Physiology of the skin

The skin is the main interface between the individual and the environment. It has essential physiological functions which allow the individual to live safely, even under changing external conditions which might pose potential threats. The most important physiological function of the skin is protection against various forms of noxious stimuli including physical and chemical trauma, micro-organisms and radiation. The skin and its appendages are also vital for thermoregulation. Several modalities of sensation are mediated via the skin allowing the individual to recognize the context of their relationship to the environment. The skin is a significant water-storage organ. Although it mainly acts as a barrier, the skin does have some ability to absorb various substances, particularly lipophilic compounds. Synthesis of vitamin D occurs in sun-exposed skin and is the major site of production in normal health. It is important for surgeons to understand the functions of the skin and the process of wound healing in order to recognize when clinical problems occur and to appreciate how patients with disordered skin physiology are likely to respond to traumatic or surgical injury.