Elastic Environment of the Capillary Bed

Abstract

To determine the degree to which the capillary blood vessels in vivo are supported by the elasticity of the surrounding tissue, a study was made of the elastic properties of the mesentery of the rabbit. A torsion test was made on a circular membrane of the avascular region of the mesentery, by applying a graded static torque and measuring the resulting deformation. The mesentery was found to have a modulus of rigidity in the same category as that of larger arteries and veins. It has a nonlinear stress-strain relationship with a tendency to harden at larger strains. In torsion experiments, the shear modulus G can be reduced to the following form G = µ+c₂|τ| Where c₂ is a constant and |τ| is the absolute value of the shear stress. The constant µ depends on the initial tension in the membrane. For the mesentery specimens, µ ranges from 215 to 1900 gm/cm², whereas the nondimensional constant c₂ has an average value of 8.23 with a standard deviation of 2.1. The hypothesis is advanced that the medium in which the capillaries of the mesentery are embedded is a gel and the capillary in effect is a tunnel in this gel. Such a hypothesis could explain the apparent rigidity of the blood capillaries.