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The epidermis lies on the periphery of the skin and is divided into five layers (outer to inner): stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum germinativum (basale).
The stratum corneum includes anucleated cells, surrounded on the periphery by lipids to form a barrier against moisture. The stratum lucidum is also anucleated and is not always present. These cells are more commonly found in thick skin. The stratum granulosum is characterized in routine histological stains by the presence of keratohyaline granules. The stratum spinosum appears as a network of interconnecting cells that appear separated by spicules. These are the sites where desmosomes remain attached between dehydrated cells. This is an artefact of section preparation for light microscopy. The stratum germinativum has the basal cells that eventually evolve to become the more superificial layers.
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