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Circulatory Systems

Circulatory Systems

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Circulatory Systems

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  1. Circulatory Systems Transport & Maintenance

  2. Circulatory Systems • transport to & from tissues • nutrients, O2; waste, CO2 • hormones • maintain electrolyte balance of intercellular fluid • transport to/from homeostatic organs • small intestine delivers nutrients • liver removes wastes, controls nutrients • kidney controls electrolytes, dumps wastes

  3. Circulatory Systems • some animals lack circulatory systems • aquatic environment fulfills same functions • some animals have open circulatory systems • the heart pumps interstitial fluid • vessels deliver interstitial fluid to tissues • interstitial fluids leave the vessels & bathe the cells of the tissues • interstitial fluids return to the heart • other animals have closed circulatory systems

  4. open circulatory systemsFigure 49.1

  5. closed circulatory system of earthwormFigure 49.2

  6. Closed Circulatory Systems • components of closed circulatory systems • heart(s) - pump • vessels - transport conduits • blood - • transport medium • distinct from interstitial fluid • advantages over open system • speed • control of blood flow • cellular elements of blood remain in vessels

  7. Circulatory Systems • hearts • vertebrates have chambered hearts • valves impose one-way flow • number of chambers varies with phylogeny • blood circulates through one or two circuits • H => G.E.M. => B • H => G.E.M. => H => B pulmonary systemic circuit circuit

  8. Closed Circulatory Systems • vessels • arteries • transport blood away from heart • veins • transport blood toward heart • arterioles/venules • small arteries/veins • capillaries • connect arterioles to venules

  9. Closed Circulatory Systems • systems with two-chambered hearts - fish • one circuit • atrium =>ventricle =>gills =>aorta =>body =>atrium • ventricular pressure is dissipated in gill capillaries

  10. fish circulation schematicp. 943

  11. Closed Circulatory Systems • systems with two-chambered hearts - lungfish • modified for breathing air or water • out-pocketing of gut acts as a lung • some gill arteries supply blood to lung • some gill arteries deliver blood to aorta • gills exchange gases with water • partially separated atrium • right side => oxygenated blood => body • left side => deoxygenated blood => gills/lungs

  12. lungfish circulation schematicp. 943 * one pair of gill arteries delivers blood to lung * two gill arches deliver blood directly to aorta * “gilled” gill arches exchange gases with blood

  13. Closed Circulatory Systems • systems with three-chambered hearts - amphibians • two atria • left atrium receives pulmonary blood • right atrium receives systemic blood • ventricle anatomy limits mixing • deoxygenated blood travels to lung • oxygenated blood travels to body

  14. amphibian circulation schematicp. 943

  15. Closed Circulatory Systems • reptilian hearts provide further control • two atria receive blood from pulmonary & systemic circuits • partially separated ventricle supplies three vessels • pulmonary artery & two aortas • when breathing, the right aorta carries deoxygenated blood to the pulmonary circuit • when not breathing, both aortas carry blood to the systemic circuit

  16. reptilian circulation schematicp. 944

  17. Closed Circulatory Systems • crocodilian hearts have four chambers • two atria, two ventricles, two aortas • two aortas are bridged near their origins • when breathing, the left ventricle (& aorta) pressure is higher • deoxygenated blood goes to lungs • when not breathing, right aorta pressure is higher • pulmonary circuit is bypassed

  18. crocodilian schematicp. 944

  19. Closed Circulatory Systems • endotherm hearts have four chambers and one aorta • systemic/pulmonary circuits are separated • tissues receive highest possible [O2] (P1) under high pressure • lungs receive lowest possible [O2] (P2) under lower pressure

  20. endotherm schematicp. 945

  21. human circulatory systemFigure 49.3

  22. Human Circulatory System • circulation • deoxygenated blood arrives at right atrium from inferior & superior vena cava • atrium pumps blood to right ventricle • ventricle pumps blood to pulmonary artery • backflow is prevented by atrioventricular valve • ventricle relaxes • backflow is prevented by pulmonary valve

  23. human heart anatomyFigure 49.3

  24. Human Circulatory System • circulation • oxygenated blood arrives at left atrium through pulmonary veins • atrium pumps blood into left ventricle • ventricle pumps blood to aorta • backflow is prevented by atrioventricular valve • ventricle relaxes • backflow is prevented by aortic valve

  25. human heart anatomyFigure 49.3

  26. Human Circulatory System • cardiac cycle • systole - contraction of ventricles • maximum pressure generated • major electrical event • diastole - relaxation of ventricles • minimum pressure • characteristic electrical signatures

  27. ventricular pressures & volumesFigure 49.4

  28. measuring blood pressureFigure 49.5

  29. Human Circulatory System • heartbeat is myogenic • pacemaker cells occur at sinoatrial node • resting membrane potential depolarizes • at threshold, voltage gated Ca2+ channels open • K+ channels open to repolarize cells • K+ channels close slowly, allow gradual depolarization • autonomic nervous system regulates the rate of depolarization

  30. autonomic control of heart rateFigure 49.6Figure 49.8Figure 44. 9 norepinephrine acetylcholine

  31. Human Circulatory System • contraction • the pacemaker action potential spreads across the atrial walls • atria contract • action potential is transmitted to ventricles through the atrioventricular node and the bundle of His • the action potential spreads to Purkinje fibers in ventricular muscle • ventricles contract

  32. origin and spread of cardiac contractionFigure 49.7

  33. Human Circulatory System • vascular system • arteries carry blood from heart • elastic tissues absorb pressure of heart contractions • smooth muscle allows control of blood flow by neural and hormonal signals

  34. artery structureFigure 49.10

  35. Human Circulatory System • vascular system • capillaries • fed by arterioles; drained by venules • exchange materials between blood & intercellular fluids • high total capacity; slow flow • thin walls

  36. capillary bedFigure 49.10

  37. Human Circulatory System • vascular system • capillaries • exchange materials by filtration, osmosis & diffusion • water & solutes move through capillary walls under pressure on the arteriole side • remaining solutes & diffusing CO2 produce a low osmotic potential • water returns to capillaries on the venule side

  38. water movement balanced between blood pressure & osmotic potentialFigure 49.12

  39. Human Circulatory System • [lymphatics • lymph vessels return excess tissue fluid to blood • lymphatic capillaries collect lymph • capillaries merge into larger vessels • vessels contain one-way valves • the major lymph vessel, the thoracic duct, empties into the superior vena cava • lymph nodes participate in lymphocyte production & phagocyte activity]

  40. vein structureFigure 49.10

  41. Human Circulatory System • veins • receive blood from capillaries under low pressure • contain one-way valves • blood is propelled by skeletal muscle contraction or gravity

  42. venous return by skeletal muscle contraction and one-way valves

  43. Human Circulatory System • blood - a fluid connective tissue • fluid matrix - plasma • dissolved gases, ions, proteins, nutrients, hormones, etc. • many components found in tissue fluid • cellular elements • red blood cells (erythrocytes) • white blood cells (leukocytes) • platelets

  44. blood componentsFigure 49.15

  45. human blood samplesbeforeand aftercentrifugation to separate red blood cells from serum

  46. Human Circulatory System • control & regulation of circulation • capillaries are subject to auto-regulation • pre-capillary sphincters and arterial smooth muscle are sensitive to • O2 & CO2 concentrations • accumulated waste materials

  47. local control of blood flowFigure 49.17

  48. Human Circulatory System • control & regulation of circulation • simultaneous auto-regulation of capillary beds produces systemic responses • changes in breathing, heart rate • changes in blood distribution • systemic control is neural or hormonal • sympathetic stimulation contracts most arteries; dilates skeletal muscle arteries • hormones constrict arteries in targeted tissues

  49. circulatory regulation at two levelsFigure 49.18

  50. Human Circulatory System • control & regulation of circulation • autonomic control of circulation originates in medulla of brain stem • inputs arrive from • stretch receptors • chemosensors • higher brain centers • responses may be • direct - artery relaxation or contraction • indirect - release of epinephrine