A biomechanical model of the skeletal muscle microcirculation with pulsatile pressure and myogenic response

The microcirculation in the skeletal muscle is controlled by several local regulatory mechanisms in which the myogenic response plays an important role. The objective of this dissertation is to develop a biomechanical model for the myogenic response with consideration of pulsatile pressure-flow relationship.;Two basic assumptions are made to formulate the myogenic contraction: (1) the arterioles maintain its viscoelastic properties during active myogenic vasoconstriction; (2) the active myogenic vasoconstriction or dilatation is the result of a change in reference diameter of the vessel.;The model was initially tested for pressure and diameter responses with experimental results in the literature. Good agreement is shown with a wide spectrum of in vitro and in vivo observations.;A sequence of the in vivo experiments was performed on arterioles in the rat cremaster muscle. A modified "box method", in which the tissue was enclosed in a sealed chamber, was used to change extravascular pressure in order to stimulate the myogenic response. Model parameters were measured, and then the theoretical predictions were compared with experiments for ramp or oscillatory pressure histories. The results further confirmed the theory and show a trend for a stronger myogenic response in the transverse than in the arcade arterioles.;A theoretical analysis is presented with the developed myogenic model and time variant pressure and flow. Finite element and finite difference algorithm were applied to solve the nonlinear PDE governing microvascular pressure and flow. The results indicate that the myogenic response and the viscoelasticity of the microvessels are important in the phenomena such as blood flow autoregulation, reactive hyperemia and zero flow pressure.