meninges, special sense organs, and other structures such as blood vessels, lymphatics, and fat. It is also the site where food is ingested and air is inspired and expired (Fig. 101; Fig. 102). Diseases of important structures in the head form the bases of many medical, dental, and surgical specialties dentistry, maxillofacial surgery, neurology, neuroradiology, neurosurgery, neuropsychiatry, oral surgery, maxillofacial surgery, ophthalmology, oral surgery, otology, psychiatry, and rhinology. The skull is the skeleton of the head; a series of bones form its two parts, the neurocranium and facial skull. The neuro-cranium ('brain box' or cranial vault) provides a case for the brain and cranial meninges (membranes covering the brain), proximal parts of the cranial nerves, and blood vessels. The term cranium (means skull) is sometimes restricted to a skull without the mandible. The cranium has a domelike roofthe calvaria skullcap (Fig. 103) and a floor or cranial base (basicranium) consisting of the ethmoid bone and parts of the occipital and temporal bones (Fig. 104). The facial skeleton consists of the bones surrounding the mouth and nose and contributing to the orbits (eye sockets, orbital cavities). In the anatomical position, the skull is oriented so that the inferior marain of the orbit (eye socket) and the superior margin of the external acoustic meatus (auditory canal) are horizontal. This is called the orbitomeatal plane (Frankfurt plane). THE NEUROCRANIUM in adults is formed by eight bones: 1. A frontal bone (os frontale), 2. Paired parietal bones (os parietale), 3. Paired temporal bones (os temporale), 4. An occipital bone (os occipitale), 5. A sphenoid bone (os sphenoidale), 6. An ethmoid bone (os ethmoidale). Most of these bones are largely flat, curved, and united by fibrous interlocking sutures. During childhood, some bones are united by hyaline cartilage (synchondroses) between the occipital and sphenoid bones. A number of irregular bones form the framework of the face and cranial base. 1. THE FRONTAL BONE specifically its squamous (flat) part forms the skeleton of the forehead, articulating inferiorly with the nasal and zygomatic bones (Fig. 105). In the fetal skull, the frontal suture separates the two halves of the frontal bone, and they remain separate until approximately 6 years of age. The smooth, broad, convex plate of bone called the frontal squama. The frontal articulates with twelve bones: the sphenoid, the ethmoid, the two