6: The Skull

Chapter 6 imageThe Skull

1 Introduction

The skeleton of the head is a complex articulation of many bones and teeth, which are collectively referred to as the skull or cranium. On the basis of function the skull may be conveniently divided into two main areas: the (1) neurocranium and (2) the facial skeleton (Figure 6-1).

2 Views

The skull is traditionally studied by rotating the skull to various views. By convention, however, the skull is described as oriented in the horizontal Frankfort plane, which is a plane that joins the uppermost points of the right and left external auditory meatuses (ear holes) and the lowermost points of the right and left orbits. The Frankfort plane is parallel to the floor or tabletop and approximates the anatomical position.

FRONTAL VIEW

Bones

The bones evident in the anterior view (Figure 6-2, A) are the right and left maxillae, nasal bones, the right and left zygomatic bones, the right and left lacrimal bones, the right and left inferior conchae, the ethmoid bone, the vomer, the sphenoid bone, the frontal bone, and the mandible.

Features

Orbital Openings

The Jaws

The upper and lower jaws house the teeth. The upper jaw is fixed and consists of two bones; the lower jaw, or mandible, is movable and is one bone in the adult.

LATERAL VIEW

Features

The Cranial Vault Region

The cranial vault is formed anteriorly by the single frontal bone, laterally by the paired parietal bones, and posteriorly by the single occipital bone. Inferolaterally the walls of the vault are formed by the paired temporal bones and the paired greater wings of the single sphenoid bone. The cranial vault region presents the following features.

The Infratemporal Region

The infratemporal region is obscured by the ramus of the mandible, which serves as the lateral wall of the region (Figure 6-5). With the mandible removed, the limits of the infratemporal region can be further delineated. The infratemporal region is separated from the temporal fossa above by an indistinct infratemporal crest.

Features

POSTERIOR VIEW

The most prominent feature of the posterior view is the rounded posterior pole of the skull, called the occiput (see Figure 6-7). Hence, the area is often referred to as the occipital area.

Features

The posterior aspect of the skull also includes three nuchal lines, which are raised ridges that represent areas of attachment for neck muscles.

The following features are in a straight line traversing the base of the posterior aspect of the skull from lateral to medial.

BASAL OR INFERIOR VIEW

Bones

The bones seen from the basal aspect (Figure 6-8, A) are the right and left maxillae (palatal processes), the right and left palatine bones (palatal processes), the sphenoid bone (body, pterygoid processes, and greater wings), the vomer, the right and left temporal bones, and the occipital bone.

Features

Anterior Region

The pterygoid process consists of a lateral and a medial plate. The lateral plate provides attachment for both lateral and medial pterygoid muscles. The medial pterygoid plate forms the posterior limit of the lateral wall of the nasal cavity. The medial plate ends inferiorly as the hamulus, a small, slender hook.

Intermediate Area

From lateral to medial, the features encountered in the intermediate area are as follows (see Figures 6-8 and 6-9):

INTERNAL ASPECT OF THE BASE

To expose the internal features of the skull, the skullcap (calvaria) is sawn off and removed.

Middle Cranial Fossa

Features of the middle cranial fossa include the following:

1 The sella turcica (Figure 6-11), which translates as a “Turkish saddle.”

Posterior Cranial Fossa

Jan 5, 2015 | Posted by in General Dentistry | Comments Off on 6: The Skull
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