mucosa 2

Surface Epithelium of Oral Mucosa

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

Orthokeratinization

• 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.

Stratum Corneum (Keratinized Layer)

• 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.

Stratum Granulosum (Granular Layer)

• 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.

Stratum Spinorum (Prickle-Cell Layer)

• 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.

Stratum Basale (Basal Layer)

• 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.