Chapter 21



Chapter 21 Blood Vessels and CirculationAn Introduction to Blood Vessels and CirculationLearning Outcomes21-1Distinguish among the types of blood vessels based on their structure and function, and describe how and where fluid and dissolved materials enter and leave the cardiovascular system.21-2Explain the mechanisms that regulate blood flow through vessels, describe the factors that influence blood pressure, and discuss the mechanisms that regulate movement of fluids between capillaries and interstitial spaces.An Introduction to Blood Vessels and Circulation Learning Outcomes21-3Describe the control mechanisms that regulate blood flow and pressure in tissues, and explain how the activities of the cardiac, vasomotor, and respiratory centers are coordinated to control blood flow through the tissues.21-4Explain the cardiovascular system’s homeostatic response to exercise and hemorrhaging, and identify the principal blood vessels and functional characteristics of the special circulation to the brain, heart, and lungs.An Introduction to Blood Vessels and CirculationLearning Outcomes21-5 Describe the three general functional patterns seen in the pulmonary and systemic circuits of the cardiovascular system.21-6Identify the major arteries and veins of the pulmonary circuit.21-7Identify the major arteries and veins of the systemic circuit.An Introduction to Blood Vessels and CirculationLearning Outcomes21-8 Identify the differences between fetal and adult circulation patterns, and describe the changes in the patterns of blood flow that occur at birth.21-9Discuss the effects of aging on the cardiovascular system, and give examples of interactions between the cardiovascular system and other organ systems.An Introduction to Blood Vessels and CirculationBlood VesselsAre classified by size and histological organizationAre instrumental in overall cardiovascular regulation21-1 Classes of Blood VesselsArteriesCarry blood away from heartArteriolesAre smallest branches of arteriesCapillariesAre smallest blood vesselsLocation of exchange between blood and interstitial fluidVenulesCollect blood from capillariesVeinsReturn blood to heart21-1 Blood VesselsThe Largest Blood VesselsAttach to heartPulmonary trunkCarries blood from right ventricleTo pulmonary circulationAortaCarries blood from left ventricleTo systemic circulation21-1 Blood VesselsThe Smallest Blood VesselsCapillariesHave small diameter and thin walls Chemicals and gases diffuse across walls21-1 Blood VesselsThe Structure of Vessel WallsWalls have three layers Tunica intima Tunica media Tunica externa21-1 Blood VesselsThe Tunica Intima (Inner Layer)Includes:The endothelial liningConnective tissue layerInternal elastic membraneIn arteries, is a layer of elastic fibers in outer margin of tunica intima 21-1 Blood VesselsThe Tunica Media (Middle Layer)Contains concentric sheets of smooth muscle in loose connective tissueBinds to inner and outer layersExternal elastic membrane of the tunica mediaSeparates tunica media from tunica externa21-1 Blood VesselsThe Tunica Externa (Outer Layer)Anchors vessel to adjacent tissues in arteriesContains collagen fibersElastic fibersIn veinsContains elastic fibersSmooth muscle cellsVasa vasorum (“vessels of vessels”)Small arteries and veinsIn walls of large arteries and veinsSupply cells of tunica media and tunica externa21-1 Blood VesselsDifferences between Arteries and VeinsArteries and veins run side by sideArteries have thicker walls and higher blood pressureCollapsed artery has small, round lumen (internal space)Vein has a large, flat lumenVein lining contracts, artery lining does notArtery lining folds Arteries more elastic Veins have valves21-1 Structure and Function of ArteriesArteriesElasticity allows arteries to absorb pressure waves that come with each heartbeatContractility Arteries change diameterControlled by sympathetic division of ANSVasoconstriction The contraction of arterial smooth muscle by the ANSVasodilation The relaxation of arterial smooth muscleEnlarging the lumen21-1 Structure and Function of ArteriesVasoconstriction and VasodilationAffect:Afterload on heartPeripheral blood pressureCapillary blood flow21-1 Structure and Function of ArteriesArteriesFrom heart to capillaries, arteries changeFrom elastic arteries To muscular arteries To arterioles21-1 Structure and Function of ArteriesElastic Arteries Also called conducting arteriesLarge vessels (e.g., pulmonary trunk and aorta) Tunica media has many elastic fibers and few muscle cellsElasticity evens out pulse force 21-1 Structure and Function of ArteriesMuscular Arteries Also called distribution arteriesAre medium sized (most arteries)Tunica media has many muscle cells21-1 Structure and Function of ArteriesArterioles Are smallHave little or no tunica externaHave thin or incomplete tunica media 21-1 Structure and Function of ArteriesArtery Diameter Small muscular arteries and arteriolesChange with sympathetic or endocrine stimulationConstricted arteries oppose blood flowResistance (R)Resistance vessels – arterioles21-1 Structure and Function of ArteriesAneurysmA bulge in an arterial wall Is caused by weak spot in elastic fibersPressure may rupture vessel21-1 Structure and Function of CapillariesCapillariesAre smallest vessels with thin wallsMicroscopic capillary networks permeate all active tissuesCapillary functionLocation of all exchange functions of cardiovascular systemMaterials diffuse between blood and interstitial fluid21-1 Structure and Function of CapillariesCapillary StructureEndothelial tube, inside thin basement membraneNo tunica mediaNo tunica externaDiameter is similar to red blood cell21-1 Structure and Function of CapillariesContinuous CapillariesHave complete endothelial liningAre found in all tissues except epithelia and cartilageFunctions of continuous capillariesPermit diffusion of water, small solutes, and lipid-soluble materialsBlock blood cells and plasma proteins21-1 Structure and Function of CapillariesSpecialized Continuous Capillaries Are in CNS and thymusHave very restricted permeabilityFor example, the blood–brain barrier21-1 Structure and Function of CapillariesFenestrated CapillariesHave pores in endothelial liningPermit rapid exchange of water and larger solutes between plasma and interstitial fluidAre found in:Choroid plexusEndocrine organsKidneysIntestinal tract21-1 Structure and Function of CapillariesSinusoids (Sinusoidal Capillaries)Have gaps between adjacent endothelial cellsLiverSpleenBone marrowEndocrine organsPermit free exchangeOf water and large plasma proteinsBetween blood and interstitial fluidPhagocytic cells monitor blood at sinusoids21-1 Structure and Function of CapillariesCapillary Beds (Capillary Plexus)Connect one arteriole and one venule Precapillary sphincter Guards entrance to each capillary Opens and closes, causing capillary blood to flow in pulses21-1 Structure and Function of CapillariesThoroughfare Channels Direct capillary connections between arterioles and venules Controlled by smooth muscle segments (metarterioles)21-1 Structure and Function of CapillariesCollaterals Multiple arteries that contribute to one capillary bed Allow circulation if one artery is blockedArterial anastomosisFusion of two collateral arteriesArteriovenous anastomoses Direct connections between arterioles and venulesBypass the capillary bed21-1 Structure and Function of CapillariesAngiogenesisFormation of new blood vesselsVascular endothelial growth factor (VEGF)Occurs in the embryo as tissues and organs developOccurs in response to factors released by cells that are hypoxic, or oxygen-starvedMost important in cardiac muscle, where it takes place in response to a chronically constricted or occluded vessel21-1 Structure and Function of CapillariesVasomotion Contraction and relaxation cycle of capillary sphincters Causes blood flow in capillary beds to constantly change routes21-1 Structure and Function of VeinsVeinsCollect blood from capillaries in tissues and organsReturn blood to heartAre larger in diameter than arteriesHave thinner walls than arteriesHave lower blood pressure21-1 Structure and Function of VeinsVenules Very small veinsCollect blood from capillariesMedium-Sized VeinsThin tunica media and few smooth muscle cellsTunica externa with longitudinal bundles of elastic fibers21-1 Structure and Function of VeinsLarge VeinsHave all three tunica layersThick tunica externaThin tunica media Venous ValvesFolds of tunica intima Prevent blood from flowing backwardCompression pushes blood toward heart21-1 Blood VesselsThe Distribution of BloodHeart, arteries, and capillaries30–35 percent of blood volumeVenous system60–65 percent 1/3 of venous blood is in the large venous networks of the liver, bone marrow, and skin21-1 Blood VesselsCapacitance of a Blood VesselThe ability to stretchRelationship between blood volume and blood pressureVeins (capacitance vessels) stretch more than arteries21-1 Blood VesselsVenous Response to Blood LossVasomotor center stimulates sympathetic nervesSystemic veins constrict (venoconstriction) Veins in liver, skin, and lungs redistribute venous reserve21-2 Pressure and ResistanceTotal Capillary Blood FlowEquals cardiac outputIs determined by:Pressure (P) and resistance (R) in the cardiovascular system21-2 Pressure and ResistancePressure (P)The heart generates P to overcome resistance Absolute pressure is less important than pressure gradientThe Pressure Gradient (?P)Circulatory pressureThe difference between:Pressure at the heartAnd pressure at peripheral capillary beds21-2 Pressure and ResistanceFlow (F) Is proportional to the pressure difference (?P) Divided by R21-2 Pressure and ResistanceMeasuring PressureBlood pressure (BP)Arterial pressure (mm Hg) Capillary hydrostatic pressure (CHP)Pressure within the capillary bedsVenous pressurePressure in the venous system21-2 Pressure and ResistanceCirculatory Pressure?P across the systemic circuit (about 100 mm Hg)Circulatory pressure must overcome total peripheral resistance R of entire cardiovascular system21-2 Pressure and ResistanceTotal Peripheral ResistanceVascular resistanceBlood viscosityTurbulence21-2 Pressure and ResistanceVascular ResistanceDue to friction between blood and vessel wallsDepends on vessel length and vessel diameterAdult vessel length is constantVessel diameter varies by vasodilation and vasoconstrictionR increases exponentially as vessel diameter decreases21-2 Pressure and ResistanceViscosity R caused by molecules and suspended materials in a liquidWhole blood viscosity is about four times that of water21-2 Pressure and ResistanceTurbulence Swirling action that disturbs smooth flow of liquidOccurs in heart chambers and great vesselsAtherosclerotic plaques cause abnormal turbulence21-2 Pressure and ResistanceAn Overview of Cardiovascular PressuresVessel diametersTotal cross-sectional areasPressuresVelocity of blood flow21-2 Pressure and ResistanceArterial Blood PressureSystolic pressurePeak arterial pressure during ventricular systoleDiastolic pressureMinimum arterial pressure during diastole21-2 Pressure and ResistanceArterial Blood PressurePulse pressure Difference between systolic pressure and diastolic pressure Mean arterial pressure (MAP)MAP = diastolic pressure + 1/3 pulse pressure21-2 Pressure and ResistanceAbnormal Blood PressureNormal = 120/80HypertensionAbnormally high blood pressureGreater than 140/90Hypotension Abnormally low blood pressure21-2 Pressure and ResistanceElastic ReboundArterial wallsStretch during systole Rebound (recoil to original shape) during diastole Keep blood moving during diastole21-2 Pressure and ResistancePressures in Small Arteries and ArteriolesPressure and distanceMAP and pulse pressure decrease with distance from heart Blood pressure decreases with frictionPulse pressure decreases due to elastic rebound21-2 Pressure and ResistanceVenous Pressure and Venous ReturnDetermines the amount of blood arriving at right atrium each minuteLow effective pressure in venous system21-2 Pressure and ResistanceVenous Pressure and Venous ReturnLow venous resistance is assisted by:Muscular compression of peripheral veinsCompression of skeletal muscles pushes blood toward heart (one-way valves) The respiratory pumpThoracic cavity action Inhaling decreases thoracic pressureExhaling raises thoracic pressure 21-2 Pressure and ResistanceCapillary Pressures and Capillary ExchangeVital to homeostasisMoves materials across capillary walls by:DiffusionFiltrationReabsorption21-2 Pressure and ResistanceDiffusionMovement of ions or moleculesFrom high concentrationTo lower concentrationAlong the concentration gradient21-2 Pressure and ResistanceDiffusion RoutesWater, ions, and small molecules such as glucoseDiffuse between adjacent endothelial cellsOr through fenestrated capillariesSome ions (Na+, K+, Ca2+, Cl?)Diffuse through channels in plasma membranes21-2 Pressure and ResistanceDiffusion RoutesLarge, water-soluble compoundsPass through fenestrated capillariesLipids and lipid-soluble materials such as O2 and CO2Diffuse through endothelial plasma membranesPlasma proteinsCross endothelial lining in sinusoids21-2 Pressure and ResistanceFiltration Driven by hydrostatic pressureWater and small solutes forced through capillary wallLeaves larger solutes in bloodstream21-2 Pressure and ResistanceReabsorption The result of osmotic pressure (OP)Blood colloid osmotic pressure (BCOP)Equals pressure required to prevent osmosisCaused by suspended blood proteins that are too large to cross capillary walls21-2 Pressure and ResistanceInterplay between Filtration and ReabsorptionEnsures that plasma and interstitial fluid are in constant communication and mutual exchangeAccelerates distribution of:Nutrients, hormones, and dissolved gases throughout tissues21-2 Pressure and ResistanceInterplay between Filtration and ReabsorptionAssists in the transport of:Insoluble lipids and tissue proteins that cannot enter bloodstream by crossing capillary wallsHas a flushing action that carries bacterial toxins and other chemical stimuli to:Lymphatic tissues and organs responsible for providing immunity to disease21-2 Pressure and ResistanceInterplay between Filtration and ReabsorptionNet hydrostatic pressureForces water out of solutionNet osmotic pressureForces water into solutionBoth control filtration and reabsorption through capillaries21-2 Pressure and ResistanceFactors that Contribute to Net Hydrostatic Pressure Capillary hydrostatic pressure (CHP) Interstitial fluid hydrostatic pressure (IHP) Net capillary hydrostatic pressure tends to push water and solutes:Out of capillariesInto interstitial fluid21-2 Pressure and ResistanceNet Capillary Colloid Osmotic Pressure Is the difference between: Blood colloid osmotic pressure (BCOP) and Interstitial fluid colloid osmotic pressure (ICOP) Pulls water and solutes:Into a capillaryFrom interstitial fluid21-2 Pressure and ResistanceNet Filtration Pressure (NFP)The difference between:Net hydrostatic pressureNet osmotic pressure NFP = (CHP – IHP) – (BCOP – ICOP)21-2 Pressure and ResistanceCapillary ExchangeAt arterial end of capillary:Fluid moves out of capillaryInto interstitial fluidAt venous end of capillary:Fluid moves into capillaryOut of interstitial fluid21-2 Pressure and ResistanceCapillary ExchangeTransition point between filtration and reabsorptionIs closer to venous end than arterial end Capillaries filter more than they reabsorbExcess fluid enters lymphatic vessels21-2 Pressure and ResistanceCapillary Dynamics HemorrhagingReduces CHP and NFPIncreases reabsorption of interstitial fluid (recall of fluids)DehydrationIncreases BCOPAccelerates reabsorptionIncrease in CHP or BCOP declinesFluid moves out of bloodBuilds up in peripheral tissues (edema)21-3 Cardiovascular RegulationTissue Perfusion Blood flow through the tissuesCarries O2 and nutrients to tissues and organsCarries CO2 and wastes awayIs affected by:Cardiac outputPeripheral resistanceBlood pressure21-3 Cardiovascular RegulationCardiovascular Regulation Changes Blood Flow to a Specific AreaAt an appropriate timeIn the right areaWithout changing blood pressure and blood flow to vital organs21-3 Cardiovascular RegulationControlling Cardiac Output and Blood PressureAutoregulationCauses immediate, localized homeostatic adjustmentsNeural mechanismsRespond quickly to changes at specific sitesEndocrine mechanismsDirect long-term changes21-3 Cardiovascular RegulationAutoregulation of Blood Flow within TissuesAdjusted by peripheral resistance while cardiac output stays the sameLocal vasodilators accelerate blood flow at tissue levelLow O2 or high CO2 levelsLow pH (acids)Nitric oxide (NO)High K+ or H+ concentrationsChemicals released by inflammation (histamine)Elevated local temperature21-3 Cardiovascular RegulationAutoregulation of Blood Flow within TissuesAdjusted by peripheral resistance while cardiac output stays the sameLocal vasoconstrictorsExamples: prostaglandins and thromboxanesReleased by damaged tissuesConstrict precapillary sphinctersAffect a single capillary bed21-3 Cardiovascular RegulationNeural MechanismsCardiovascular (CV) centers of the medulla oblongataCardiac centersCardioacceleratory center increases cardiac outputCardioinhibitory center reduces cardiac output21-3 Cardiovascular RegulationVasomotor CenterControl of vasoconstriction Controlled by adrenergic nerves (NE)Stimulates smooth muscle contraction in arteriole walls Control of vasodilationControlled by cholinergic nerves (NO)Relaxes smooth muscle Vasomotor ToneProduced by constant action of sympathetic vasoconstrictor nerves 21-3 Cardiovascular RegulationReflex Control of Cardiovascular FunctionCardiovascular centers monitor arterial bloodBaroreceptor reflexesRespond to changes in blood pressureChemoreceptor reflexesRespond to changes in chemical composition, particularly pH and dissolved gases21-3 Cardiovascular RegulationBaroreceptor ReflexesStretch receptors in walls of: Carotid sinuses (maintain blood flow to brain) Aortic sinuses (monitor start of systemic circuit) Right atrium (monitors end of systemic circuit)21-3 Cardiovascular RegulationBaroreceptor ReflexesWhen blood pressure rises, CV centers:Decrease cardiac outputCause peripheral vasodilationWhen blood pressure falls, CV centers:Increase cardiac outputCause peripheral vasoconstriction21-3 Cardiovascular RegulationChemoreceptor Reflexes Peripheral chemoreceptors in carotid bodies and aortic bodies monitor bloodCentral chemoreceptors below medulla oblongataMonitor cerebrospinal fluidControl respiratory functionControl blood flow to brain21-3 Cardiovascular RegulationChemoreceptor Reflexes Changes in pH, O2, and CO2 concentrations Produced by coordinating cardiovascular and respiratory activities 21-3 Cardiovascular RegulationCNS Activities and the Cardiovascular CentersThought processes and emotional states can elevate blood pressure by:Cardiac stimulation and vasoconstriction21-3 Cardiovascular RegulationHormones and Cardiovascular RegulationHormones have short-term and long-term effects on cardiovascular regulationFor example, E and NE from adrenal medullae stimulate cardiac output and peripheral vasoconstriction 21-3 Cardiovascular RegulationAntidiuretic Hormone (ADH)Released by neurohypophysis (posterior lobe of pituitary) Elevates blood pressureReduces water loss at kidneysADH responds to:Low blood volumeHigh plasma osmotic concentrationCirculating angiotensin II21-3 Cardiovascular RegulationAngiotensin II Responds to fall in renal blood pressureStimulates: Aldosterone productionADH productionThirstCardiac output and peripheral vasoconstriction21-3 Cardiovascular RegulationErythropoietin (EPO)Released at kidneys Responds to low blood pressure, low O2 content in bloodStimulates red blood cell production21-3 Cardiovascular RegulationNatriuretic PeptidesAtrial natriuretic peptide (ANP) Produced by cells in right atriumBrain natriuretic peptide (BNP) Produced by ventricular muscle cellsRespond to excessive diastolic stretchingLower blood volume and blood pressureReduce stress on heart21-4 Cardiovascular AdaptationBlood, Heart, and Cardiovascular SystemWork together as unit Respond to physical and physiological changes (for example, exercise and blood loss) Maintain homeostasis21-4 Cardiovascular AdaptationThe Cardiovascular Response to ExerciseLight ExerciseExtensive vasodilation occurs, increasing circulationVenous return increases with muscle contractionsCardiac output rises Venous return (Frank–Starling principle) Atrial stretching21-4 Cardiovascular AdaptationThe Cardiovascular Response to ExerciseHeavy ExerciseActivates sympathetic nervous system Cardiac output increases to maximum About four times resting levelRestricts blood flow to “nonessential” organs (e.g., digestive system) Redirects blood flow to skeletal muscles, lungs, and heartBlood supply to brain is unaffected21-4 Cardiovascular AdaptationExercise, Cardiovascular Fitness, and HealthRegular moderate exerciseLowers total blood cholesterol levelsIntense exerciseCan cause severe physiological stress21-4 Cardiovascular AdaptationThe Cardiovascular Response to HemorrhagingEntire cardiovascular system adjusts to:Maintain blood pressure Restore blood volume21-4 Cardiovascular AdaptationShort-Term Elevation of Blood PressureCarotid and aortic reflexesIncrease cardiac output (increasing heart rate)Cause peripheral vasoconstrictionSympathetic nervous systemTriggers hypothalamusFurther constricts arteriolesVenoconstriction improves venous return21-4 Cardiovascular AdaptationShort-Term Elevation of Blood PressureHormonal effectsIncrease cardiac outputIncrease peripheral vasoconstriction (E, NE, ADH, angiotensin II)21-4 Cardiovascular AdaptationShockShort-term responses compensate after blood losses of up to 20 percent of total blood volumeFailure to restore blood pressure results in shock21-4 Cardiovascular AdaptationLong-Term Restoration of Blood VolumeRecall of fluids from interstitial spacesAldosterone and ADH promote fluid retention and reabsorptionThirst increasesErythropoietin stimulates red blood cell production21-4 Cardiovascular AdaptationVascular Supply to Special RegionsThrough organs with separate mechanisms to control blood flowThree important examplesBrainHeartLungs21-4 Cardiovascular AdaptationBlood Flow to the BrainIs top priorityBrain has high oxygen demandWhen peripheral vessels constrict, cerebral vessels dilate, normalizing blood flow21-4 Cardiovascular AdaptationStroke Also called cerebrovascular accident (CVA)Blockage or rupture in a cerebral artery Stops blood flow21-4 Cardiovascular AdaptationBlood Flow to the HeartThrough coronary arteries Oxygen demand increases with activityLactic acid and low O2 levelsDilate coronary vesselsIncrease coronary blood flow21-4 Cardiovascular AdaptationBlood Flow to the HeartEpinephrineDilates coronary vesselsIncreases heart rateStrengthens contractions21-4 Cardiovascular AdaptationHeart AttackA blockage of coronary blood flowCan cause:Angina (chest pain)Tissue damageHeart failureDeath21-4 Cardiovascular AdaptationBlood Flow to the Lungs Regulated by O2 levels in alveoliHigh O2 contentVessels dilateLow O2 contentVessels constrict21-5 Pulmonary and Systemic PatternsThree General Functional PatternsPeripheral artery and vein distribution is the same on right and left, except near the heartThe same vessel may have different names in different locationsTissues and organs usually have multiple arteries and veinsVessels may be interconnected with anastomoses21-6 The Pulmonary CircuitDeoxygenated Blood Arrives at Heart from Systemic CircuitPasses through right atrium and right ventricleEnters pulmonary trunk At the lungsCO2 is removedO2 is addedOxygenated bloodReturns to the heart Is distributed to systemic circuit21-6 The Pulmonary CircuitPulmonary VesselsPulmonary arteriesCarry deoxygenated bloodPulmonary trunkBranches to left and right pulmonary arteries Pulmonary arteries Branch into pulmonary arteriolesPulmonary arteriolesBranch into capillary networks that surround alveoli21-6 The Pulmonary CircuitPulmonary VesselsPulmonary veinsCarry oxygenated bloodCapillary networks around alveoliJoin to form venulesVenulesJoin to form four pulmonary veinsPulmonary veinsEmpty into left atrium 21-7 The Systemic CircuitThe Systemic CircuitContains 84 percent of blood volumeSupplies entire bodyExcept for pulmonary circuit21-7 The Systemic CircuitSystemic ArteriesBlood moves from left ventricleInto ascending aortaCoronary arteriesBranch from aortic sinus21-7 The Systemic CircuitThe AortaThe ascending aortaRises from the left ventricleCurves to form aortic archTurns downward to become descending aortaFigure 21-20 Arteries of the Chest and Upper Limb.21-7 The Systemic CircuitBranches of the Aortic ArchDeliver blood to head, neck, shoulders, and upper limbs Brachiocephalic trunk Left common carotid artery Left subclavian artery21-7 The Systemic CircuitThe Subclavian Arteries Leaving the thoracic cavity:Become axillary artery in armAnd brachial artery distally21-7 The Systemic CircuitThe Brachial ArteryDivides at coronoid fossa of humerusInto radial artery and ulnar arteryFuse at wrist to form:Superficial and deep palmar archesWhich supply digital arteries21-7 The Systemic CircuitThe Common Carotid Arteries Each common carotid divides into:External carotid artery – supplies blood to structures of the neck, lower jaw, and faceInternal carotid artery – enters skull and delivers blood to brainDivides into three branches Ophthalmic artery Anterior cerebral artery Middle cerebral artery21-7 The Systemic CircuitThe Vertebral Arteries Also supply brain with bloodLeft and right vertebral arteriesArise from subclavian arteriesEnter cranium through foramen magnumFuse to form basilar artery Branches to form posterior cerebral arteriesPosterior cerebral arteriesBecome posterior communicating arteries21-7 The Systemic CircuitAnastomoses The cerebral arterial circle (or circle of Willis) interconnects:The internal carotid arteries And the basilar artery21-7 The Systemic CircuitThe Descending Aorta Thoracic aorta Supplies organs of the chestBronchial arteriesPericardial arteriesEsophageal arteriesMediastinal arteriesSupplies chest wallIntercostal arteriesSuperior phrenic arteries21-7 The Systemic CircuitThe Descending AortaAbdominal Aorta Divides at terminal segment of the aorta into:Left common iliac arteryRight common iliac arteryUnpaired branchesMajor branches to visceral organsPaired branchesTo body wallKidneysUrinary bladderStructures outside abdominopelvic cavity21-7 The Systemic CircuitArteries of the Pelvis and Lower LimbsFemoral arteryDeep femoral artery Becomes popliteal arteryPosterior to kneeBranches to form:Posterior and anterior tibial arteriesPosterior gives rise to fibular artery21-7 The Systemic CircuitSystemic VeinsComplementary Arteries and VeinsRun side by sideBranching patterns of peripheral veins are more variable In neck and limbsOne set of arteries (deep)Two sets of veins (one deep, one superficial)Venous system controls body temperature21-7 The Systemic CircuitThe Superior Vena Cava (SVC) Receives blood from the tissues and organs of:HeadNeckChestShouldersUpper limbs21-7 The Systemic CircuitThe Dural SinusesSuperficial cerebral veins and small veins of the brain stemEmpty into network of dural sinusesSuperior and inferior sagittal sinusesPetrosal sinusesOccipital sinusLeft and right transverse sinusesStraight sinus21-7 The Systemic CircuitCerebral VeinsGreat cerebral veinDrains to straight sinusOther cerebral veinsDrain to cavernous sinusWhich drains to petrosal sinusVertebral Veins Empty into brachiocephalic veins of chest21-7 The Systemic CircuitSuperficial Veins of the Head and NeckConverge to form:Temporal, facial, and maxillary veins Temporal and maxillary veinsDrain to external jugular veinFacial veinDrains to internal jugular vein21-7 The Systemic CircuitVeins of the HandDigital veinsEmpty into superficial and deep palmar veinsWhich interconnect to form palmar venous arches 21-7 The Systemic CircuitVeins of the HandSuperficial arch empties into:Cephalic veinMedian antebrachial vein Basilic veinMedian cubital veinDeep palmar veins drain into:Radial and ulnar veinsWhich fuse above elbow to form brachial vein21-7 The Systemic CircuitThe Brachial Vein Merges with basilic vein To become axillary veinCephalic vein joins axillary veinTo form subclavian veinMerges with external and internal jugular veins To form brachiocephalic veinWhich enters thoracic cavity21-7 The Systemic CircuitVeins of the Thoracic CavityBrachiocephalic vein receives blood from:Vertebral vein Internal thoracic vein The Left and Right Brachiocephalic Veins Merge to form the superior vena cava (SVC)21-7 The Systemic CircuitTributaries of the Superior Vena CavaAzygos vein and hemiazygos vein, which receive blood from:Intercostal veinsEsophageal veinsVeins of other mediastinal structures21-7 The Systemic CircuitThe Inferior Vena Cava (IVC)Collects blood from organs inferior to the diaphragm21-7 The Systemic CircuitVeins of the FootCapillaries of the soleDrain into a network of plantar veins Which supply the plantar venous archDrain into deep veins of leg:Anterior tibial veinPosterior tibial veinFibular vein All three join to become popliteal vein21-7 The Systemic CircuitThe Dorsal Venous Arch Collects blood from:Superior surface of footDigital veinsDrains into two superficial veins Great saphenous vein (drains into femoral vein) Small saphenous vein (drains into popliteal vein)21-7 The Systemic CircuitThe Popliteal Vein Becomes the femoral veinBefore entering abdominal wall, receives blood from:Great saphenous veinDeep femoral veinFemoral circumflex veinInside the pelvic cavityBecomes the external iliac vein21-7 The Systemic CircuitThe External Iliac Veins Are joined by internal iliac veins To form right and left common iliac veinsThe right and left common iliac veins Merge to form the inferior vena cava21-7 The Systemic CircuitMajor Tributaries of the Abdominal Inferior Vena Cava Lumbar veins Gonadal veins Hepatic veins Renal veins Adrenal veins Phrenic veins21-7 The Systemic CircuitThe Hepatic Portal System Connects two capillary bedsDelivers nutrient-laden bloodFrom capillaries of digestive organsTo liver sinusoids for processing21-7 The Systemic CircuitTributaries 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 Drain part of stomach Cystic vein Drains gallbladder21-7 The Systemic CircuitBlood Processed in LiverAfter processing in liver sinusoids (exchange vessels):Blood collects in hepatic veins and empties into inferior vena cava21-8 Fetal and Maternal CirculationFetal and Maternal Cardiovascular Systems Promote the Exchange of MaterialsEmbryonic lungs and digestive tract nonfunctionalRespiratory functions and nutrition provided by placenta21-8 Fetal and Maternal CirculationPlacental Blood SupplyBlood flows to the placentaThrough a pair of umbilical arteries that arise from internal iliac arteries Enters umbilical cordBlood returns from placentaIn a single umbilical vein that drains into ductus venosusDuctus venosusEmpties into inferior vena cava21-8 Fetal and Maternal CirculationBefore BirthFetal lungs are collapsedO2 provided by placental circulation21-8 Fetal and Maternal CirculationFetal Pulmonary Circulation BypassesForamen ovale Interatrial opening Covered by valve-like flapDirects blood from right to left atriumDuctus arteriosus Short vessel Connects pulmonary and aortic trunks21-8 Fetal and Maternal CirculationCardiovascular Changes at BirthNewborn breathes air Lungs expandPulmonary vessels expandReduced resistance allows blood flowRising O2 causes ductus arteriosus constrictionRising left atrium pressure closes foramen ovalePulmonary circulation provides O221-8 Fetal and Maternal CirculationPatent Foramen Ovale and Patent Ductus ArteriosusIn patent (open) foramen ovale blood recirculates through pulmonary circuit instead of entering left ventricleThe movement, driven by relatively high systemic pressure, is a “left-to-right shunt” Arterial oxygen content is normal, but left ventricle must work much harder than usual to provide adequate blood flow through systemic circuit 21-8 Fetal and Maternal CirculationPatent Foramen Ovale and Patent Ductus ArteriosusPressures rise in the pulmonary circuitIf pulmonary pressures rise enough, they may force blood into systemic circuit through ductus arteriosus A patent ductus arteriosus creates a “right-to-left shunt” Because circulating blood is not adequately oxygenated, it develops deep red colorSkin develops blue tones typical of cyanosis and infant is known as a “blue baby”21-8 Fetal and Maternal CirculationTetralogy of FallotComplex group of heart and circulatory defects that affect 0.10 percent of newborn infantsPulmonary trunk is abnormally narrow (pulmonary stenosis)Interventricular septum is incompleteAorta originates where interventricular septum normally ends Right ventricle is enlarged and both ventricles thicken in response to increased workload21-8 Fetal and Maternal CirculationVentricular Septal DefectOpenings in interventricular septum that separate right and left ventriclesThe most common congenital heart problems, affecting 0.12 percent of newborns Opening between the two ventricles has an effect similar to a connection between the atriaWhen more powerful left ventricle beats, it ejects blood into right ventricle and pulmonary circuit21-8 Fetal and Maternal CirculationAtrioventricular Septal DefectBoth the atria and ventricles are incompletely separatedResults are quite variable, depending on extent of defect and effects on atrioventricular valves This type of defect most commonly affects infants with Down’s syndrome, a disorder caused by the presence of an extra copy of chromosome 2121-8 Fetal and Maternal CirculationTransposition of Great VesselsThe aorta is connected to right ventricle instead of to left ventricleThe pulmonary artery is connected to left ventricle instead of right ventricleThis malformation affects 0.05 percent of newborn infants21-9 Effects of Aging and the Cardiovascular SystemCardiovascular Capabilities Decline with AgeAge-related changes occur in:BloodHeart Blood vessels21-9 Effects of Aging and the Cardiovascular SystemThree Age-Related Changes in BloodDecreased hematocritPeripheral blockage by blood clot (thrombus)Pooling of blood in legsDue to venous valve deterioration 21-9 Effects of Aging and the Cardiovascular SystemFive Age-Related Changes in the HeartReduced maximum cardiac outputChanges in nodal and conducting cellsReduced elasticity of cardiac (fibrous) skeletonProgressive atherosclerosisReplacement of damaged cardiac muscle cells by scar tissue21-9 Effects of Aging and the Cardiovascular SystemThree Age-Related Changes in Blood VesselsArteries become less elasticPressure change can cause aneurysmCalcium deposits on vessel wallsCan cause stroke or infarctionThrombi can formAt atherosclerotic plaques21-9 Cardiovascular System IntegrationMany Categories of Cardiovascular DisordersDisorders may:Affect all cells and systemsBe structural or functionalResult from disease or trauma ................
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