ABSTRACT
This chapter describes the mechanisms of cellular deterioration and their relevance to organ and organismal function, along with implications for healthy ageing and successful treatment. An 'old cell' is one that has reached or is close to reaching the end of its replicative cycle - that is, is nearly or fully senescent. Even in the oldest individuals, most of the cells will not have reached this state and should still be considered young cells. Senescent cells accumulate with age in multiple organs and may therefore lead to deterioration through the autonomous depletion of functional cells. Cell senescence is clearly such a trait: it is beneficial as it prevents cells from becoming neoplastic; however, as senescent cells increase with age, the bystander effects become increasingly important in stimulating the malignancy of other cells, as well as contributing to organismal decline.
