Epidermis (skin)

The epidermis is the outermost layer of the skin, composed of terminally differentiated stratified squamous epithelium, acting as the body's major barrier against an inhospitable environment. It is the thinnest on the eyelids at .05 mm and the thickest on the palms and soles at 1.5 mm.

Cellular components

The epidermis is avascular, nourished by diffusion from the dermis, and composed of four cell types: keratinocytes, melanocytes, Langerhans cells, and the Merkels cell. Keratinocytes are the major constituent, constituting 95% of the epidermis.

Layers

The epidermis is composed of 4-5 layers depending on the region of skin being considered. Those layers in descending order are the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. The term Malpighian layer refers to both the basal and spinosum layers.

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