1. Copyright 2010, John Wiley & Sons, Inc. Chapter 15 The Cardiovascular System: The Heart

2. Copyright 2010, John Wiley & Sons, Inc. Location of the Heart Thoracic cavity between two lungs  ~2/3 to left of midline surrounded by pericardium: Fibrous pericardium -  Inelastic and anchors heart in place Inside is serous pericardium - double layer around heart  Parietal layer fused to fibrous pericardium  Inner visceral layer adheres tightly to heart  Filled with pericardial fluid - reduces friction during beat.

3. Copyright 2010, John Wiley & Sons, Inc. Position of the Heart

4. Copyright 2010, John Wiley & Sons, Inc. Position of the Heart

5. Copyright 2010, John Wiley & Sons, Inc. Heart Wall Epicardium - outer layer Myocardium - cardiac muscle  Two separate networks via gap junctions in intercalated discs - atrial & ventricular  Networks- contract as a unit Endocardium - Squamous epithelium  lines inside of myocardium

6. Copyright 2010, John Wiley & Sons, Inc. Pericardium

7. Copyright 2010, John Wiley & Sons, Inc. Cardiac Muscle Tissue

8. Copyright 2010, John Wiley & Sons, Inc. Chambers of the Heart 4 chambers 2 upper chambers = Atria  Between is interatrial septum 2 lower chambers = ventricles  Between is interventricular septum Wall thickness depends on work load  Atria thinnest  Right ventricle pumps to lungs & thinner than left

9. Copyright 2010, John Wiley & Sons, Inc. Structure of the Heart

10. Copyright 2010, John Wiley & Sons, Inc. Structure of the Heart

11. Copyright 2010, John Wiley & Sons, Inc. Great Vessels Of Heart-Right Superior & inferior Vena Cavae  Delivers deoxygenated blood to R. atrium from body  Coronary sinus drains heart muscle veins R. Atrium  R. Ventricle pumps through Pulmonary Trunk  R & L pulmonary arteries  lungs

12. Copyright 2010, John Wiley & Sons, Inc. Great Vessels Of Heart-Left Pulmonary Veins from lungs  oxygenated blood  L. atrium  Left ventricle  ascending aorta  body Between pulmonary trunk & aortic arch is ligamentum arteriosum fetal ductus arteriosum remnant

13. Copyright 2010, John Wiley & Sons, Inc. Anterior View of Frontal Section

14. Copyright 2010, John Wiley & Sons, Inc. Valves Designed to prevent back flow in response to pressure changes Atrioventricular (AV) valves  Between atria and ventricles Right = tricuspid valve (3 cusps) Left = bicuspid or mitral valve Semilunar valves near origin of aorta & pulmonary trunk Aortic & pulmonary valves respectively

15. Copyright 2010, John Wiley & Sons, Inc. Atrioventricular Valves: Bicuspid Valves

16. Copyright 2010, John Wiley & Sons, Inc. Atrioventricular Valves: Superior View

17. Copyright 2010, John Wiley & Sons, Inc. Blood Flow Through Heart

18. Copyright 2010, John Wiley & Sons, Inc. Blood Flow

19. Copyright 2010, John Wiley & Sons, Inc. Conduction System 1% of cardiac muscle generate action potentials= Pacemaker & Conduction system Normally begins at sinoatrial (SA) node  Atria & atria contract  AV node - slows  AV bundle (Bundle of His)  bundle branches  Purkinje fibers  apex and up- then ventricles contract

20. Copyright 2010, John Wiley & Sons, Inc. Pacemaker Depolarize spontaneously sinoatrial node ~100times /min also AV node ~40-60 times/min in ventricle ~20-35 /min Fastest one run runs the heart = pacemaker Normally the sinoatrial node

21. Copyright 2010, John Wiley & Sons, Inc. Frontal plane Right atrium Right ventricle Left atrium Left ventricle Anterior view of frontal section Frontal plane Left atrium Left ventricle Anterior view of frontal section SINOATRIAL (SA) NODE 1 Right atrium Right ventricle Frontal plane Left atrium Left ventricle Anterior view of frontal section SINOATRIAL (SA) NODE ATRIOVENTRICULAR (AV) NODE 1 2 Right atrium Right ventricle Frontal plane Left atrium Left ventricle Anterior view of frontal section SINOATRIAL (SA) NODE ATRIOVENTRICULAR (AV) NODE ATRIOVENTRICULAR (AV) BUNDLE (BUNDLE OF HIS) 1 2 3 Right atrium Right ventricle Frontal plane Left atrium Left ventricle Anterior view of frontal section SINOATRIAL (SA) NODE ATRIOVENTRICULAR (AV) NODE ATRIOVENTRICULAR (AV) BUNDLE (BUNDLE OF HIS) RIGHT AND LEFT BUNDLE BRANCHES 1 2 3 4 Right atrium Right ventricle Frontal plane SINOATRIAL (SA) NODE ATRIOVENTRICULAR (AV) NODE Left atrium Left ventricle Anterior view of frontal section ATRIOVENTRICULAR (AV) BUNDLE (BUNDLE OF HIS) RIGHT AND LEFT BUNDLE BRANCHES PURKINJE FIBERS 1 2 3 4 5 Right atrium Right ventricle

22. Copyright 2010, John Wiley & Sons, Inc. Electrocardiogram Recording of currents from cardiac conduction on skin = electrocardiogram (EKG or ECG) P wave = atrial depolarization  Contraction begins right after peak  Repolarization is masked in QRS QRS complex = Ventricular depolarization  Contraction of ventricle T-wave = ventricular repolarization  Just after ventricles relax

23. Copyright 2010, John Wiley & Sons, Inc. ECG

24. Copyright 2010, John Wiley & Sons, Inc. Cardiac Cycle after T-wave  ventricular diastole  Ventricular pressure drops below atrial & AV valves open  ventricular filling occurs After P-wave  atrial systole  Finishes filling ventricle (`25%) After QRS  ventricular systole  Pressure pushes AV valves closed  Pushes semilunar valves open and ejection occurs  Ejection until ventricle relaxes enough for arterial pressure to close semilunar valves

25. Copyright 2010, John Wiley & Sons, Inc. Cardiac Cycle

26. Copyright 2010, John Wiley & Sons, Inc. Flow Terms Cardiac Output (CO) = liters/min pumped Heart Rate (HR) = beats/minute (bpm) Stroke volume (SV) = volume/beat CO = HR x SV

27. Copyright 2010, John Wiley & Sons, Inc. Exercise and the Heart Aerobic exercise (longer than 20 min) strengthens cardiovascular system Well trained athlete  doubles maximum C.O. Resting C.O. about the same but resting H.R. decreased