Cardio System II: Vasculature and PressureBlood Vessels: The Vascular SystemLayers of Blood VesselsDifferences Between Blood Vessel TypesSlide 5Arteries, ComparedSlide 7Capillaries and Capillary BedsCapillariesContinuous CapillariesPowerPoint PresentationFenestrated CapillariesSlide 13Sinusoidal CapillariesSlide 15Capillary BedsSlide 17Slide 18Venules and VeinsVeinsMost of the Blood is in Veins and VenulesVascular AnastomosesSlide 23PulsePhysiology of Circulation: Definition of TermsLocal Blood PressuresComparison of Blood PressuresFactors Aiding Venous ReturnMeasuring Arterial Blood PressureSlide 30Variations in Blood PressureSlide 32Cardio System II: Vasculature and Pressure Blood Vessel Anatomy•Arteries and arterioles•Capillaries (3 types)•Veins and venulesPulse and Pressure PointsBlood Pressure•Factors Regulating Blood PressureFigure 19.2Large veins(capacitancevessels)LargelymphaticvesselsArteriovenousanastomosisLymphaticcapillaryPostcapillaryvenuleSinusoidMetarterioleTerminal arterioleArterioles(resistance vessels)Muscular arteries(distributingvessels)Elastic arteries(conductingvessels)Small veins(capacitancevessels)LymphnodeCapillaries(exchange vessels)Precapillary sphincterThoroughfarechannelLymphaticsystemVenous systemArterial systemHeartBlood Vessels: The Vascular SystemLayers of Blood VesselsFigure 19.1bTunica media(smooth muscle under control of symp. n.s. andelastic fibers)Tunica externa(fibrous connective: collagen fibers)LumenArteryLumenVeinInternal elastic laminaExternal elastic laminaValve(b)Endothelial cellsBasement membraneCapillarynetworkCapillaryTunica intima• Endothelium• Subendothelial layerDifferences Between Blood Vessel TypesWalls of arteries are the thickest, while lumen is smaller in diameterWalls of veins are thinner, while lumens of veins are larger Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissueCardio System II: Vasculature and Pressure Blood Vessel Anatomy•Arteries and arterioles•Capillaries (3 types)•Veins and venulesPulse and Pressure PointsBlood Pressure•Factors Regulating Blood PressureTable 19.1 (1 of 2)Elastic ArteriesLarge thick-walled arteries with elastin in all three tunicsAorta and its major branchesLarge lumen offers low-resistance Act as pressure reservoirs—expand and recoil as blood is ejected from the heartMuscular ArteriesDistal to elastic arteries; deliver blood to body organsHave thick tunica media with more smooth muscleActive in vasoconstrictionArteriolesSmallest arteriesLead to capillary bedsControl flow into capillary beds via vasodilation and vasoconstrictionArteries, ComparedCardio System II: Vasculature and Pressure Blood Vessel Anatomy•Arteries and arterioles•Capillaries (3 types)•Veins and venulesPulse and Pressure PointsBlood Pressure•Factors Regulating Blood PressureLarge veins(capacitancevessels)LargelymphaticvesselsArteriovenousanastomosisLymphaticcapillaryPostcapillaryvenuleSinusoidMetarterioleTerminal arterioleArterioles(resistance vessels)Muscular arteries(distributingvessels)Elastic arteries(conductingvessels)Small veins(capacitancevessels)LymphnodeCapillaries(exchange vessels)Precapillary sphincterThoroughfarechannelLymphaticsystemVenous systemArterial systemHeartCapillaries and Capillary BedsFigure 19.2CapillariesFound in all tissues except for cartilage, epithelia, cornea and lens of eyeThree structural types1. Continuous capillaries2. Fenestrated capillaries3. Sinusoidal capillaries (sinusoids)Continuous CapillariesAbundant in the skin and muscles•Tight junctions connect endothelial cells •Intercellular clefts allow the passage of fluids and small solutesContinuous capillaries of the brain•Tight junctions are complete, forming the blood-brain barrierFigure 19.3aRed bloodcell in lumenIntercellularcleftEndothelialcellEndothelialnucleusTight junctionPinocytoticvesiclesPericyteBasementmembrane(a) Continuous capillary. Least permeable, and most common (e.g., skin, muscle).Fenestrated CapillariesSome endothelial cells contain pores (fenestrations)More permeable than continuous capillariesFunction in absorption or filtrate formation (small intestines, endocrine glands, and kidneys)Figure 19.3bRed bloodcell in lumenIntercellularcleftFenestrations(pores)EndothelialcellEndothelialnucleusBasement membraneTight junctionPinocytoticvesicles(b) Fenestrated capillary. Large fenestrations (pores) increase permeability. Occurs in special locations (e.g., kidney, small intestine).Sinusoidal CapillariesFewer tight junctions, larger intercellular clefts, large lumensUsually fenestratedAllow large molecules and blood cells to pass between the blood and surrounding tissuesFound in the liver, bone marrow, spleenFigure 19.3cNucleus ofendothelialcell Red bloodcell in lumenEndothelialcellTight junctionIncompletebasementmembraneLargeintercellularcleft(c) Sinusoidal capillary. Most permeable. Occurs in special locations (e.g., liver, bone marrow, spleen).Capillary BedsInterwoven networks of capillaries form the microcirculation between arterioles and venulesConsist of two types of vessels1. Vascular shunt (metarteriole—thoroughfare channel):oDirectly connects the terminal arteriole and a postcapillary venule2. True capillarieso10 to 100 exchange vessels per capillary bedoBranch off the metarteriole or terminal arterioleFigure 19.4(a) Sphincters open—blood flows through true capillaries.PrecapillarysphinctersMetarterioleVascular shuntTerminal arteriole Postcapillary venuleThoroughfare channelTrue capillariesPostcapillary venuleTerminal arteriole(b) Sphincters closed—blood flows through metarteriole thoroughfare channel and bypasses true capillaries.Blood Flow Through Capillary BedsHigh O2, low pH, nutrients, low CO2, cold external temperatures, fight or flight conditionsLow O2, high CO2, high pH, low nutrients, hot external temperatures, relaxationCardio System II: Vasculature and Pressure Blood Vessel Anatomy•Arteries and arterioles•Capillaries (3 types)•Veins and venulesPulse and Pressure PointsBlood Pressure•Factors Regulating Blood PressureTable 19.1 (2 of 2)VenulesFormed when capillary beds uniteVery porous; allow fluids and WBCs into tissuesPostcapillary venules consist of endothelium and a few pericytesLarger venules have one or two layers of smooth muscle cellsVeinsFormed when venules convergeHave
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