The Arterial and Venous Systems

1. The Arterial and Venous Systems

3. Vasculature

4. Diagram of Vasculature

5. Systemic Circulation

6. Blood Vessels

10. The Arterial System

11. The Arterial System Function of the arterial system is to distribute blood to the capillary systems in the body The arterioles regulate the distribution of flow of blood to the various capillary beds (�stopcocks� of the vascular system)

12. Pressure along the entirecardiovascular circuit

13. Arterial Blood Pressure

14. Blood Pressure Pulse Pressure = Systolic BP - Diastolic BP Mean Arterial Pressure

15. CalculatingMean Arterial Pressure

16. The pressure curves change in arteries at different distances from the heart

17. The pressure curves change in arteries at different distances from the heart Delay in onset of initial pressure rise Three major changes: The high-frequency components of the pulse, such as the incisura, are damped out and soon disappear The systolic portions of the pressure wave become narrowed and elevated A hump may appear on the diastolic portion of the pressure wave

18. The pressure curves change in arteries at different distances from the heart

19. The Arterial System ConvertsPulsatile Bloodflow toContinuous Bloodflow

20. Arterial System Hydraulic Filter Composed of elastic conduits (aorta and arteries) and high-resistance terminals (arterioles) Hydraulic filtering converts the intermittent output of the heart to a steady flow in the capillaries This minimizes the workload of the heart, i.e., more work is required to pump a given flow intermittently as compared to steadily

21. Arterial System Part of the energy of cardiac contraction is dissipated as forward capillary flow during systole (kinetic energy) The remainder is stored as potential energy, in that much of the stroke volume is retained by stretching the distensible arteries During diastole the elastic recoil of the arterial walls converts this potential energy into capillary blood flow

22. Arterial System If vessels were rigid:� ALL the blood the heart pumped would be immediately converted to flow During diastole, there would be no flow (including no flow to capillaries) Pumping blood through rigid vessels creates much more work for heart Bottom line: elastic arteries ensure constant flow through capillaries and reduce work of pumping

23. Conversion of Intermittent Bloodflow to Continuous Bloodflow

24. Factors Determining Aortic Pulse Pressure Pulse pressure = Systolic pressure � Diastolic pressure

25. Factors Determining Aortic Pulse Pressure

26. Arterial Compliance

27. Arterial Compliance

28. Arterial Compliance In general, our arteries get stiffer as we get older, i.e., they become less compliant. This is primarily due to loss of elastic tissue.

29. Factors That Determine Mean Arterial Pressure

30. Mean Arterial Pressure Ohm�s Law: Q = ?P/R CO = (MAP-CVP)/SVR SVR = (MAP-CVP)/CO MAP = (CO x SVR) + CVP

31. Relationship Between:CO, SVR, MAP, and CVP

33. Venous System

34. Function of Veins Reservoir for the cardiovascular system 70% of the blood volume may be stored in the veins Venous pump helps propel blood forward Enhances venous return

35. Volume-Pressure Curves of the Arterial and Venous Circulations

36. Central Venous Pressure Central Venous Pressure Blood pressure in the thoracic vena cava near the right atrium It determines the filling pressure of the right ventricle CVP is regulated by: A balance of the heart to pump blood out of the right atrium and right ventricle into the lungs The tendency for blood to flow from the peripheral veins to the right atrium (venous return)

37. Factors That Increase CVP Decreased Cardiac Output Increase in Total Blood Volume Venous Constriction Gravity Standing to supine position Arterial Dilation Respiratory Activity Increased rate and rate of respiration Skeletal Muscle Pump Exercise

38. Effect of Gravitational Pressure on Venous Pressure Pressure rises 1 mm-Hg for each 13.6 mm distance below the surface of a body of water In a standing person the pressure in the veins may be: Feet = 90 mm-Hg Sagittal sinus = -10 mm-Hg

39. Effect of Gravitational Pressure on Venous Pressure

40. Effects of Gravity on the Venous System and Cardiac Output Gravity Venous pooling may significantly reduce CO

41. Effects of Respiration Spontaneous respiration Decreased intra-thoracic pressure results in a decreased right atrial pressure which enhances venous return Mechanical ventilation Increased intra-thoracic pressure during positive-pressure lung inflation causes increased right atrial pressure which decreases venous return Valsalva Maneuver Causes a large increase in intra-thoracic pressure which impedes venous return to the right atrium

42. Muscular Activity and the "Venous Pump"

43. Blood Reservoir Function of the Veins Specific Reservoirs Spleen Liver Large abdominal veins Venous plexus beneath the skin Non-venous Blood Reservoirs Heart Lungs