This is the part of the skin contacting the external environment. It is epithelium of the stratified squamous type and is keratinized. A single layer of columnar cells resting on the basal laminae. These cells are highly mitiotic and give rise to the cells seen in the stratum spinosum. Layer of variable thickness consisting of more flattened cells.
Mitotic figures are common.
Cell contacts are desmosomal and important in forming part of the Barrier function of skin. Composed of from 1 to 5 layers of flattened cells. They contain keratohyaline granules . Desmosomal contacts present. A thin layer of clear cells found only in thick skin.