In lower parts of the lateral portion of the calvaria, the frontal bone articulates with the greater wing of the sphenoid bone (Fig. 8.19), which then articulates with the parietal bone at the sphenoparietal suture, and with the anterior edge of the temporal bone at the sphenosquamous suture.
The junction where the frontal, parietal, sphenoid, and temporal bones are in close proximity is the pterion. The clinical consequences of a skull fracture in this area can be very serious. The bone in this area is particularly thin and overlies the anterior division of the middle meningeal artery, which can be torn by a skull fracture in this area, resulting in an extradural hematoma.
The final articulation across the lower part of the lateral portion of the calvaria is between the temporal bone and the occipital bone at the occipitomastoid suture.
A major contributor to the lower portion of the lateral wall of the cranium is the temporal bone (Fig. 8.19), which consists of several parts:
The squamous part has the appearance of a large flat plate, forms the anterior and superior parts of the temporal bone, contributes to the lateral wall of the cranium, and articulates anteriorly with the greater wing of the sphenoid bone at the sphenosquamous suture, and with the parietal bone superiorly at the squamous suture.
The zygomatic process is an anterior bony projection from the lower surface of the squamous part of the temporal bone that initially projects laterally and then curves anteriorly to articulate with the temporal process of the zygomatic bone to form the zygomatic arch.
Immediately below the origin of the zygomatic process from the squamous part of the temporal bone is the tympanic part of the temporal bone, and clearly visible on the surface of this part is the external acoustic opening leading to the external acoustic meatus (ear canal).
The petromastoid part, which is usually separated into a petrous part and a mastoid part for descriptive purposes.
The mastoid part is the most posterior part of the temporal bone, and is the only part of the petromastoid part of the temporal bone seen on a lateral view of the skull. It is continuous with the squamous part of the temporal bone anteriorly, and articulates with the parietal bone superiorly at the parietomastoid suture, and with the occipital bone posteriorly at the occipitomastoid suture. These two sutures are continuous with each other, and the parietomastoid suture is continuous with the squamous suture.
Inferiorly, a large bony prominence (the mastoid process) projects from the inferior border of the mastoid part of the temporal bone. This is a point of attachment for several muscles.
Medial to the mastoid process, the styloid process projects from the lower border of the temporal bone.
Visible part of the facial skeleton
The bones of the viscerocranium visible in a lateral view of the skull include the nasal, maxilla, and zygomatic bones (Fig. 8.19) as follows:
A nasal bone anteriorly.
The maxilla with its alveolar process containing teeth forming the upper jaw; anteriorly, it articulates with the nasal bone; superiorly, it contributes to the formation of the inferior and medial borders of the orbit; medially, its frontal process articulates with the frontal bone; laterally, its zygomatic process articulates with the zygomatic bone.