Aging skin: histology, physiology, and pathology.

Skin is a complex organ covering the entire surface of the body. Aged skin is characterized by appearance of wrinkles, laxity, and pigmentary irregularities. These changes occur under the influence of intrinsic and extrinsic factors, with sun exposure being the most deleterious to the skin. Skin changes associated with aging are the focus of many surgical and nonsurgical procedures aimed to improve the appearance of skin. Knowledge of skin histology and physiology will deepen the understanding of cutaneous changes associated with aging and will promote optimal cosmetic and functional patient outcomes.