,
The skin is a vital part of the body's temperature regulation system, protecting us against hypothermia and hyperthermia, both of them may be fatal (specialized vascular structures of the dermis/insulation by fat in subcutaneous tissue/evaporation of sweat).
エクリン発汗、アポクリン発汗、脂質の分泌、サイトカインの分泌。
食事から摂取されたプロビタミンD3は紫外線によってビタミンD3になる。 ビタミンD3は肝臓及び腎臓で水酸化されて活性型に転じ,PTHとともに血中のカルシウムを増加させる。
Vitamin D3 (cholecalciferol) is produced in the skin by the action of ultraviolet light on dehydrocholesterol. It is then hydroxylated in the liver and kidneys (needs parathyroid hormone to activate alpha-hydroxylase) to 1,25 dihydroxycholecalciferol, the active form of vitamin D. This anti-rachitic vitamin acts on the intestine increasing calcium absorption (through stimulation of synthesis of calcium-binding proteins in the mucosal cells of the intestine), as well as on the kidneys promoting calcium reabsorption.
わずかながら外気とガス交換する。
The skin is also part of the innate immunity (natural resistance) of the body against invasion by micro-organisms. The dryness and constant desquamation of the skin, the normal flora of the skin, the fatty acids of sebum and lactic acid of sweat, all represent natural defense mechanisms against invasion by micro-organisms. Langerhans cells present in the epidermis have an antigen-presenting capacity and might play an important role in delayed hypersensitivity reactions. They also play a role in immunosurveillance against viral infections. Langerhans cells interact with neighboring keratinocytes, which secrete a number of immunoregulating cytokines, and epidermotropic T-cells forming the skin immune system: SALT (skin associated lymphoid tissue).