Skin anatomy, physiology, and pathophysiology.

Human skin is the largest multifunctional organ of the body, and knowledge of its structure and function is essential to clinicians and researchers. The skin has two layers, the epidermis and dermis, separated by a basement membrane zone. It provides protection, sensation, thermoregulation, biochemical/metabolic, and immune functions. Key and emerging concepts important to understanding pathophysiological mechanisms for practicing clinicians are: knowledge of differences between acute and chronic wounds; ability to evaluate depth and extent of injury; understanding stages of healing versus zones of activity; and knowledge of ischemic-reperfusion injury, the skin immune system, cytokines, growth factors and other biomolecules, and matrix synthesis and degradation. These concepts are addressed in this article.