Ageing is a multi-causal process with some ageing mechanisms being more predominant in some tissues than in others. This is due to the difference in the biological make-up of tissues which makes them more or less predisposed to a particular ageing mechanism. Since tissues are normally composed of a mixture of mitotic cells, post-mitotic cells and long-lived proteins that are functionally inter-related, there is going to be considerable overlap in the ageing mechanism within tissues. An alteration in one tissue component will likely have a direct impact on another. The outcome of such changes is going to be different from tissue to tissue due to impairment of specific structure-function relationships.