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Human skin is the site of many complex structures and dynamic processes as demonstrated in Figure 1-1 and Table 1-1. These processes include barrier and immunologic functions, sensation, vitamin D synthesis, thermoregulation, and protection from ultraviolet (UV) light and trauma.

Figure 1-1.

Cross-section of skin. Diagram showing layers of the skin, appendages, blood vessels, sensory nerve fibers, and sensory receptors.

Table 1-1.Structure and Function of the Skin


One of the most important function of human skin is to act as a barrier between us and the external environment.1 It protects against a variety of forms of physical damage, ranging from desiccation to infection, heat loss, and UV damage.2 The skin is a multilayered stalwart against these insults. First, the stratum corneum, with its corneocytes wrapped in cornified cell envelopes, water-impenetrable lipid lamellae, and filaggrin, forms a barrier that protects us from infectious organisms and water loss. Tight junctions help seal the spaces between neighboring cells in the stratum granulosum. Langerhans cells in the ...

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