The epidermis is the most superficial layer of the skin and provides the first barrier of protection from the invasion of foreign substances into the body. The principal cell of the epidermis is called a keratinocyte. The epidermis is subdivided into five layers or strata, the stratum germinativum (SG), the stratum spinosum(SS), the stratum granulosum(SGR), the stratum lucidum(not seen in this photomicrograph) and the stratum corneum(SC) in which a keratinocyte gradually migates to the surface and is sloughed off in a process called desquamation.
