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.