Figure 1
From: Ill or just old? Towards a conceptual framework of the relation between ageing and disease
The biological mechanism underlying ageing The quadrangle (A) represents the human body. Extrinsic and intrinsic stressors cause injury (B). Subsequently, several mechanisms repair the injury, but the repair is not complete because of its high metabolic costs (C). As a consequence, damage accumulates (D-G), and cells, tissues, and organs decline in function.