mucosa 2

Study Notes

The surface epithelium of oral mucosa is characterized by three main types of keratinization: orthokeratinization, parakeratinization, and incomplete parakeratinization.

Orthokeratinization is a type of keratinization characterized by a keratinized layer composed of up to 20 layers of squames, thicker than most skin except soles and palms.
Squames are hexagonal disks that become dehydrated and flattened, making them more resistant to mechanical damage and chemical solvents.
Squames are shed through desquamation and replaced by cells from underlying layers, helping to limit colonization and invasion of epithelial surfaces by pathogens like Candida.
The process of desquamation occurs rapidly, with surface squames being shed in a matter of hours.

The stratum corneum is the outermost layer of the oral epithelium, composed of flattened cells with no nuclei.
The cells of the keratinized layer contain keratin filaments embedded in a matrix of filaggrin, a protein that facilitates dense packing.

The stratum granulosum consists of larger, flattened cells containing small keratohyalin granules that stain intensely with acid dyes.
Keratohyalin granules are irregularly shaped, 0.5-1 micrometer in size, and are synthesized by ribosomes.
Keratohyalin granules are associated with tonofibrils and form the matrix in which keratin filaments are embedded.

The stratum spinosum consists of several rows of larger, elliptical or spherical cells.
Cells in this layer shrink away from each other, remaining in contact only at intercellular bridges or desmosomes, giving them a spiny or prickle-like profile.

The stratum basale is a layer of cuboidal or columnar cells adjacent to the basement membrane.
Cells in this layer are capable of division, but this is a functional classification not discernible from appearances in normal histologic sections.

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