 Dear students, in this topic we shall discuss the compliance in the circulatory system. You know that blood vessels have elastic fibers in them due to which they have the ability to distend. As pressure rises in them, the walls of the vessel distend, as a result the volume is increased. The ratio of change in volume with pressure is known as compliance of the system. The compliance of a system is related to its size and elasticity of its walls. Greater the initial volume and elasticity, greater is the compliance of the system. Dear students, the venous system is very compliant. That is, a small change in pressure produces large change in volume. Similarly, large change in volumes have little effect on venous pressure. Due to greater compliance of the venous system, it acts as a volume reservoir in the circulatory system. That is, volume change does not significantly change the blood pressure. Dear students, in comparison to the venous system, arterial system is less compliant. Due to this less compliance, arterial system acts as pressure reservoir. This is necessary for maintaining capillary blood flow. If the arterial system was more compliant, the result would be that when the diastole phase comes, the pressure would fall. But due to less compliance of the arterial system, the pressure remains maintained. And blood flow continues in the capillaries during the diastole. However, some portions of arterial system are more elastic and more compliant. For example, the portions of arteries near the heart. These compliance of arteries near the heart helps to reduce oscillations in pressure due to contractions of the heart. When heart muscles or ventricles contact, there are many changes in the pressure. This portion is compliant to minimize the effect of that change. It results in the maintenance of flow in distal arteries during diastole.