ABSTRACT
The Aging Process From the single fertilized cell to maturity and then senescence, the human passes through several important stages. From conception to birth is one of these, followed by the growth of infanthood and childhood, followed by adolescence. Each of these stages is characterized by both an increase in cell number and a concerted and coordinated change in cell/ tissue/organ characteristics and function. Longitudinal growth of the skeleton is the most obvious feature accompanied by the growth and maturation of the muscles, the internal organs, the reproductive system, and the central nervous system. Once humans have attained maturity they maintain that stage for many decades; after that they slowly begin to decline with respect to their overall health and wellbeing. This is called senescence. Some people begin the stage of senescence earlier than others. Some adults are vigorous into their eighth and ninth decade of life while others are already senescent in their sixth decade. There are tremendous individual differences that in part are attributable to genetics and in part due to lifestyle choices and environmental effects.
