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Cardiovascular System: Circulation Pathways and BP Regulation. Anatomy & Physiology II Tony Serino, Ph.D. Biology Department Misericordia University. Blood Vessels. Arteries –conduct blood away from heart Elastic arteries, Muscular arteries, arterioles Veins –conduct blood toward heart
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Cardiovascular System: Circulation Pathways and BP Regulation Anatomy & Physiology II Tony Serino, Ph.D. Biology Department Misericordia University
Blood Vessels • Arteries –conduct blood away from heart • Elastic arteries, Muscular arteries, arterioles • Veins –conduct blood toward heart • Venules, small and large veins • Capillaries –thinnest blood vessel; used in exchange, is the functional unit of circulatory system (Microcirculation) • AV shunts, metarterioles, pre-capillary sphincters, and capillary bed
Capillary Anatomy Three types: tight, fenestrated and sinusoids
Capillary Types Tight Capillary Fenestrated Capillary Sinusoidal Capillary
Arteries and Veins • Arteries are known as resistance vessels, especially the arterioles • Arteries withstand the greatest BP • Veins are capacitance vessels, they are able to change the diameter to hold more or less blood
Artery Anatomy (CT) (Smooth Muscle) (Controlled by sympathetic system = vasomotor nerves)
BP through Vascular Tree Small changes in arteriolar diameter produce big changes in resistance; termed total peripheral resistance (TPR)
TPR (total peripheral resistance) • TPR is the opposition to blood flow through the vessel (caused by friction) • Arteries with their smaller lumen resist blood flow • Arteriolar diameter contribute the most to TPR • Arteriolar compliance (the ability of the vessel to distend) controls the TPR • Sympathetic innervation controls arteriolar radius • The viscosity of the blood also affects resistance
Blood flow in a healthy system is Laminar (smooth –no sound) Blood flow in a unhealthy system is Turbulent (rough –noisy)
Factors Affecting CO (Review) Starling Forces
Blood Pressure • BP = SP/DP • Systolic Pressure (SP) –the pressure in the artery during systole • Diastolic Pressure (DP) –the pressure in the artery during diastole • Mean Arterial Pressure (MAP) (weighted average)MAP = DP + 1/3 (PP) • Pulse Pressure (PP) = SP - DP • MAP = CO x TPR
SP DP