e. Tooth Characteristics. An individual tooth may be identified by its position;
for example, maxillary left central incisor. It may also be identified by its anatomical
form since each tooth has its own particular characteristics which set it apart from any
other. Some teeth, for instance, have cutting or incisal edges (example: incisors), and
others have cusps (cone-like projections of the crowns). Normally when the jaws are
closed, the cusps interdigitate (interlock). The teeth are then said to be "in occlusion."
f. A Small Space. With the teeth in occlusion, there is a space distal to
(posterior to) the most posterior molar. This space connects the vestibule with the oral
cavity. It is useful to note that when a person's jaws are wired together, as with a
fractured jaw, that liquefied food can be provided through this natural opening.
The mouth, nose, sinuses, eyelids, throat, and digestive tract are lined with
mucous membrane. The mucous membrane lining the oral cavity is called oral mucosa.
It covers the inside of the cheeks and lips and the bony process (alveolar process) in
which the teeth are embedded. This covering of the alveolar process (which surrounds
the necks of the teeth) is called the gingiva or gum tissue. Oral mucosa serves as a
protective covering for the soft tissues of the mouth, much like skin protects outer
surfaces of the body. Mucous membrane is a tissue similar in composition to the skin.
It differs from skin mainly in having many mucous glands which bathe its surface. It is
also softer and not as tough as skin. Normally, mucous membrane has a pink color.
Healthy gingiva is pale coral pink and firm. In persons with darker skin, the gingiva may
have dark pigmentation as well. When diseased, the mucous membrane may be bright
red, indicating certain vitamin deficiencies, or it may be very pale pink, indicating
anemia. The color of oral mucosa can aid in disease diagnosis.
THE ORAL CAVITY
The oral cavity is bounded in front (anteriorly) and on the sides (laterally) by the
gingival and lingual surfaces of the teeth. It opens posteriorly into the pharynx, which is
a funnel-shaped space joining the nose and mouth with the passages (trachea and
esophagus), leading to the lungs and stomach.
a. Roof of the Mouth. The roof of the mouth is shaped like a vault (arched). It
consists of the hard palate, anteriorly, and the soft palate, posteriorly, which together
are called the palate. The hard palate is the hard part of the roof of the mouth, which
makes up about two-thirds of the palatal area. It is covered with mucous membrane,
which is closely adherent to the inferior surface of the maxilla. The maxillary bone gives
the palate its vaulted form. The soft palate, the posterior one-third, is continuous with
the hard palate. It has no bony foundation and consists of soft tissue, chiefly muscles,
lined with mucous membrane. Its posterior border hangs free and has an arched
shape. The soft palate is elevated during swallowing to completely separate the oral
and nasal cavity.