Arteriovenous distribution of hemodynamic parameters in the rat dental pulp

A systematic investigation of the distribution of red cell velocity throughout the hierachy of the rat pulp microvascular network was performed. Luminal diameters (D) of microvessels ranging in size from 8 to 72 micron were measured in situ by an electronic video image shearing technique. Intravascular red cell velocities (Vrbc) were simultaneously measured by a variation of the "two-slit" photometric technique and intravascular volumetric flow rates (Q) were calculated. It was found that red cell velocity decreased monotonically throughout successive arteriolar divisions to attain capillary values of 1/10 those in the feeding arterioles. A slight rise in Vrbc was found in the venous confluences, however, a maximum value of Vrbc of only 1/5 large arteriolar values was evident in the large collecting venules. In contrast, the calculated volumetric flow rate distribution was found to be nearly parabolic from arterioles (40 micron) and their paired (72 micron) collecting venules. This behavior was attributed to the dominance of microvessel cross-sectional areas as a determinant of Q.