Unit2. Cells and AgingAging is a normal process accompanied by a progressive alteration of the bodys homeostatic adaptive responses; the specialized branch of medicine that deals with the medical problems and care of elderly person is called geriatrics.衰老是一种正常的生理过程，伴有机体内环境稳定适应性应答的进行性改变。研究老年人的健康问题和保健的一门特殊医学分支被称作老年病学The obvious characteristics of aging are well known; graying and loss of hair, loss of teeth, wrinkling of skin, decreased muscle mass, and increased fat deposits. The physiolo
