Skin

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The skin is the largest human organ and serves as a barrier against external influences. It fulfils a variety of functions, including protection, temperature regulation and sensory perception. Humans have two skin types, hairy and glabrous skin. The latter is mainly found on the palms and soles. Histologically, the skin is divided into epidermis, dermis (corium) and subcutis.

The epidermis is the top, thin layer of the skin and consists of a multilayered, keratinized squamous epithelium. It is further divided into five layers, which from basal to apical are as follows:

• Stratum basale.
• Stratum spinosum.
• Stratum granulosum.
• Stratum lucidum, which only occurs in the groin skin.
• Stratum corneum.

The main cells of the epidermis are the keratinocytes, which are responsible for the production of keratin. There are also melanocytes, which produce the pigment melanin, Langerhans cells, which play a role in the immune system, and Merkel cells, which are involved in sensory perception.

Many collagen and elastin fibers are embedded in the thick, connective tissue dermis (corium), which give the skin elasticity and strength. Blood vessels, nerves, hair follicles as well as sweat and sebaceous glands are also found here. The lowest layer, the subcutis, is composed of loose connective tissue and fat cells and serves as an energy storage and insulating layer.

Watch the following video to learn more about the histological appearance of the skin and its layers:

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