Blood movement in the circulatory system

Estimated from the average annual streamflow (5 x 10 ft /s according to U.S. Geological Survey records) and the average width and depth near Clinton, IA (500 and 5 m, respectively). 

Flow through the vessels of the circulatory system is driven by the hydrostatic pressure created in the ventricles. The flow rate through a cyhndrical vessel of radius R can be estimated from the equations for conservation of momentum (see [4])  

Without valves, the relaxation-contraction cycle of the ventricle would produce no net forward flow, but an endless repetition of blood ejection during the contraction phase and blood return during the relaxation phase. 

This equation can be simplified by the following assumptions (which apply reasonably well to blood flows in most vessels in humans)  

Equation 6-5 can be integrated over the vessel cross-section to obtain an overall rate of blood flow  

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