(courtesy of Patricia Lee)Fig. 42-10: The Structure of Blood VesselsArtery VeinSEM100 mEndotheliumArterySmoothmuscleConnectivetissueCapillaryBasal laminaEndotheliumSmoothmuscleConnectivetissueValveVeinArterioleVenuleRed blood cellCapillary15 mLMDirection of blood flowin vein (toward heart)Valve (open)Skeletal muscleValve (closed)Fig. 42-14: Blood Flow in VeinsFig. 42-11:Relationshipof blood flow,velocity, cross-sectional area,& pressure.5,0004,0003,0002,0001,000005040302010120801006040200Area (cm2)Velocity(cm/sec)Pressure(mm Hg)AortaArteriesArteriolesCapillariesVenulesVeinsVenae cavaeDiastolicpressureSystolicpressureFig. 42-16: Fluid Exchange between Capillaries and Interstitial FluidBody tissueCapillaryINTERSTITIAL FLUIDNet fluidmovement outDirection ofblood flowNet fluidmovement inBlood pressureInward flowOutward flowOsmotic pressureArterial end of capillary Venous endPressureAt the arterial endof a capillary, bloodpressure is greaterthan osmoticpressure, and fluidflows out of thecapillary into theinterstitial fluid.At the venule endof a capillary, bloodpressure is lessthan osmoticpressure, and fluidflows from theinterstitial fluid intothe capillary.Fig. 42-15:Blood Flow inCapillary BedsPrecapillary sphinctersThoroughfarechannelArterioleCapillariesVenule(a) Sphincters relaxed(b) Sphincters contractedArteriole VenuleFig. 42-17: The Composition of Mammalian BloodPlasma 55%Constituent Major functionsWaterSolvent forcarrying othersubstancesIons (blood electrolytes)Osmotic balance,pH buffering, andregulation ofmembranepermeabilitySodiumPotassiumCalciumMagnesiumChlorideBicarbonateOsmotic balancepH bufferingClottingDefensePlasma proteinsAlbuminFibrinogenImmunoglobulins(antibodies)Substances transported by bloodNutrients (such as glucose, fatty acids, vitamins)Waste products of metabolismRespiratory gases (O2 and CO2)HormonesSeparatedbloodelementsCellular elements 45%Cell type FunctionsNumberper L (mm3) of bloodErythrocytes(red blood cells)5–6 millionTransport oxygenand help transportcarbon dioxideLeukocytes(white blood cells)5,000–10,000Defense andimmunityBasophilNeutrophilEosinophilLymphocyteMonocytePlatelets Blood clotting250,000–400,000Fig. 42-18: Blood ClottingCollagen fibersPlateletplugPlatelet releases chemicalsthat make nearby platelets stickyClotting factors from:PlateletsDamaged cellsPlasma (factors include calcium, vitamin K)Prothrombin ThrombinFibrinogen Fibrin5mFibrin clotRed blood cell1) Endothelium ofvesselis damaged,exposing connectivetissue;platelets adhere.2) Platelets form a plug.3) Seal is reinforced by a clotof fibrin. The clot results froma cascade
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