Veins

1. Veins • Collect blood from all tissues and organs and return it to the heart • Are classified according to size • Venules • Medium-sized veins • Large veins

2. Arterial blood pressure • Arterial blood pressure • Maintains blood flow through capillary beds • Rises during ventricular systole and falls during ventricular diastole • Pulse is a rhythmic pressure oscillation that accompanies each heartbeat • Pulse pressure = difference between systolic and diastolic pressures Mean arterial pressure (MAP)

3. Figure 21.10 Pressures within the Cardiovascular System Figure 21.10

4. Figure 21.10 Pressures within the Cardiovascular System Figure 21.10

5. Capillary Exchange • Flow of water and solutes from capillaries to interstitial space • Plasma and interstitial fluid are in constant communication • Assists in the transport of lipids and tissue proteins • Accelerates the distribution of nutrients • Carries toxins and other chemical stimuli to lymphoid tissues

6. Processes that move fluids across capillary walls • Diffusion • Filtration • Hydrostatic pressure (CHP) • Reabsorption

7. Figure 21.12 Capillary Filtration Figure 21.12

8. Figure 21.12 Capillary Filtration Figure 21.12

9. Forces acting across capillary walls • Capillary hydrostatic pressure (CHP) • Blood colloid osmotic pressure (BCOP) • Interstitial fluid colloid osmotic pressure (ICOP) • Interstitial fluid hydrostatic pressure (IHP)

10. Filtration and reabsorption • Processes involved in filtration and reabsorption include • Net hydrostatic pressure • CHP - IHP • Net colloid osmotic pressure • BCOP - ICOP

11. Figure 21.13 Forces Acting across Capillary Walls Figure 21.13

12. Venous pressure and venous return • Assisted by two processes • Muscular compression • The respiratory pump PLAY Animation: Factors that Affect Blood Pressure

13. SECTION 21-3Cardiovascular Regulation

14. Cardiovascular Regulation • Autoregulation • Neural mechanisms • Endocrine mechanisms

15. Autoregulation of blood flow within tissues • Local vasodilators accelerate blood flow in response to: • Decreased tissue O2 levels or increased CO2 levels • Generation of lactic acid • Release of nitric acid • Rising K+ or H+ concentrations in interstitial fluid • Local inflammation • Elevated temperature

16. Figure 21.14 Homeostatic Adjustments that Compensate for a Reduction in Blood Pressure and Blood Flow Figure 21.14

17. Figure 21.14 Homeostatic Adjustments that Compensate for a Reduction in Blood Pressure and Blood Flow Figure 21.14

18. Neural Mechanisms • Adjust CO and PR to maintain vital organ blood flow • Medullary centers of regulatory activity include • Cardiac centers • Vasomotor centers control • Vasoconstriction via adrenergic release of NE • Vasodilation via direct or indirect release of NO

19. Reflex control of cardiovascular function • Baroreceptors reflexes monitor stretch • Atrial baroreceptors monitor blood pressure • Chemoreceptor reflexes monitor CO2, O2, or pH levels PLAY Animation: Autoregulation and Capillary Dynamics

20. Figure 21.15 Baroreceptor Reflexes of the Carotid and Aortic Sinuses Figure 21.15

21. Figure 21.16 The Chemoreceptor Reflexes Figure 21.16

22. Hormones and cardiovascular regulation • Antidiuretic hormone – released in response to decreased blood volume • Angiotensin II – released in response to a fall in blood pressure • Erythropoietin – released if BP falls or O2 levels are abnormally low • Natriuretic peptides – released in response to excessive right atrial stretch

23. Figure 21.17 The Regulation of Blood Pressure and Blood Volume Figure 21.17a

24. Figure 21.17 The Regulation of Blood Pressure and Blood Volume Figure 21.17b

25. Venous Valves • Venules and medium-sized veins contain valves • Prevent backflow of blood

26. Figure 21.6 The Function of Valves in the Venous System Figure 21.6

27. Distribution of blood • Total blood volume is unevenly distributed • Venoconstriction maintains blood volume • Veins are capacitance vessels • Capacitance = relationship between blood volume and pressure PLAY Animation: Anatomy Review: Blood Vessel Structure and Function

28. Figure 21.7 The Distribution of Blood in the Cardiovascular System Figure 21.7

29. SECTION 21-2Cardiovascular Physiology

30. Circulatory Pressure • Circulatory pressure is divided into three components • Blood pressure (BP) • Capillary hydrostatic pressure (CHP) • Venous pressure

31. Figure 21.8 An Overview of Cardiovascular Physiology Figure 21.8

32. Resistance (R) • Resistance of the cardiovascular system opposes the movement of blood • For blood to flow, the pressure gradient must overcome total peripheral resistance • Peripheral resistance (PR) is the resistance of the arterial system

33. Overview of Cardiovascular Pressures • Factors involved in cardiovascular pressures include • Vessel diameter • Cross-sectional area of vessels • Blood pressure • Blood viscosity

34. Figure 21.9 Relationships among Vessel Diameter, Cross-sectional Area, Blood Pressure, and Blood Viscosity Figure 21.9

35. SECTION 21-4Patterns of Cardiovascular Response

36. Exercise and the Cardiovascular System • Light exercise results in • Extensive vasodilation • Increased venous return • A rise in cardiac output • Heavy exercise results in • Increased blood flow to skeletal muscles • Restriction of blood flow to nonessential organs

37. Cardiovascular response to hemorrhaging: short term • Carotid and aortic reflexes increase CO and peripheral vasoconstriction • Sympathetic nervous system elevates blood pressure • E and NE increase cardiac output and ADH enhances vasoconstriction

38. Cardiovascular response to hemorrhaging: long term • Decline in capillary blood pressure recalls fluids from interstitial spaces • Aldosterone and ADH promote fluid retention • Increased thirst promotes water absorption across the digestive tract • Erythropoietin ultimately increases blood volume and improves O2 delivery

39. Figure 21.18 Cardiovascular Responses to Hemorrhaging and Blood Loss Figure 21.18