Y khoa, y dược - Chapter 18: The cardiovascular system

CHAPTER 18 The Cardiovascular System: The Heart: Part AHEART ANATOMYApproximately the size of a fistLocationIn the mediastinum between second rib and fifth intercostal spaceOn the superior surface of diaphragmTwo-thirds to the left of the midsternal lineAnterior to the vertebral column, posterior to the sternumEnclosed in pericardium, a double-walled sacPLAYAnimation: Rotatable heartFigure 18.1aPoint ofmaximalintensity(PMI)Diaphragm(a)Sternum2nd ribMidsternal lineFigure 18.1c(c)Superiorvena cavaLeft lungAortaParietalpleura (cut)Pericardium(cut)PulmonarytrunkDiaphragmApex ofheartPERICARDIUMSuperficial fibrous pericardiumProtects, anchors, and prevents overfillingPERICARDIUMDeep two-layered serous pericardiumParietal layer lines the internal surface of the fibrous pericardiumVisceral layer (epicardium) on external surface of the heartSeparated by fluid-filled pericardial cavity (decreases friction)Figure 18.2Fibrous pericardiumParietal layer ofserous pericardiumPericardial cavityEpicardium(visceral layerof serouspericardium)MyocardiumEndocardiumPulmonarytrunkHeart chamberHeartwallPericardiumMyocardiumLAYERS OF THE HEART WALLEpicardium—visceral layer of the serous pericardiumLAYERS OF THE HEART WALLMyocardium Spiral bundles of cardiac muscle cells Fibrous skeleton of the heart: crisscrossing, interlacing layer of connective tissueAnchors cardiac muscle fibers Supports great vessels and valvesLimits spread of action potentials to specific pathsLAYERS OF THE HEART WALLEndocardium is continuous with endothelial lining of blood vesselsFigure 18.2Fibrous pericardiumParietal layer ofserous pericardiumPericardial cavityEpicardium(visceral layerof serouspericardium)MyocardiumEndocardiumPulmonarytrunkHeart chamberHeartwallPericardiumMyocardiumCHAMBERS Four chambersTwo atriaSeparated internally by the interatrial septumCoronary sulcus (atrioventricular groove) encircles the junction of the atria and ventriclesAuricles increase atrial volumeCHAMBERS Two ventriclesSeparated by the interventricular septumAnterior and posterior interventricular sulci mark the position of the septum externallyFigure 18.4b(b) Anterior viewBrachiocephalic trunk Superior vena cavaRight pulmonaryarteryAscending aortaPulmonary trunkRight pulmonaryveinsRight atriumRight coronary artery(in coronary sulcus)Anterior cardiac veinRight ventricleRight marginal arterySmall cardiac veinInferior vena cavaLeft common carotidarteryLeft subclavian arteryLigamentum arteriosumLeft pulmonary arteryLeft pulmonary veinsCircumflex arteryLeft coronary artery(in coronary sulcus)Left ventricleGreat cardiac veinAnterior interventricularartery (in anteriorinterventricular sulcus)ApexAortic archAuricle ofleft atriumATRIA: THE RECEIVING CHAMBERSWalls are ridged by pectinate musclesVessels entering right atriumSuperior vena cava Inferior vena cavaCoronary sinusVessels entering left atriumRight and left pulmonary veinsVENTRICLES: THE DISCHARGING CHAMBERSWalls are ridged by trabeculae carneaePapillary muscles project into the ventricular cavitiesVessel leaving the right ventriclePulmonary trunkVessel leaving the left ventricleAortaFigure 18.4eAortaLeft pulmonaryarteryLeft atriumLeft pulmonaryveinsMitral (bicuspid)valveAortic valvePulmonary valveLeft ventriclePapillary muscleInterventricularseptumEpicardiumMyocardiumEndocardium(e) Frontal sectionSuperior vena cavaRight pulmonaryarteryPulmonary trunkRight atriumRight pulmonaryveinsFossa ovalisPectinate musclesTricuspid valveRight ventricleChordae tendineaeTrabeculae carneaeInferior vena cavaPATHWAY OF BLOOD THROUGH THE HEART The heart is two side-by-side pumpsRight side is the pump for the pulmonary circuitVessels that carry blood to and from the lungsLeft side is the pump for the systemic circuitVessels that carry the blood to and from all body tissuesFigure 18.5Oxygen-rich,CO2-poor bloodOxygen-poor,CO2-rich bloodCapillary bedsof lungs wheregas exchangeoccursCapillary beds of allbody tissues wheregas exchange occursPulmonary veinsPulmonary arteriesPulmonaryCircuitSystemicCircuitAorta and branchesLeft atriumHeartLeft ventricleRight atriumRight ventricleVenae cavaePATHWAY OF BLOOD THROUGH THE HEARTRight atrium  tricuspid valve  right ventricleRight ventricle  pulmonary semilunar valve  pulmonary trunk  pulmonary arteries  lungs Lungs  pulmonary veins  left atriumLeft atrium  bicuspid valve  left ventricleLeft ventricle  aortic semilunar valve  aorta  systemic circulation Systemic circulation  vena cavae  Right atriumPATHWAY OF BLOOD THROUGH THE HEARTEqual volumes of blood are pumped to the pulmonary and systemic circuitsPulmonary circuit is a short, low-pressure circulationSystemic circuit blood encounters much resistance in the long pathwaysAnatomy of the ventricles reflects these differencesFigure 18.6RightventricleLeftventricleInterventricularseptumCORONARY CIRCULATIONThe functional blood supply to the heart muscle itselfArterial supply varies considerably and contains many anastomoses (junctions) among branchesCollateral routes provide additional routes for blood deliveryCORONARY CIRCULATIONArteries Right and left coronary (in atrioventricular groove), marginal, circumflex, and anterior interventricular arteriesVeins Small cardiac, anterior cardiac, and great cardiac veinsFigure 18.7aRightventricleRightcoronaryarteryRightatriumRightmarginalarteryPosteriorinterventriculararteryAnteriorinterventriculararteryCircumflexarteryLeftcoronaryarteryAortaAnastomosis(junction ofvessels)LeftventricleSuperiorvena cava(a) The major coronary arteriesLeft atriumPulmonarytrunkFigure 18.7bSuperiorvena cavaAnteriorcardiacveinsSmall cardiac veinMiddle cardiac veinGreatcardiacveinCoronarysinus(b) The major cardiac veinsFigure 18.4d(d) Posterior surface viewAortaLeft pulmonaryarteryLeft pulmonaryveinsAuricle of leftatriumLeft atriumGreat cardiacveinPosterior veinof left ventricleLeft ventricleApexSuperior vena cavaRight pulmonary arteryRight pulmonary veinsRight atriumInferior vena cavaRight coronary artery(in coronary sulcus)Coronary sinusPosteriorinterventricularartery (in posteriorinterventricular sulcus)Middle cardiac veinRight ventricleHOMEOSTATIC IMBALANCESAngina pectorisThoracic pain caused by a fleeting deficiency in blood delivery to the myocardiumCells are weakenedMyocardial infarction (heart attack)Prolonged coronary blockageAreas of cell death are repaired with noncontractile scar tissueHEART VALVESEnsure unidirectional blood flow through the heartAtrioventricular (AV) valvesPrevent backflow into the atria when ventricles contractTricuspid valve (right)Mitral valve (left)Chordae tendineae anchor AV valve cusps to papillary musclesHEART VALVESSemilunar (SL) valvesPrevent backflow into the ventricles when ventricles relaxAortic semilunar valvePulmonary semilunar valveFigure 18.8aPulmonary valveAortic valveArea of cutawayMitral valveTricuspid valveMyocardiumTricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalvePulmonaryvalve(b)Pulmonary valveAortic valveArea of cutawayMitral valveTricuspid valveMyocardiumTricuspid(right atrioventricular)valve(a)Mitral(left atrioventricular)valveAortic valvePulmonaryvalveFibrousskeletonAnteriorFigure 18.8bPulmonary valveAortic valveArea of cutawayMitral valveTricuspid valveMyocardiumTricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalvePulmonaryvalve(b)Figure 18.8cPulmonaryvalveAorticvalveArea ofcutawayMitralvalveTricuspidvalveChordae tendineaeattached to tricuspid valve flapPapillarymuscle(c)Figure 18.8dPulmonaryvalveAortic valveArea of cutawayMitral valveTricuspidvalveMitral valveChordaetendineaeInterventricularseptumMyocardiumof left ventricleOpening of inferiorvena cavaTricuspid valvePapillarymusclesMyocardiumof rightventricle(d)Figure 18.91 Blood returning to theheart fills atria, puttingpressure againstatrioventricular valves;atrioventricular valves areforced open.1 Ventricles contract, forcingblood against atrioventricularvalve cusps.2 As ventricles fill,atrioventricular valve flapshang limply into ventricles.2 Atrioventricular valvesclose.3 Atria contract, forcingadditional blood into ventricles.3 Papillary musclescontract and chordaetendineae tighten,preventing valve flapsfrom everting into atria.(a) AV valves open; atrial pressure greater than ventricular pressure(b) AV valves closed; atrial pressure less than ventricular pressureDirection ofblood flowAtriumVentricleCusp ofatrioventricularvalve (open)ChordaetendineaePapillarymuscleAtriumBlood inventricleCusps ofatrioventricularvalve (closed)Figure 18.10As ventriclescontract andintraventricularpressure rises,blood is pushed upagainst semilunarvalves, forcing themopen.As ventricles relaxand intraventricularpressure falls, bloodflows back fromarteries, filling thecusps of semilunarvalves and forcingthem to close.(a) Semilunar valves open(b) Semilunar valves closedAortaPulmonarytrunkMICROSCOPIC ANATOMY OF CARDIAC MUSCLECardiac muscle cells are striated, short, fat, branched, and interconnectedNumerous large mitochondria (25–35% of cell volume) Intercalated discs: junctions between cells anchor cardiac cells Heart muscle behaves as a functional syncytiumFigure 18.11aNucleusDesmosomesGap junctionsIntercalated discsCardiac muscle cell(a)