Fractality: An Adaptive Evolutionary Conserved Bioengineering Design of the Gas Exchangers

In biology, termed ‘Bauplans’ (body plans), ‘ground plans’ and ‘blue-prints’, fractality is a noteworthy evolutionary extensively conserved morphological feature. Particularly in the last six decades, fractal geometry (FG) has advanced from a mere intellectual concept to a branch of applied mathematics of considerable heuristic value and important practical application in as diverse fields as engineering, architecture, medicine and social sciences. FG meaningfully explicates morphological- and physiological states and processes. In medicine, it quantitatively characterizes abnormalities, pathologies and diseases. Here, we show that across animal taxa, structurally, gas exchangers are inherently fractal. Whilst providing optimal flow conditions of the respiratory fluid media (RFM) (air/water and blood), branching morphology optimizes respiratory surface area. For the lungs, tight patterning and proximation of the functional parts brings the RFM close, enhancing gas exchange by passive diffusion. Except for the lung, brain, blood vessels, kidney and nervous system, few organs and tissues have been morphologically analyzed to the extent of determining their fractal dimensions. Such detailed studies are urgently required. They should instructively inform on why and how diseases and pathologies affect some organs and tissues and not others. Furthermore, biomimetically, they may instruct on the most effective ways of designing efficacious artificial supporting devices.