THE NORMAL ORAL MUCOSA
The oral mucosa functions as a barrier that protects the un-
derlying tissue against mechanical, chemical and thermal
damage, e.g., during food intake. It also exerts essential
sensory functions. The physical and immunological barrier
functions, which provide an effective barrier against invading
microorganisms, are crucial for mucosal immunity, mainte-
nance of a balanced microbiota and an intact oral mucosa.
The oral mucosa comprises a multilayered squamous epi-
thelium and an underlying connective tissue. The stratified
squamous epithelium of the oral mucosa is characterised
by regional variations mainly related to differences in the
degree and type of keratinisation of the epithelium, reflecting
the various functions of the oral mucosa. The oral mucosa
is classified into lining, masticatory and specialised types
of oral mucosa reflecting its functions in different regions
of the oral cavity. Lining, non-keratinised mucosa is found
in areas where there is a need for movement and flexibil-
ity, for example in relation to food processing and speech
(e.g. cheeks, floor of the mouth and alveolar mucosa), while
masticatory, keratinised mucosa is found in areas highly ex-
posed to mechanical and thermal impact (dorsal part of the
tongue, gingiva and hard palate). The tongue mucosa belongs
to the specialized mucosa due to papillae comprising taste
buds and filiform papillae. It is important to have insight
in the structure and functions of the normal oral mucosa in
order to understand the different reaction patterns of the
oral mucosa, and thus be able to make a relevant diagnosis
when recognizing clinical changes in the oral mucosa. In this
short overview, the normal structure of the oral mucosa is
reviewed, including the regional variations, and the functions
of the oral mucosa.