Keratinized Oral Epithelium: Structure, Layers, And Function

Keratinized Oral Epithelium: Structure, Layers, And Function

Classify oral mucous and describe keratinized mucosa.
Answer:

Keratinized mucosa:

• Keratinizing oral epithelium has keratinocytes arranged in four cell layers.

1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratym corneum.

The mucosal surface results from the formation of a surface layer of keratin and the dying process of maturation is called keratinization.

1. Stratum basale:

• It is also called the proliferative or germinative layer.
• It is made up of a single layer of cuboidal cells that synthesize DNA and undergo mitosis to provide new cells.
• They contain bundles of tonofibrils and other cell organelles indicative of protein synthesis.
• The cells in this layer are capable of cell division.
• They divide and form two cell populations.
• One cell population migrate and form cells of the other layer.
• Other cell populations remain as stem cells.
• This layer contains desmosomes – connecting adjacent cells and hemidesmosomes – connecting cells to the basal lamina.
• They provide mechanical linkages.
• Gap junctions allowing electrical and chemical communications are also seen.

2. Stratum spinosum or prickle cell layer:

• Contains several rows of large elliptical or spherical cells.
• Membrane-coating granules appear in the upper part of this layer.
• The nuclei stain less intensely than those of the basal layer.
• They frequently shrink away from each other, remaining in contact only at points known as intercellular bridges.
• This gives the cells a spiny or prickle-like appearance.
• Cells of this layer are the most active in protein synthesis.
• Separation of cells occurs which is caused by loss of intercellular bridges – acantholysis.
• The basal and prickle cell layers together constitute from half to two-thirds of the thickness of the epithelium.

3. Stratum granulosum:

• This layer contains flattened cells containing basophilic keratohyalin granules associated with dense tonofibrils.
• Membrane-coating granules fuse with the cell membrane in the upper part.
• The nuclei of cells show signs of degeneration and pyknosis.
• The cell surfaces become more regular and more closely placed adjacent cell surfaces.
• This layer still synthesizes proteins.
• The membrane-coating granules are glycolipids that have an internal lamellated structure.
• This form an intercellular lamellar material that contributes to the formation of a permeable barrier.

4. Stratum corneum:

• This layer contains extremely flattened and dehydrated cells.
• Cell organelles have been lost.
• Cells are filled only with packed fibrillar material.
• Cells stain bright pink with eosin.
• The keratohyalin granules have disappeared.
• Cells do not synthesize proteins.

Orthokeratinization:

• Cells do not have any nuclei.

Parakeratinization:

• Cells retain pyknotic and condensed nuclei.
• Keratohyalin granules may be present in the cells.
• Cells also contain partially lysed cell organelles until they desquamate.