Skull: Lateral View

The lower face is supported by both the maxillary alveolar processes and the mandible. The inferior margin of each maxilla projects downward as the curved alveolar process, which unites in front with its fellow to form the U-shaped alveolar arch containing the sockets for the upper teeth. The roots of the teeth produce slight surface elevations, the most obvious of which are produced by the canine teeth. The upper border of the body of the mandible is called the alveolar part and contains sockets for the lower teeth, whose roots also produce slight surface elevations.

Viewed from the side, the skull is divided into the larger ovoid braincase and the smaller facial skeleton. The two are connected by the zygomatic bone, which acts as a yoke (zygon) between the temporal, sphenoid (greater wing) and frontal bones, and the maxilla. Other features on the lateral aspect of the skull include parts of the sutures between the frontal, parietal, sphenoid, and temporal bones (which form most of the braincase), and the sutures between such facial bones as the nasal, lacrimal, ethmoid, and maxilla. Clearly seen are the parts of the mandible and the temporomandibular joint, the external acoustic meatus and the various foramina that transmit nerves and vessels of the same name. Not readily visible are the foramen ovale and the foramen spinosum.

Certain features deserve particular mention. The curved superior and inferior temporal lines arch upward and backward over the frontal bone from the vicinity of the frontozygomatic suture, pass over the coronal suture and the parietal bone, and then turn downward and forward across the temporal squama to end above the mastoid process. The superior and inferior temporal lines provide attachments, respectively, for the temporal fascia and the upper margin of the temporal muscle, which occupies most of the temporal fossa. This fossa is bounded above by the superior temporal line, and below it is bounded by the infratemporal crest, separating the greater wing of the sphenoid bone from the pterygoid processes. The anteroinferior corner of the parietal bone usually fills the angle between the greater wing of the sphenoid and the frontal bone, although sometimes the squamous part of the temporal bone may extend forward to articulate directly with the frontal bone, thus excluding the sphenoid. This area is the pterion, and its internal surface is deeply grooved by the anterior branches of the middle meningeal vessels. It is situated about 3.5 cm behind the frontozygomatic suture (usually palpable as a slight ridge) and 4 cm above the zygomatic arch. As the most common site of damage to these vessels from a skull fracture, it is a surgical landmark.

The infratemporal fossa is an irregular space lying below the infratemporal crest. It is continuous above with the temporal fossa through the gap between the crest and the zygomatic arch. It is bounded medially by the lateral plate of the pterygoid process and the infratemporal surface of the maxilla, and laterally, by the ramus of the mandible. It communicates through the pterygomaxillary fissure with the pterygopalatine fossa.

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