Blood Vessels and Circulation

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crzhazen
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68659
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Blood Vessels and Circulation
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2011-03-01 10:34:50
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Blood Vessels Circulation
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Blood Vessels and Circulation
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  1. Arteries
    Away from heart
  2. Veins
    Toward the heart
  3. Capillaries
    Connect small arteries and small veins
  4. Vessel Wall: Tunica Interna
    • Inner lining of blood vessel
    • Layer of epithelial cells
  5. Tunica Interna Functions
    • Selective permeable barrier
    • Secretes chemicals that affect dilation/vasoconstriction of vessel
    • Repels platelets to avoid clot formation
    • When tissue around vessel is inflamed, it produces cell-adhesion molecules to recruit leukocytes
  6. Tunica Media
    • Middle layer
    • Made of smooth muscle, collagen, and elastic tissue
  7. Tunica Media Functions
    • Strengthens vessel to prevent rupture
    • Vasomotion: change in dilation of blood vessel
  8. Tunica Externa
    • Outermost layer
    • Loose connective tissue
  9. Tunica Externa Function
    Anchors vessel to something
  10. Conducting Arteries
    • Biggest arteries
    • Aorta, pulmonary trunk, common carotid, subclavian, common iliac
    • Elastic tissue between wall layers
    • Expand during (ventricular) systole recoil during diastole
    • Decreases fluctuations in blood pressure
  11. Distributing Arteries
    • Carry blood to specific organs
    • Brachial, femoral, renal, splenic
    • Smooth muscle makes up most of wall
  12. Arterioles
    • Smalled arteries
    • Control amount of blood to various organs
    • Metarterioles: link arterioles to capillaries
  13. Aneurysm
    • Thin-walled bulging sac in artery wall
    • Often in abdominal aorta, renal arteries, and arterial circle surrounding hypothalamus
    • Often results from hypertension and/or atherosclerosis
    • Sometimes pain
    • Possibility of hemorrhage
  14. Capillaries
    Site of gas, nutrient, hormone, waste transfer between blood and tissue
  15. Continuous Capillaries
    • Most common tissues
    • Endothelial cells have tight junctions, allow for passage of glucose, oxygen
  16. Fenestrated Capillaries
    • Kidneys, endocrine glands, small intestine
    • Endothelial cells have lots of holes to allow for rapid absorption/filtration
  17. Sinusoids
    • Liver, bone marrow, spleen
    • Blood-filled spaces with large fenestrations to allow proteins, clotting factots, new blood cells to enter circulation
  18. Capillary Beds
    Network of capillaries supplied by metarteriole
  19. Precapillary Sphincter
    Regulates whether bed is perfused with blood
  20. Sphincter Open
    Blood Flows Through
  21. Sphincter Closed
    Blood bypasses capillaries through thoroughfare channel
  22. Veins vs Arteries
    • Greater Capacity of blood
    • Thinner walls, less muscular, and elastic tissue
    • Collapse when empty, expand when blood arrives
    • Blood is under little pressure
  23. Venules
    • Smallest Veins
    • Porous, so exchange fluid with surrounding tissue
    • Site of most leukocyte emigration
  24. Medium Veins
    • Thin walls
    • Tunica interna forms venous valves
    • Examples: radial, ulnar, saphenous veins
  25. Venous Valves
    • Muscle contraction pushes blood through valves to help get it up to the heart
    • Failure of these valves to operate causes varicose veins (blood pools in lower legs)
    • Hemorrhoids are varicose veins of anal canal
  26. Large Veins
    • Some smooth muscle in all wall layers
    • Venae cavae, pulmonary veins, internal jugular veins, renal veins
  27. Simple Pathway
    1 Capillary Bed
  28. Portal System
    2 Capillary Beds
  29. Arteriovenous Anastomosis
    Shunt
  30. Anastomosis
    Many branches
  31. Blood Pressure
    • Force exerted against vessel wall
    • Measured at brachial artery with sphygmomanometer
  32. 2 Components of Blood Pressure
    Systolic and Diastolic pressure
  33. Systolic Pressure
    Peak bp taken during ventricular systole
  34. Diastolic Pressure
    Minimum bp taken during ventricular diastole
  35. Normal BP
    Around 120/75 mm Hg
  36. Pulse Pressure
    Difference between systolic and diastolic pressure
  37. Mean Arterial Pressure (MAP)
    • Mean blood pressure throughout cycle
    • Best predictor of edema, fainting, atherosclerosis, kidney failure, aneurysm
  38. Elasticity of Arteries
    • Ability of arteries to stretch and recoil prevents excessive bp
    • Lose elasticity with age, which increases bp
  39. What determines blood pressure?
    • Determined by cardiac output, total blood volume, peripheral resistance
    • Resistance determined by blood viscosity, vessel length, vessel radius
  40. Hypertension
    • High bp
    • Resting bp greater than 140/90
    • Can weaken small arteries and cause aneurysms
  41. Hypotension
    Caused by blood loss, dehydration, anemia
  42. Autoregulation
    Tissues can regulate vasodilation/vasoconstriction
  43. Vasoactive Chemicals
    Platelets, endothelial cells, perivascular tissue affect vasomotion
  44. Reactive Hyperemia
    If blood flow is impacted (blocked), flow increases to compensate
  45. Angiogenesis
    Growth of new blood vessels
  46. Neural Control of BP
    • Vasomotor center in medulla controls sympathetic regulation of blood vessels
    • Stimulates vessels to constrict EXCEPT those in skeletal and cardiac muscles
  47. Angiotensin II
    Vasoconstrictor hormone released by the kidneys
  48. Aldosterone and ADH
    Promotes water retention so increases blood volume and pressure
  49. Epinephrine and Norepinephrine
    • Vasoconstriction of most blood vessels
    • Vasodilation of skeletal and cardiac muscle vessels
  50. Diffusion
    • Chemicals pass passively between blood and tissues
    • Steroid hormones, O2, CO2, go through plasma membranes of epithelial cells
    • Glucose and electrolytes pass through pores between cells
  51. Transcytosis
    • Endothelial cells pick up chemicals in vesicles and dump them out on other side
    • Fatty acids, albumin, some non-steroid hormones
  52. Filtration and Reabsoption
    • Fluid filters out of the arterial end of capillary and reenters at venous end
    • Delivers materials to cell and picks up waste
  53. Mechanisms of Venous Return
    • Pressure gradient
    • Gravity drains blood from head and neck
    • Skeletal muscle pumps: contracting muscle squeezes blood out
    • Thoracic Pump: inhalation increases abdominal pressure to force blood up
    • Cardiac Suction
  54. Pulmonary Circulation
    • Pulmonary arteries branch and go to lobes of the lungs
    • 3 lobes/branches on right, 2 on left
  55. Pulmonary Capillaries
    • Capillary beds form around alveoli
    • Site of gas exchange with air and lungs
  56. Ascending Aorta
    Right and Left coronary arteries
  57. Aortic Arch
    • Brachiocephalic: right carotid (supplying right side of head) and right subclavian (supplying right shoulder and arm)
    • Left Common Carotid: left side of head
    • Left Subclavian: left shoulder and arm
  58. Descending Aorta
    • Thoracic Aorta: above diaphragm
    • Abdominal Aorta: below diaphragm
  59. Arteries of Head and Neck
    • Common carotid divides into internal and external
    • External carotid supplies most of external head (everything but brain)
  60. Arteries of the Brain
    • Vertebral arteries combine to form basilar artery
    • Basilar artery and internal carotid arteries form Circle of Willis
    • Anterior, middle posterior cerebral arteries
    • Superior, anterior, posterior cerebellar arteries
  61. Blood Flow to Brain
    • Needs about 700 ml/min
    • Seconds of deprivation cause loss of consciousness
    • 4-5 minutes of loss cause irreversible brain damage
  62. Transient Ischemia Attack (TIA)
    • Brief episode of cerebral ischemia
    • Dizziness, loss of vision, weakness, paralysis, headache, aphasia
  63. Cerebral Vascular Accident (stroke)
    • Ischemia that causes death of brain tissue
    • Caused by atherosclerosis, thrombosis, or ruptured aneurysm
    • Blindness, paralysis, loss of sensation, loss of speech, sometimes death
  64. Veins of the Brain
    • Blood from brain flows into dural sinuses
    • Sinuses connect to internal jugular vein
  65. Veins of Head and Neck
    • External jugular vein receives blood from external parts of head
    • Arm drained by subclavian vein
  66. Arteries in the thorax
    • Thoracic aorta supplies viscera and body wall
    • Esophagus, lungs, spinal cord, vertebrae, diaphragm, back muscles, intercostal muscles
  67. Right Subclavian
    • Overlaps with thoracic aorta
    • Diaphragm, breast, pericardium, ribs, intercostal muscles, shoulder and pectoral muscles, some arm muscles
  68. Thoracic Veins
    Superior vena cava receives blood from upper thorax, head, neck and arms
  69. Abdominal Aorta
    • Branches supply lower trunk, adrenal gland, intestine, gonads, abdominal wall, spinal cord, sacrum, coccyx
    • Celiac trunk: supplies stomach, liver, pancreas and spleen
    • Mesenteric Arteries: supplies intestines, pancreas, colon, rectum
    • Renal Arteries: kidneys
    • Iliac arteries: supply legs
  70. Arteries in the Arm
    Arise from subclavian artery
  71. Veins in the Arm
    • Merge with jugular veins to form superior vena cava
    • Superficial veins carry more blood and are often visible
  72. Arteries of the Legs
    • Arise from iliac arteries
    • External iliac becomes femoral artery
  73. Veins of the Legs
    Iliac veins drain blood from legs into inferior vena cava

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