Microvascular Hemodynamics in the Chick Chorioallantoic Membrane (CAM)

Abstract

Theoretical modeling techniques were employed to investigate the hemodynamic coupling between arterioles, capillaries and venules in the developing microcirculation of the chorioallantoic membrane (CAM) of the chick embryo, based on structural and hemodynamic experimental observations. The microvasculature of the CAM is characterized by interdigitating arteriolar and venular trees, both of which are linked to a mesh-like capillary plexus. A day-14 CAM network with an area of about 1 cm2 was imaged and digitally reconstructed, providing information about vessel length, diameter, and 3D location of over 7000 vessel segments. Since the capillary plexus structure was not resolved by imaging, it was modeled as a porous medium. The supply of blood from the arterioles to the capillaries and drainage into the venules were represented by distributions of point sources and sinks of flow. Predicted flow velocities were compared with blood velocity measurements in arterioles and venules with diameters 16 to 100 µm, obtained in the CAM via video microscopy. If it was assumed that blood flows into the capillary plexus only at the ends of terminal arterioles, the predicted velocities increased with decreasing diameter in vessels <50 µm in diameter, contrary to the observations. Distributing sources or sinks at 50 µm intervals along arterioles and venules led to velocities consistent with the data. The results imply that vascular connections to the capillary plexus must be present along the length of the arterioles and venules, not only at the ends of terminal arterioles and venules. This research was supported by NIH HL034555 and HL070657.