Differentiated Structural Components of the Keratinocyte

Keratinocytes are the principal cell type of stratified squamous epithelia. These epithelia cover both external surfaces (skin, cornea, conjuctiva) and internal surfaces (pharynx, esophagus, mouth, vagina), always acting as a barrier between the body and a foreign environment. The chemical and physical resistance of epidermis is much increased by a layer of dead cells (cornified layer) that adheres to its outer surface; yet, even without such a layer, other stratified squamous epithelia can resist conditions unfavorable for the survival of most cell types; oral and esophageal epithelia, for example, also withstand physical abrasion and extremes of temperature and pH.