BIOC63H3 Lecture Notes - Lecture 9: Blood Pressure, Cardiac Output, Stroke Volume
Document Summary
The venules and veins return the blood from the microcirculation to the right atrium of the heart. They do not, however, serve merely as passive conduits. Instead, they have a crucial active role in stabilizing and regulating the venous return of blood to the heart. The venous system differs from the arterial system in two important respects. First, the total volume (and cross-sectional area) of the venous system is much greater that that if the arterial system. This is because there are many more venules than arterioles; venules also tend to have larger internal diameters than arterioles. Second, the veins are quite thin walled, and can therefore expand greatly to hold more blood if their internal pressure rises. As a result of its large cross-sectional area, the venous system offers much less resistance to flow compared to the arterial system.
