Cardiovascular System: Vessels Chapter 20 – Lecture Notes

1. Cardiovascular System: VesselsChapter 20 – Lecture Notes to accompany Anatomy and Physiology: From Science to Life textbook by Gail Jenkins, Christopher Kemnitz, Gerard Tortora

2. Chapter Overview 20.1 Arterial Blood Flow Overview 20.2 Capillaries 20.3 Venules and Veins 20.4 Capillary Exchange 20.5 Blood Flow 20.6 Blood Pressure Regulation 20.7 Pulse 20.8 Systemic and Pulmonary Circuits

3. Essential Terms artery • blood vessel carrying blood away from the heart vein • vessel carrying blood toward the heart capillaries • smallest vessels that function in exchange of nutrients and wastes between blood and body cells

4. Introduction • Blood vessels transport materials throughout body • carry nutrients to cells • carry wastes away for excretion • From heart to • arteries to • arterioles to • capillaries to • venules to • veins to heart

5. Concept 20.1Arteries

6. Arteries • Two main types • elastic arteries • muscular arteries • Three coats • tunic interna • endothelium, basement membrane, internal elastic lamina • tunica media • elastic fibers and smooth muscle fibers • tunic externa • elastic and collagen fibers • Innervated by sympathetic fibers of ANS

7. Figure 20.1ab

8. Figure 20.1c

9. Figure 20.1d

10. Figure 20.1e

11. Elastic Arteries • largest diameter • highest proportion of elastic fibers in tunica media • help propel blood onward while ventricles are relaxing • stretch with surge of blood • recoil when pressure decreases

12. Figure 20.2

13. Muscular Arteries • medium-sized arteries • tunica media has more smooth muscle and fewer elastic fibers than elastic arteries • adjust blood flow • capable of greater vasoconstriction and vasodilation • most named arteries are muscular arteries

14. Arterioles • muscular arteries divide into smaller arteries • smaller arteries divide into arterioles • arterioles feed capillaries • tunics minimize as they near capillary beds • regulate resistance • contraction of smooth muscle increases resistance • can significantly affect blood pressure

15. Figure 20.3

16. Concept 20.2Capillaries

17. Capillaries • microscopic vessels that connect arterioles to venules • exchange vessels • fed by metarterioles • found near almost every cell in the body • number varies with metabolic activity of tissue they serve • center vessel is thoroughfare channel • all others have precappillary sphincters that can constrict and restrict flow

18. Figure 20.3

19. Three Capillary Types From least leaky to most leaky • continuous • fenestrated • sinusoids If blood passes from one capillary network to another through a vein • vein is called portal vein • second network is called portal system

20. Figure 20.4a

21. Figure 20.4b

22. Figure 20.4c

23. Concept 20.3Venules and Veins

24. Venules • capillaries unite to form venules • drain into veins • tunica interna and tunica media

25. Veins • venules unite to form veins • return blood to the heart • tunica interna, media, and externa • thinner than arteries • many have valves to prevent back flow • low pressure system

26. Figure 20.5

27. Veins • venules unite to form veins • return blood to the heart • tunica interna, media, and externa • thinner than arteries • many have valves to prevent back flow • low pressure system

28. Table 20.1

29. Blood Reservoirs • about 64% of blood is in systemic veins and venules at any given moment • brain stem can vasoconstrict these vessels allowing greater blood flow to skeletal muscles

30. Figure 20.6

31. Concept 20.4Capillary Exchange

32. Capillary Exchange • exchange mechanisms include • diffusion • transcytosis • bulk flow • Hydrostatic pressure influences exchange • Blood colloid osmotic pressures helps blood retain fluid in vessels • resisted by interstitial fluid osmotic pressure

33. Figure 20.7

34. Filtration and Reabsorption • filtration • pressure driven movement of fluid and solutes FROM blood into interstitial fluid • reabsorption • pressure driven from interstitial fluid INTO blood vessels • net filtration pressure (NFP) • difference between filtration pressure and reabsorption pressure is

35. Figure 20.7

36. Concept 20.5Blood Flow

37. Blood Pressure • hydrostatic pressure exerted by blood on walls of blood vessel • measured in mm Hg • systolic blood pressure • highest pressure attained in arteries during systole • diastolic blood pressure • lowest pressure during diastole • mean arterial pressure • average of systolic and diastolic pressures • useful when considering blood flow

38. Figure 20.8

39. Vascular Resistance • opposition to blood flow due to friction between blood and walls of vessels • increase in resistance increases BP • decrease in resistance decreases BP • Systemic vascular resistance depends on three things • size of lumen • larger lumen less resistance • blood viscosity • thinner blood less resistance • vessel length • shorter length less resistance

40. Venous Return • mechanisms that “pump” blood from lower body to heart • skeletal muscle pump • figure 20.9 • respiratory pump • during inhalation the diaphragm moves downward increasing pressure in abdominal cavity and decreasing pressure in thoracic cavity • abdominal veins are compressed and blood forced upward

41. Figure 20.9

42. Velocity of Blood Flow • Inversely related to cross-sectional area of vessel • slowest where area is greatest • velocity slows as blood moves into larger veins • Circulation time • time required for a drop of blood to pass from right atrium through pulmonary and systemic circulation back to right atrium • normally about 1 minute

43. Figure 20.10

44. Concept 20.6Blood Pressure Regulation

45. Cardiovascular Center • in medulla oblongata • controls neural and hormonal negative feedback systems • input • from cerebral cortex, limbic system and hypothalamus • sensory receptors • proprioceptors, baroreceptors, chemoreceptors • output • ANS sympathetic & parasympathetic neurons • vasomotor nerves throughout body • especially skin and abdominal visceral

46. Figure 20.11

47. Neural Regulation of BP • Baroreceptor Reflexes • pressure sensitive sensory receptors in • aorta, internal carotid arteries in neck and chest • two most important • carotid sinus reflex (BP in brain) • aortic reflex (BP in ascending arch of aorta) • if pressure drops • sympathetic stimulation increases • parasympathetic stimulation decreases • Chemoreceptor Reflexes • monitor carbon dioxide, oxygen gas, pH

48. Figure 20.12

49. Figure 20.13

50. Hormonal Regulation of BP • Renin-angiotensin-aldosterone system • endocrine response • Epinephrine and norepinephrine • sympathetic nervous system • ADH • ANP