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Overview of Circulation Blood pressure, Flow and Resistance

Overview of Circulation Blood pressure, Flow and Resistance. Generalized Structure of Blood Vessels. Functional Parts of the Circulation. Arteries: their function is to transport blood under high pressure to the tissues. They strong vascular walls.

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Overview of Circulation Blood pressure, Flow and Resistance

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  1. Overview of Circulation Blood pressure, Flow and Resistance

  2. Generalized Structure of Blood Vessels

  3. Functional Parts of the Circulation • Arteries: their function is to transport blood under high pressure to the tissues. They strong vascular walls. • Arterioles are the last small branches of the arterial system. They act as control conduits through which blood is released into the capillaries. • Function of capillariesis to exchange fluid, nutrients, electrolytes and hormones, and other substances between the blood and interstitial fluid. • Venules collect blood from capillaries, and join into larger veins. • Veins function as conduits for transport of blood from the venules back to the heart. Also major reservoir of extra blood.

  4. Distribution and Volumes of Blood in Different Parts of the Circulatory System

  5. Capillary Beds

  6. Volumes of Blood in Different Parts of the Circulation • About 84% of the blood volume is in the systemic circulation • 16% in the heart and lungs • Of the 84% in the systemic circulation, 64% is in the veins, 13% in the arteries and 7% in the systemic arteries and capillaries. • The heart contains 7% of the blood • Pulmonary vessels in the lungs contain 9% of the blood

  7. Systemic Blood Pressure

  8. Pressures in Various Parts of the Circulation

  9. Basics of Circulatory Function 1) The rate of blood flow to each tissue is almost always precisely controlled in relation to the tissue need. 2) The cardiac output is controlled mainly by the sum of all the local tissue flows (role of venous return) 3) In general, the arterial pressure is controlled independently of either local blood flow control or cardiac output control. • In summary, needs of the individual tissues are served specifically by the circulation.

  10. Types of Blood Flow • Laminar flow of blood in vessels: when blood flows at a steady rate through a long, smooth blood vessel, it flows in streamlines. • Turbulent flow of blood under some conditions: Blood flowing in all directions, continually mixing within the vessel.

  11. Blood Pressure • Blood pressure (BP) means the force exerted by the blood against any unit of the vessel wall. • BP is measured in millimeters of mercury (mmHg)

  12. Cardiac Cycle and Blood Pressure http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__the_cardiac_cycle__quiz_2_.html http://health.howstuffworks.com/adam-200079.htm

  13. Measuring BP by invasive methods, using electronic transducers

  14. Resistance to Blood Flow • Resistance is the impediment to blood flow in a vessel • It cannot be measured directly • Instead, resistance can be calculated from measurements of blood flow and pressure difference between two points in the vessel. • Resistance of the entire systemic circulation is called total peripheral resistance (TPR) • TPR is equal to the sum of resistances of the arteries, arterioles, capillaries, venules and veins.

  15. Diameter of Vessels and Blood Flow • Very slight changes in diameter of a vessel can change its conductance tremendously

  16. Effect of Hematocrit and Blood Viscosity on Vascular Resistance and Blood Flow • The greater the viscosity, the less the flow in a vessel if all other factors are constant. • Viscosity of normal blood is about three times as great as the viscosity of water. • Hematocrit: The percentage of the blood cells to plasma. • Hematocrit of men averages about 42 • Hematocrit of women averages about 38

  17. Effects of anemia or polycythemia…

  18. Effect of Hematocrite on Blood Viscosity

  19. Effects of pressure on vascular resistance and tissue blood flow

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