[Structural and functional organization of the microcirculatory bed of the frog and rat mesentery]

The arteriolar and venular network and the blood flow distribution were studied in mesenteric microvascular beds of frogs and rats. Some principles of spatial organization were established: an increase of branching coefficient, a decrease of branching asymmetry with the internal diameter of parent vessel progressively diminishing, the more frequent branching of venous tree including the fragment of a relatively greater volume. The values of geometrical and hemodynamical parameters were different in frogs and rats. Experimental dependence between pressure gradients and vessel radii was found to be exponential, thus being in agreement with prediction of a mathematical model based on physiologically significant criteria.