Stratum basale: single layer of cuboidal to columnar shaped cells. It is separated from the dermis by the basement membrane. Some cells move toward the surface while others migrate into the dermis and gives rise to sweat and oil glands. Many mitotic cells are seen. About 25% of the cells in this layer are melanocytes. Stratum spinosum: contains 5-10 rows of cells fitted closely together. The surface of the cells display minute spiney projections. Mitosis occurs here but not as frequently. Langerhans cells are scattered among the keratinocytes. Because cells superficial to this layer do not receive adequate nutrients, they become less viable and finally begin to die. Stratum granulosum: thin zone consisting of 3-5 layers of flattened cells. Keratinization begins in this third epidermal layer. The plasma membranes of these cells also thicken so that they become more resistant to destruction. Langerhans cells are also found in this layer. At the upper border of this layer, the cells die and lysosomes begin to digest their organelles. Stratum lucidum (clear layer):
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