Main Model


CRANIUM : Zygomatic arch

Lateral Aspect of Cranium
The lateral aspect of the cranium is formed by both neurocranium and viscerocranium (Figs. 7.1A & B and 7.4A). The main features of the neurocranial part are the temporal fossa, the external acoustic meatus opening, and the mastoid process of the temporal bone. The main features of the viscero cranial part are the infratemporal fossa, zygomatic arch, and lateral aspects of the maxilla and mandible.

The temporal fossa is bounded superiorly and posteriorly by the superior and inferior temporal lines, anteriorly by the frontal and zygomatic bones, and inferiorly by the zygomatic arch (Figs. 7.1A and 7.4A). The superior border of this arch corresponds to the inferior limit of the cerebral hemisphere of the brain. The zygomatic arch is formed by the union of the temporal process of the zygomatic bone and the zygomatic process of the temporal bone.

In the anterior part of the temporal fossa, 3–4 cm superior to the midpoint of the zygomatic arch, is a clinically important area of bone junctions: the pterion (G. pteron, wing) (Figs. 7.4A and 7.6; Table 7.1). It is usually indicated by an H-shaped formation of sutures that unite the frontal, parietal, sphenoid (greater wing), and temporal bones. Less commonly, the frontal and temporal bones articulate; sometimes all four bones meet at a point.

The external acoustic meatus opening (pore) is the entrance to the external acoustic meatus (canal), which leads to the tympanic membrane (eardrum) (Fig. 7.4A). The mastoid process of the temporal bone is postero-inferior to the external acoustic meatus opening. Anteromedial to the mastoid process is the styloid process of the temporal bone, a slender needle-like, pointed projection. The infratemporal fossa is an irregular space inferior and deep to the zygomatic arch, and the mandible and posterior to the maxilla (see Fig. 7.67B).