In looking at the jaws we’ll start, as always, with the bones. The word jaw is used in two ways. When we speak of “jaws" in the plural, we’re referring to both the upper jaw, the maxilla, and the lower jaw, the mandible. When we say “jaw“ in the singular, as in jaw movement or jaw bone, we’re referring to the mandible.
We’ll take a good look at the mandible in a minute. Before doing that, let’s take a fresh look at the parts of the facial skeleton that we’ll be seeing in this section. Here’s the zygomatic arch enclosing the temporal fossa, and the infratemporal fossa.
Here’s the joint surface of the temporomandibular joint, with the external auditory meatus and the styloid process just behind it. Here are the pterygoid plates, with the pterygoid fossa between them. This sharp projection just medial to the temporomandibular joint is the spine of the sphenoid bone.
The part of the maxilla that bears the teeth is called the alveolar process. We’ll look at the teeth later in this section. The alveolar process ends behind at the tuber.
Now we’ll bring the mandible into the picture. The mandible develops from two originally separate bones, one on each side, which fuse together here at the symphysis. The mandible is described as consisting of the body, and the right and left ramus.
The corner between the ramus and the body is the angle of the mandible. The rounded projection that articulates with the temporal bone is the condyle, or condylar process. The narrowing below the condyle is the neck.
The sharp, slender projection in front of the condyle is the coronoid process, a major muscle attachment, as we’ll see. The dip between the coronoid process and the condyle is the mandibular notch.
The angle of the mandible is roughened on the outside, and on the inside, by the insertions of a matching pair of muscles, the medial pterygoid on the inside and the masseter on the outside, which we’ll see shortly.
The body of the mandible is described as consisting of the base and the alveolar process. The side of the body slopes upward and inward, slightly on the outer aspect, markedly on the inner aspect. The posterior part of the alveolar process bulges medially above this hollow, the submandibular fossa.
This projection in the mid-line is the mental protuberance. On the inside, this roughened area is the mental spine; two pairs of muscles are attached here, the genio-hyoid and genioglossus muscles.
On the inner aspect of the mandible this thickening below the coronoid process is the buttress. In the middle of the ramus, level with the tops of the teeth, is the mandibular foramen. Just in front of it is a small upward projection, the lingula.
The mandibular foramen is the start of a tunnel for the inferior alveolar nerve and blood vessels. A major branch of the nerve emerges on the outside, at the mental foramen.