The lining of the oral cavity serves a variety of functions, including protection, sensation, and secretion, and is histologically adapted to the unique environment inside the mouth.
Oral mucosa lacks the appendages seen in skin, although sebaceous glands can be found in the upper lip and buccal mucosa
in approximately 75% of adults. Submucosal minor salivary glands are found throughout the oral cavity, with highest concentrations
in the palate and lower lip.
Aggregates of lymphoid tissue can also be found in the oral cavity,
however, the largest collection of lymphoid tissue is seen posteriorly and known as Waldeyer ring. This consists of the palatine, lingual, and adenoid (pharyngeal) tonsils, and virtually encircles the entrance to the oropharynx. Small nodules of accessory tonsil
tissue are often seen on the posterior wall of the oropharynx and may become enlarged with inflammation or infection and mistaken for a suspicious mass.
Normal pits and depressions in tonsil tissue (tonsillar crypts) may become plugged with keratin or other debris and form cysts which appear yellow to white in color consists of a stratified squamous epithelium which continually renews itself by division of progenitor cells in the deeper basal layer.
Lobulated tonsils with cyst evident in the superior right
tonsillar pole (long solid arrow). Note blunted and slightly bifid
tip of uvula. Posterior pillar is marked with a broken arrow
New cells show progressive maturation as they migrate to the surface layers, which are subsequently shed. Areas of the mouth
that receive a greater degree of masticatory stress, namely the hard palate, tongue dorsum, and gingiva, are lined with keratinized mucosa, giving more protection against friction and abrasion. This tissue is more firmly attached to the underlying periosteum, which prevents damage from shearing forces.
Normal stratified squamous epithelium. The basal cells are cuboidal
and abut the basement membrane. The shape becomes more flattened (squamoid) as the cells mature and move toward the
surface. Irregularly shaped spinous, or prickle, cells are present in the intermediate layers. Surface keratin keratin is also
present in this diagram. The connective tissue layer below the basement membrane contains blood vessels, lymphatics,
fatty tissue, fibrous and elastic tissues, bone, and muscle
The mucogingival junction, where the mobile mucosa lining the vestibule and floor of mouth joins the tightly adherent gingiva of the dental alveolus, should be easily visible in the healthy state. The gingiva appears paler pink secondary to decreased visibility of underlying blood vessels through the relatively opaque keratin layer. The gingival margin should be well defined with
slightly rolled margin and pointed interdental papillae.
Healthy tissue will exhibit stippling, representing collagen
fibers attaching the gingiva to the underlying periosteum.
Maxillary labial vestibule showing healthy appearing
soft tissues with gingival stippling (solid arrow), rolled gingival
margin (broken arrow), and sharp interdental papillae (asterisk).
Note wear on incisal edges of maxillary central incisors.