Physiological rules for the heart, lungs and other pressure-based organs

The structure of an organ system is matched to its functionality according to Taylor and Weibel’s theory of symmorphosis (1). This principle was defined as a biological system with economy of design and regulation at all levels. Since this principle is related to natural selection, it has been suggested that evolution may have played a major part in the mechanism of development of symmorphosis (2). As Calder had argued, symmorphosis can provide a theoretical basis for scaling relationships (3). Therefore allometry can be related to the pressures of natural selection, with optimization of efficiency of function leading to survival of the fittest, and the degree of symmorphosis can be tested by the degree of adherence to predicted allometric relationships (4)