Chapter 21: Blood Vessels and Circulation Biol141 A P R.L. Brashear-Kaulfers

1. Chapter 21:Blood Vessels and CirculationBiol141 A & PR.L. Brashear-Kaulfers

3. The Largest Blood Vessels Attach to heart Pulmonary trunk: carries blood from right ventricle to pulmonary circulation Aorta: carries blood from left ventricle to systemic circulation

4. The Smallest Blood Vessels Capillaries Have small diameter and thin walls Chemicals and gases diffuse across walls

5. Structure of Vessel Walls

6. Arteries vs. Veins Arteries and veins run side-by-side Arteries have thicker walls and higher blood pressure Collapsed artery has small, round lumen Vein has a large, flat lumen Vein lining contracts, artery lining does not Artery lining folds Arteries more elastic Veins have valves

7. Arteries and Pressure Elasticity allows arteries to absorb pressure waves that come with each heartbeat Contractility -Arteries change diameter Controlled by sympathetic division of ANS

8. Vasoconstriction and Vasodilation Vasoconstriction -The contraction of arterial smooth muscle by the ANS Vasodilatation- The relaxation of arterial smooth muscle Enlarging the lumen Both Affect: afterload on heart peripheral blood pressure capillary blood flow

9. Structure of Blood Vessels

10. Arterioles Are small Have little or no tunica externa Have thin or incomplete tunica media

11. Artery Diameter Small muscular arteries and arterioles: changes with sympathetic or endocrine stimulation constricted arteries oppose blood flow Resistance (R) -The force opposing blood flow Resistance vessels: arterioles

12. Aneurysm A bulge in an arterial wall Is caused by weak spot in elastic fibers Pressure may rupture vessel

13. Capillaries Are smallest vessels with thin walls Microscopic capillary networks permeate all active tissues Capillary Function Location of all exchange functions of cardiovascular system Materials diffuse between blood and interstitial fluid

14. Capillary Structure

15. 2 Types of Capillaries 1. Continuous capillaries-Have complete endothelial lining Are found in all tissues except epithelia and cartilage Permit diffusion of: Water, small solutes, Lipid-soluble materials Block: blood cells, plasma proteins Are in CNS and thymus, Have very restricted permeability e.g., the blood�brain barrier 2. Fenestrated capillaries-Have complete endothelial lining Are found in all tissues except epithelia and cartilage, in choroid plexus, endocrine organs, kidneys,intestinal tract

16. Capillary Networks

17. Capillary Sphincter Guards entrance to each capillary Opens and closes, causing capillary blood to flow in pulses Vasomotion -Contraction and relaxation cycle of capillary sphincters Causes blood flow in capillary beds to constantly change routes

18. Veins Collect blood from capillaries in tissues and organs Return blood to heart Veins vs. Arteries Are larger in diameter Have thinner walls Carry lower blood pressure

19. 3 Vein Categories Venules: very small veins collect blood from capillaries Medium-sized veins: thin tunica media and few smooth muscle cells tunica externa with longitudinal bundles of elastic fibers Large veins: have all 3 tunica layers thick tunica externa thin tunica media

20. Valves in the Venous System

21. Blood Distribution

22. Venous Blood Distribution 1/3 of venous blood is in the large venous networks of the liver, bone marrow, and skin

23. Cardiovascular Physiology

24. Cardiovascular Regulation Maintains capillary blood flow in peripheral tissues and organs

25. Capillary Blood Flow Equals cardiac output Is determined by: pressure and resistance in the cardiovascular system

26. Measuring Pressure Blood pressure (BP): arterial pressure (mm Hg) Capillary hydrostatic pressure (CHP): pressure within the capillary beds Venous pressure: pressure in the venous system

27. Viscosity R caused by molecules and suspended materials in a liquid Whole blood viscosity is about 4 times that of water

28. Turbulence Swirling action that disturbs smooth flow of liquid Occurs in heart chambers and great vessels Atherosclerotic plaques cause abnormal turbulence

29. Pressures in the Systemic Circuit Systolic pressure: peak arterial pressure during ventricular systole Diastolic pressure: minimum arterial pressure during diastole Pulse pressure: difference between systolic pressure and diastolic pressure Mean arterial pressure (MAP): MAP = diastolic pressure + 1/3 pulse pressure

30. Abnormal Blood Pressure Hypertension: abnormally high blood pressure: greater than 140/90 Hypotension: abnormally low blood pressure

31. Venous Return Amount of blood arriving at right atrium each minute Determined by venous pressure Low effective pressure in venous system Low venous resistance Is assisted by: muscular compression of peripheral veins the respiratory pump Compression of skeletal muscles: pushes blood toward heart (one-way valves)

32. Capillary Exchange Vital to homeostasis Moves materials across capillary walls by: diffusion, filtration, and reabsorption

33. 5 Diffusion Routes Water, ions, and small molecules such as glucose: diffuse between adjacent endothelial cells or through fenestrated capillaries Some ions ( Na+, K+, Ca2+, Cl�): diffuse through channels in cell membranes Large, water-soluble compounds: pass through fenestrated capillaries Lipids and lipid-soluble materials such as O2 and CO2: diffuse through endothelial cell membranes Plasma proteins: cross endothelial lining in sinusoids

34. Capillary Filtration

35. Capillary Exchange At arterial end of capillary: fluid moves out of capillary into interstitial fluid At venous end of capillary: fluid moves into capillary out of interstitial fluid

36. The Transition Point Between filtration and reabsorption is closer to venous end than arterial end Capillaries filter more than reabsorb Excess fluid enters lymphatic vessels

37. 4 Functions of Blood and Lymph Cycle Ensures constant plasma and interstitial fluid communication Accelerates distribution of nutrients, hormones, and dissolves gases through tissues Transports insoluble lipids and tissue proteins that can�t cross capillary walls Flushes bacterial toxins and chemicals to immune system tissues

38. Capillary Dynamics Hemorrhaging: reduces CHP and NFP increases reabsorption of interstitial fluid (recall of fluids) Dehydration: increases BCOP accelerates reabsorption Increase in CHP or BCOP: fluid moves out of blood builds up in peripheral tissues (edema)

39. KEY CONCEPT Blood flow is the goal Total peripheral blood flow equals cardiac output Blood pressure overcomes friction and elastic forces to sustain blood flow If blood pressure is too low: vessels collapse, blood flow stops tissues die If blood pressure is too high: vessel walls stiffen, capillary beds may rupture

40. How do central and local control mechanisms interact to regulate blood flow and pressure in tissues?

41. Tissue Perfusion Blood flow through the tissues Carries O2 and nutrients to tissues and organs Carries CO2 and wastes away Is affected by: cardiac output peripheral resistance blood pressure

42. 3 Regulatory Mechanisms Control cardiac output and blood pressure: 1. Autoregulation: causes immediate, localized homeostatic adjustments Neural mechanisms: respond quickly to changes at specific sites 3. Endocrine mechanisms: direct long-term changes

43. Vasodilators Dilate precapillary sphincters Local vasodilators: accelerate blood flow at tissue level Low O2 or high CO2 levels Low pH (acids),Nitric oxide (NO) High K+ or H+ concentrations Chemicals released by inflammation (histamine) Elevated local temperature

44. Patterns of Cardiovascular Response Blood, heart, and cardiovascular system: work together as unit respond to physical and physiological changes (e.g., exercise, blood loss) to maintain homeostasis

45. Blood Distribution during Exercise

46. 3 Effects of Light Exercise Extensive vasodilation occurs: increasing circulation Venous return increases: with muscle contractions Cardiac output rises: due to rise in venous return (Frank�Starling principle) and atrial stretching

47. 5 Effects of Heavy Exercise Activates sympathetic nervous system Cardiac output increases to maximum: about 4 times resting level Restricts blood flow to �nonessential� organs (e.g., digestive system) Redirects blood flow to skeletal muscles, lungs, and heart Blood supply to brain is unaffected

48. Training and Cardiovascular Performance

49. Responses to Blood Loss

50. Responses to Severe Blood Loss Also called hemorrhaging Entire cardiovascular system adjusts to: maintain blood pressure restore blood volume To prevent drop in blood pressure: 1. carotid and aortic reflexes: increase cardiac output (increasing heart rate) cause peripheral vasoconstriction Sympathetic nervous system: triggers hypothalamus further constricts arterioles venoconstriction improves venous return

51. 3 Short-Term Responses to Hemorrhage To prevent drop in blood pressure: 1. carotid and aortic reflexes: increase cardiac output (increasing heart rate) cause peripheral vasoconstriction 2. Sympathetic nervous system: triggers hypothalamus further constricts arterioles venoconstriction improves venous return 3. Hormonal effects: increase cardiac output increase peripheral vasoconstriction (E, NE, ADH, angiotensin II)

52. Shock Short-term responses compensate up to 20% loss of blood volume Failure to restore blood pressure results in shock

53. 4 Long-Term Responses to Hemorrhage Restoration of blood volume can take several days: Recall of fluids from interstitial spaces 2. Aldosterone and ADH promote fluid retention and reabsorption 3. Thirst increases 4. Erythropoietin stimulates red blood cell production

54. What are the principle blood vessels and functional characteristics of the special circulation to the brain, heart, and lungs?

55. Blood Flow to the Brain Is top priority Brain has high oxygen demand When peripheral vessel constrict, cerebral vessels dilate, normalizing blood flow

56. Stroke Also called cerebrovascular accident (CVA) Blockage or rupture in a cerebral artery Stops blood flow

57. Blood Flow to the Heart Through coronary arteries Oxygen demand increases with activity Lactic acid and low O2 levels: dilate coronary vessels increase coronary blood flow Epinephrine: dilates coronary vessels increases heart rate strengthens contractions

58. Heart Attack A blockage of coronary blood flow Can cause: angina tissue damage heart failure death

59. Blood Flow to the Lungs Regulated by O2 levels in alveoli High O2 content: vessels dilate Low O2 content: vessels constrict Pulmonary Blood Pressure : In pulmonary capillaries: is low to encourage reabsorption If capillary pressure rises: pulmonary edema occurs

60. Circulation Patterns

61. The Pulmonary Circuit

62. The Pulmonary Circuit Deoxygenated blood arrives at heart from systemic circuit: passes through right atrium and ventricle enters pulmonary trunk At the lungs: CO2 is removed O2 is added Oxygenated blood: returns to the heart is distributed to systemic circuit

63. Pulmonary Vessels Pulmonary arteries: carry deoxygenated blood Pulmonary veins: carry oxygenated blood

64. Pulmonary Arteries Pulmonary trunk: branches to left and right pulmonary arteries Pulmonary arteries: branch into pulmonary arterioles Pulmonary arterioles: branch into capillary networks that surround alveoli

65. Pulmonary Veins Capillary networks around alveoli: join to form venules Venules: join to form 4 pulmonary veins Pulmonary veins: empty into left atrium

66. Major Systemic Arteries

67. Arteries of the Chest and Upper Limbs

68. Systemic Arteries Blood moves from left ventricle: into ascending aorta Coronary arteries: branch from aortic sinus

69. The Aorta The ascending aorta: rises from the left ventricle curves to form aortic arch turns downward to become descending aorta Branches of the Aortic Arch deliver blood to head and neck: brachiocephalic trunk left common carotid artery left subclavian artery

70. The Brachiocephalic Trunk Branches to form: right subclavian artery right common carotid artery The Subclavian Arteries Branches within thoracic cavity: internal thoracic artery vertebral artery thyrocervical trunk

71. The Subclavian Arteries The Subclavian Arteries Branches within thoracic cavity: internal thoracic artery vertebral artery thyrocervical trunk Leaving the thoracic cavity: become axillary artery in arm and brachial artery distally- Divides at coronoid fossa of humerus: into radial artery and ulnar artery

72. Arteries of the Neck and Head

73. The Common Carotid Arteries Carry blood to head and neck Each common carotid divides into: external carotid artery-Supplies structures of: Neck, lower jaw, face internal carotid artery-Enters skull and divides into: opthalmic artery, anterior cerebral artery, middle cerebral artery

74. Arteries of the Brain

75. The Vertebral Arteries Also supply brain with blood supply Left and right vertebral arteries: arise from subclavian arteries enter cranium through foramen magnum fuse to form basilar artery

76. Arteries of the Trunk

77. Arteries of the Trunk

78. 4 Visceral Branches Supply organs of the chest: bronchial arteries pericardial arteries esophogeal arteries mediastinal arteries

79. The Abdominal Aorta Divides at terminal segment of the aorta into: left common iliac artery right common iliac artery

80. Branches of the Abdominal Aorta Unpaired branches: major branches to visceral organs Paired branches: to body wall kidneys urinary bladder structures outside abdominopelvic cavity

81. Arteries of the Abdominopelvic Organs

82. 3 Unpaired Branches of the Abdominal Aorta Celiac trunk, divides into: left gastric artery splenic artery common hepatic artery Superior mesenteric artery Left mesenteric artery

83. 5 Paired Branches of the Abdominal Aorta Inferior phrenic arteries Suprarenal arteries Renal arteries Gonadal arteries Lumbar arteries

84. The Abdominal Aorta Divides to form: right and left common iliac arteries � Divide to form: internal iliac artery, external iliac artery middle sacral artery-

85. Arteries of the Lower Limbs

86. Major Systemic Veins

87. Complementary Arteries and Veins Run side by side Branching patterns of peripheral veins are more variable

88. Differences in Artery and Vein Distribution In neck and limbs: 1 set of arteries (deep) 2 sets of veins (1 deep, 1 superficial) Venous system controls body temperature

89. Veins of the Head, Neck, and Brain

90. The Superior Vena Cava (SVC) Receives blood from: head neck chest shoulders upper limbs

91. Veins of the Neck Temporal and maxillary veins: drain to external jugular vein Facial vein: drains to internal jugular vein

92. Veins of the Abdomen and Chest

93. Deep Veins of the Forearm Deep palmar veins drain into: radial and ulnar veins which fuse above elbow to form brachial vein Veins of the Upper Arm Cephalic vein joins axillary vein: to form subclavian vein

94. The Subclavian Vein Merges with external and internal jugular veins: to form brachiocephalic vein which enters thoracic cavity

95. Veins of the Thoracic Cavity Brachiocephalic vein receives blood from: vertebral vein internal thoracic vein Merge to form the superior vena cava (SVC)

96. Tributaries of the Superior Vena Cava

97. Tributaries of the Inferior Vena Cava

98. Veins of the Lower Limbs

99. The Femoral Vein Before entering abdominal wall, receives blood from: great saphenous vein deep femoral vein femoral circumflex vein Inside the pelvic cavity: becomes the external iliac vein The Right and Left Common Iliac Veins Merge to form the inferior vena cava

100. Veins of the Abdomen

101. The Hepatic Portal System

102. The Hepatic Portal System Connects 2 capillary beds Delivers nutrient-laden blood: from capillaries of digestive organs to liver sinusoids for processing

103. 5 Tributaries of the Hepatic Portal Vein Inferior mesenteric vein: drains part of large intestine Splenic vein: drains spleen, part of stomach, and pancreas Superior mesenteric vein: drains part of stomach, small intestine, and part of large intestine Left and right gastric veins: drains part of stomach Cystic vein: drains gallbladder

104. Blood Processed in Liver After processing in liver sinusoids, blood collects in hepatic veins and empties into inferior vena cava

105. Fetal Circulation Embryonic lungs and digestive tract nonfunctional Respiratory functions and nutrition provided by placenta

106. Placental Blood Supply

107. The Neonatal Heart

108. 2 Fetal Pulmonary Circulation Bypasses Foramen ovale: interatrial opening covered by valve-like flap directs blood from right to left atrium Ductus arteriosus: short vessel connects pulmonary and aortic trunks

109. Cardiovascular Changes at Birth Pulmonary vessels expand Reduced resistance allows blood flow Rising O2 causes ductus arteriosus constriction Rising left atrium pressure closes foramen ovale

110. Congenital Cardiovascular Problems

111. Aging and the Cardiovascular System Cardiovascular capabilities decline with age Age-related changes occur in: blood heart blood vessels

112. 3 Age-Related Changes in Blood Decreased hematocrit Blood clots (thrombus) Blood-pooling in legs due to venous valve deterioration

113. 5 Age-Related Changes in the Heart Reduced maximum cardiac output Changes in nodal and conducting cells Reduced elasticity of fibrous skeleton Progressive atherosclerosis Replacement of damaged cardiac muscle cells by scar tissue

114. 3 Age-Related Changes in Blood Vessels Arteries become less elastic: pressure change can cause aneurysm Calcium deposits on vessel walls: can cause stroke or infarction Thrombi can form: at atherosclerotic plaques

115. Integration with Other Systems

116. Clinical Patterns There are many categories of cardiovascular disorders Disorders may: affect all cells and systems be structural or functional result from disease or trauma

117. SUMMARY (1) 3 types of blood vessels: arteries veins Capillaries Structure of vessel walls Differences between arteries and veins Atherosclerosis, arteriosclerosis, and plaques Structures of: elastic arteries muscular arteries arterioles

118. SUMMARY (2) Structures of capillary walls: continuous Fenestrated Structures of capillary beds: precapillary sphincters vasomotion arteriovenous anastomoses Functions of the venous system and valves Distribution of blood and venous reserves

119. SUMMARY (3) Circulatory pressures: blood pressure capillary hydrostatic pressure venous pressure Resistance in blood vessels: viscosity turbulence Vasoconstriction The respiratory pump Capillary pressure and capillary exchange: osmotic pressure net filtration pressure

120. SUMMARY (4) Physiological controls of cardiovascular system: Autoregulation, neural controls hormonal controls Cardiovascular responses to exercise and blood loss Special circulation to brain, heart, and lungs Distribution of arteries in pulmonary and systemic circuits Distribution of veins in pulmonary and systemic circuits Fetal circulation and changes at birth Effects of aging on the cardiovascular system