Physiology 3120 Lecture Notes - Lecture 6: Pulmonary Artery, Pulmonary Circulation, Vascular Resistance
12 Jan 2017
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Document Summary
Two circulatory systems: pulmonary circulation, systemic circulation the arterial system become smaller and smaller. Cross sectional area and velocity of blood flow. Proliferation of more and more blood vessels leads to a massive increase in total cross section area. Consecutive branches of i. e. capillaries have the smallest cross- sectional area but many capillary beds so total cross sectional area is massive: vena cava > aorta. The same total blood flow (l/min) passes each level: 5 l/min passes through all bvs. Where blood velocity is slowest: greatest sa. Aorta and large arteries: arteries are very compliant, thin walls that can expant & accommodate blood volume, very little resistance to blood flow so pressure remains high. Small arteries: less compliant, fall in pressure begins where the resistance to flow begins to increase. Arterioles: not compliant at all, the greatest resistance to flow accounting for about half the resistance in the entire systemic circulation. Capillaries: the pressure drop is ~20 mmhg.
