Now we’ll move on to take an overall look at the oral cavity, and at some important, closely related structures. We’ll look first at the shape and extent of the oral cavity, then we’ll look at the muscles of the cheek and lips, then at the teeth, then at the salivary glands.
To understand the shape of the oral cavity, and its extent, we’ll look at it in a living model. Here’s the tongue, here’s the palate, here’s the inner aspect of the alveolar process of the maxilla, and of the mandible.
The alveolar processes of the maxilla, and mandible, together with the upper and lower teeth, project into the oral cavity from above and below. They divide the oral cavity into an inner part, and an outer part.
The upper and lower gums, or gingivae, are formed by mucous membrane that covers the alveolar processes on the outside, and on the inside.
The outer part of the oral cavity, the vestibule, lies between the teeth and gums on the inside, and the cheek and lips on the outside. The mucous membrane of the lips and the cheek is continuous above and below with the mucous membrane of the gums.
The inner part of the cavity is closed off above by the hard palate, and further back by the soft palate, which ends back here at the uvula. It's closed off below largely by the tongue, and also by the mucous membrane of the floor of the mouth.
To see the features of the posterior part of the oral cavity, we’ll look at a dissected specimen that’s been divided in the mid-line. This specimen is missing a number of teeth.
The mucous membrane that lines the cheek passes medially behind the last molar teeth and becomes continuous with the mucous membrane of the inner part of the oral cavity. The front of the ramus of the mandible is here. To look at the wall of the oral cavity further back, we’ll move the soft palate backward.
This fold in the mucous membrane running from the soft palate to the side of the tongue is the palatoglossal arch. It acts as a dam, preventing liquid from spilling backward past the side of the tongue. This less noticable fold is the palatopharyngeal arch.
This triangle between the two arches is occupied in early life by a prominent mass of lymphoid tissue, the tonsil. In later life, as in this specimen, the tonsil atrophies. Here’s the palatoglossal arch in a young person. Here behind it is the tonsil.
We’ll look at the soft palate along with the pharynx, at the end of this section.