A keratinocyte is the principal epithelial cell of the epidermis and produces keratin intermediate filaments. Dividing basal keratinocytes supply descendants that differentiate, move toward the surface and form the protective barrier. Terminal differentiation changes both protein expression and cellular architecture; the outermost mature cells lose their nuclei. This continual renewal separates a proliferative compartment from a mechanically protective surface. [ref]
Molecular Biology of the Cell, 4th edition by Bruce Alberts and others. Chapter 22, Epidermis and Its Renewal by Stem Cells
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