Layers of the epidermis
The epidermis is made up of 95% keratinocytes but also contains melanocytes, Langerhans cells, Merkel cells, and inflammatory cells. The stratum basale is primarily made up of basal keratinocyte cells, which can be considered the stem cells of the epidermis. They divide to form the keratinocytes of the stratum spinosum, which migrate superficially.
This image details the layers of the epidermis. Starting at the deepest level and rising to the top, it depicts the: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.
Source
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"Vitamin D."
http://en.wikipedia.org/wiki/Vitamin_D%23Production_in_the_skin
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