Cerimele D, Celleno L, Serri F
Department of Dermatology, Catholic University, Rome, Italy.
Br J Dermatol. 1990 Apr;122 Suppl 35:13-20. doi: 10.1111/j.1365-2133.1990.tb16120.x.
The principal functions of the skin include protection, excretion, secretion, absorption, thermoregulation, pigmentogenesis, accumulation, sensory perception and regulation of immunological processes. These functions are all affected by the structural changes in the skin with ageing and, after middle age, most functions are reduced, some by as much as 50-60%. The physiological changes associated with these reductions include impairment of the barrier function, decreased turnover of epidermal cells, reduced numbers of keratinocytes and fibroblasts, and a reduced vascular network particularly around hair bulbs and glands. These changes result in fibrosis and atrophy, and decreases in hair and nail growth, vitamin D synthesis and the density of Langerhans cells. Production of epidermal thymocyte-activating factor, which enhances the T-cell response, is reduced leading to a decrease in the immune response; there is also a decreased functioning of Meissner's and Pacinian corpuscles. An increased generation of free radicals is observed. Certain environmental factors, particularly exposure to sun, accelerate the ageing of skin and are important in cutaneous carcinogenesis.
皮肤的主要功能包括保护、排泄、分泌、吸收、体温调节、色素生成、蓄积、感觉感知以及免疫过程调节。随着年龄增长，皮肤结构变化会影响这些功能，中年之后，大多数功能都会减退，有些功能的减退幅度高达50%-60%。与这些功能减退相关的生理变化包括屏障功能受损、表皮细胞更新减少、角质形成细胞和成纤维细胞数量减少，以及血管网络减少，尤其是毛囊和腺体周围的血管网络。这些变化会导致纤维化和萎缩，毛发和指甲生长、维生素D合成以及朗格汉斯细胞密度降低。增强T细胞反应的表皮胸腺细胞激活因子生成减少，导致免疫反应降低；梅斯纳小体和环层小体的功能也会减退。还观察到自由基生成增加。某些环境因素，尤其是阳光照射，会加速皮肤衰老，并且在皮肤癌发生过程中起重要作用。
