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The Heart

The Heart. Function of the Heart. Pumping the red stuff Anatomy of the Heart Location – mediastinum, slightly to the left of center Size – about that of your fist Mass – 250 – 300 g. Organization of the Cardiovascular System. Location. Tissues of the Heart.

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The Heart

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  1. The Heart

  2. Function of the Heart • Pumping the red stuff Anatomy of the Heart • Location – mediastinum, slightly to the left of center • Size – about that of your fist • Mass – 250 – 300 g

  3. Organization of the Cardiovascular System

  4. Location

  5. Tissues of the Heart

  6. Coverings of the Heart: Anatomy • Pericardium – a double-walled sac around the heart composed of: • A superficial fibrous pericardium • A deep two-layer serous pericardium • The parietal layer lines the internal surface of the fibrous pericardium • The visceral layer or epicardium lines the surface of the heart • They are separated by the fluid-filled pericardial cavity

  7. Coverings of the Heart: Physiology • The pericardium: • Protects and anchors the heart • Prevents overfilling of the heart with blood • Allows for the heart to work in a relatively friction-free environment

  8. Serous pericardium

  9. General Anatomy

  10. Heart Wall • Epicardium – visceral layer of the serous pericardium • Myocardium – cardiac muscle layer forming the bulk of the heart • Fibrous skeleton of the heart – crisscrossing, interlacing layer of connective tissue • Endocardium – endothelial layer of the inner myocardial surface

  11. Heart Wall

  12. External Heart: Major Vessels of the Heart (Anterior View) • Vessels returning blood to the heart include: • Superior and inferior venae cavae • Right and left pulmonary veins • Vessels conveying blood away from the heart include: • Pulmonary trunk, which splits into right and left pulmonary arteries • Ascending aorta (three branches) – brachiocephalic, left common carotid, and subclavian arteries

  13. External Heart: Vessels that Supply/Drain the Heart (Anterior View) • Arteries – right and left coronary (in atrioventricular groove), marginal, circumflex, and anterior interventricular arteries • Veins – small cardiac, anterior cardiac, and great cardiac veins

  14. Surface features of the heart

  15. Cardiac Muscle Cells

  16. External Heart: Major Vessels of the Heart (Posterior View) • Vessels returning blood to the heart include: • Right and left pulmonary veins • Superior and inferior venae cavae • Vessels conveying blood away from the heart include: • Aorta • Right and left pulmonary arteries

  17. Posterior view

  18. Atria of the Heart • Atria are the receiving chambers of the heart • Each atrium has a protruding auricle • Pectinate muscles mark atrial walls • Blood enters right atria from superior and inferior venae cavae and coronary sinus • Blood enters left atria from pulmonary veins

  19. Ventricles of the Heart • Ventricles are the discharging chambers of the heart • Papillary muscles and trabeculae carneae muscles mark ventricular walls • Right ventricle pumps blood into the pulmonary trunk • Left ventricle pumps blood into the aorta

  20. Deep in your heart of hearts…

  21. Note the differences in wall thickness

  22. Heart Valves • Heart valves ensure unidirectional blood flow through the heart • Atrioventricular (AV) valves lie between the atria and the ventricles • AV valves prevent backflow into the atria when ventricles contract • Chordae tendineae anchor AV valves to papillary muscles • Aortic semilunar valve lies between the left ventricle and the aorta • Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk • Semilunar valves prevent backflow of blood into the ventricles

  23. The heart valves

  24. The heart valves

  25. Function of the bicuspid valve

  26. Valve functions

  27. Heart Sounds

  28. Where to go to listen to heart sounds

  29. Some heart valve disorders • Stenosis (narrowing) – the inability of a valve to open fully • Insufficiency (incompetence) – failure of the valve to prevent back flow or close properly • Mitral valve prolapse – one or both of the flaps blows back into the atrium during systole (contraction) of the ventricle allowing backflow into the atrium. • The aortic semilunar valves can also suffer from stenosis or insufficiency, allowing backflow into the ventricle.

  30. Pathway of Blood Through the Heart and Lungs • Right atrium  tricuspid valve  right ventricle • Right ventricle  pulmonary semilunar valve  pulmonary arteries  lungs • Lungs  pulmonary veins  left atrium • Left atrium  bicuspid valve  left ventricle • Left ventricle  aortic semilunar valve  aorta • Aorta  systemic circulation

  31. Systemic & pulmonary circuits

  32. Blood flow

  33. Coronary Circulation • Coronary circulation is the functional blood supply to the heart muscle itself • Collateral routes ensure blood delivery to heart even if major vessels are occluded

  34. Coronary Circulation(arterial)

  35. Coronary Circulation(venous)

  36. Cardiac histology & physiology • Cardiac muscle is made of short, branched fibers • Striated • Uninucleate • There is now some evidence that it has limited mitotic capability (it is likely that regeneration is from migration of stem cells from the blood) • 99% are contractile • 1% are “autorhythmic” or “pacemaker” cells

  37. Cardiac Muscle Tissue

  38. Cardiac Muscle Cells • Intercalated discs: • interconnect cardiac muscle cells • secured by desmosomes • linked by gap junctions • convey force of contraction • propagate action potentials

  39. Characteristics of Cardiac Muscle Cells • Small size • Single, central nucleus • Branching interconnections between cells • Intercalated discs

  40. Cardiac Cells vs. Skeletal Fibers

  41. The intrinsic conduction system • Sinoatrial node: the primary pacemaker – has an intrinsic firing rate of about 100 bpm but kept at 60 – 80 by parasympathetic tone • Generates pacemaker potentials from leakage of Ca++ • Depolarization spreads via gap junctions in intercalated disks • Rate can be adjusted by ANS

  42. Intrinsic conduction system • Signals from SA node travel to the Atrioventricular Node via the internodal pathway • The AV node has its own intrinsic firing rate of 40 – 60 bpm. In absence of SA node function it can establish a “junctional rhythm” that keeps the ventricles working

  43. The conducting pathways • The signal is delayed about 0.1 s and then transmitted down the … • Bundle of His or AV bundle and the left & right bundle branches to the apex • And from there the depolarization is distributed by the Purkinje fibers

  44. Contraction of cardiac muscle fibersand the cardiac cycle • The Electrocardiogram

  45. NSR: Normal Sinus Rhythm

  46. Features of an ECG • P wave: • atria depolarize • QRS complex: • ventricles depolarize • T wave: • ventricles repolarize

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