Page 2, Architecture of the Circulation, Dr. D. Penney


Functional Components:

Regardless of the differences, the systemic and pulmonary circulations have similar functional components (Figure 7.01). First there is a discontinuous pump, the left ventricle and right ventricle, respectively, which propel the blood into the great vessels in a pulsatile fashion. They differ, of course, in that maximum left ventricle pressure is 4-5 fold that of the right ventricle. Tissues and organs do better when perfused by pulsatile as opposed to continuous flow.

Blood is received from each pump by the windkessel (German for wind-kettle) vessels, the aorta and pulmonary artery, whose walls passively stretch, storing pressure energy. This energy is given back during diastole, supporting arterial blood pressure at this time, serving to dampen the pulse wave, and to facilitate flow. This principle was first recognized in the last century by the famous German physiologist, Ernest Weber, who realized that in this respect the circulation was like the pumping mechanism of the fire trucks of that period. With perfect hydraulic filtering (pressure dampening), the work done by a pulsatile pump is the same as that done by a continuous pump.

Thus the major function of these large arteries is pressure storage and bulk flow. Hydraulic filtering is more nearly perfect for the left ventricle than for the right ventricle.




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