Chapter+14+blood+vessels - Chapter 14:Blood Vessels, Flow...

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Unformatted text preview: Chapter 14:Blood Vessels, Flow & Pressure Flow Rule – Circulatory system = closed system – Pressure = force exerted by blood – Flow occurs from high pressure to low pressure Blood Vessels • Arteries – relatively large, branching vessels that conduct blood away from the heart • • Arterioles – small branching vessels with high resistance • • Capillaries – site of exchange between blood & tissue • Venules – small converging vessels; have valves • • Veins – relatively large converging vessels that conduct blood to the heart • Closed system Heart arteries arrioles capillaries venules veins back to heart Pressure Gradients in the Cardiovascular System – Pressure gradients drive flow from high pressure to low pressure – Flow due to pressure gradients = bulk flow – Heart creates pressure gradient for bulk flow of blood – A gradient must exist throughout circulatory system to maintain blood flow Pressure Gradient Across Systemic Circuit – Pressure gradient = pressure in Aorta minus pressure in central venous just before it empties into right atrium – Pressure in aorta = mean arterial pressure (MAP) = 90 mm Hg – Pressure in vena cava = central venous pressure (CVP) = 0 mHg – Pressure gradient = MAP – CVP = 90mmHg – Figure 14.2 Pressures and Pressure Drops in the Pulmonary and Systemic Circuits 14.3 drop in systemic vs pulmonary why???? 14.3 Resistance in the Cardiovascular System – Pressure gradient in systemic circuit much greater than for pulmonary circuit – Flow through both circuits equal – Flow = deltaP/R resistance in pulmonary is much less ? why???) – Resistance through pulmonary circuit much Factors Affecting Resistance to Flow : figure 14.4 – Radius of vessel – In arterioles (and small arteries) - can regulate radius regulate flow – Length of vessel – Viscosity of fluid = η – Blood viscosity dependent on amount of RBCs and proteins – Regulate Blood Flow by Regulating Radius • Regulation of radius of arterioles (and small arteries) – Vasoconstriction – Decrease readius increase resisitance – Vasodilation Increases radius decrease resistance vasodialator used for hypertension • Pulmonary circuit less resistance than systemic – lower pressure gradient required for blood flow – Relating Pressure Gradients and Resistance in the Systemic Circulation – Flow = cardiac output=CO – deltaP= mean arterial pressure= MAP (co=MAP/TPR) – R = total peripheral resistance =TPR, what causes resistance? – Overview of the Vasculature – Arteries – carry blood away from heart – Microcirculation – Arterioles – Capillaries – site of exchange – Venules – Veins – return blood to heart Blood Vessels • Elastic arteries: – Walls of smooth muscle and elastin....
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This note was uploaded on 04/08/2008 for the course BIOL 2160 taught by Professor Kt during the Spring '08 term at LSU.

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Chapter+14+blood+vessels - Chapter 14:Blood Vessels, Flow...

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