Distribution of vascular resistance in terminal arteriolar networks of cat sartorius muscle.

Morphometric information on the terminal arteriolar networks (n = 10) in cat sartorius muscle [Koller et al., Am. J. Physiol. 253 (Heart Circ. Physiol. 22): H154-H164, 1987] is utilized in the calculations of distribution of vascular hindrance throughout the networks. These networks have tree-type geometry, i.e., they do not contain closed loops. The results are discussed in terms of simulated flow distribution. The flow calculations are based on the exact geometry of the arteriolar networks (the control and dilated diameter and the length of each vascular segment) and on assumed values of postarteriolar resistances. Three cases of postarteriolar resistances are considered: zero, constant, and randomly distributed. With zero postarteriolar resistances, the distribution of flow in the terminal arteriolar segments would be highly heterogenous. The simulated flow in each terminal segment is determined primarily by the number of bifurcations on the pathway leading to the terminal segment, with a slight compensation for the length of the pathways. The coefficient of variation of flow in the control state, CV(Qc), would be close to the value in the dilated state, CV(Qd). When each of the terminal segments is connected to a constant postarteriolar resistance, the CV's in both states decrease. The coefficient of variation in the dilated state becomes significantly smaller than in the control state. When postarteriolar resistances are randomly distributed, both CV's increase, and their values become closer to each other. These results suggest that postarteriolar resistances may play a very important role in distribution of flow in the microvascular network. This study formulates a framework for the quantification of the effect of arteriolar dilation on flow redistribution in the network.