The input impedance of an assembly of randomly branching elastic tubes.

Computations are presented of the input impedance of assemblies of randomly bifurcating elastic tubes, as a generalized model of the arterial system. Account is taken of the viscosity of the fluid, the viscoelastic properties of the walls, the variation of elasticity in the different orders of branches, and the variation in cross-sectional area at the bifurcations. The results show that the distributed and scattered nature of the terminations of such an assembly greatly reduces the influence of reflections upon the behavior of the input impedance. The variation of impedance with frequency is very similar in form to that found in animal experiments for the input impedance of the aorta. The architecture of the arterial system may thus be considered to play an important part in determining the favorably low impedance presented to the heart by the aorta.