As the result of this pattern, total cross-sectional area increases progressively from aorta to capillary (See Figure 7.03). This dictates that blood flow velocity must decrease sharply between the aorta and the capillaries, since all the components are in series and the entire blood volume must pass through all the components. This also dictates that blood flow velocity must increase again in flowing from the capillaries to the vena cava. In fact, flow velocity in the vena cava is about 75% that in the aorta. Thus, there is a reciprocal relationship in the circulation between total cross-sectional area and flow velocity.
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