Heart Anatomy and Physiology:Review


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Heart Anatomy and Physiology:Review

  1. 1. The Cardiovascular System A Review: The Heart
  2. 2. Heart <ul><li>A hollow muscular organ </li></ul><ul><li>Located in thorax between 2 lungs </li></ul><ul><li>4 chambers </li></ul><ul><li>4 valves </li></ul><ul><li>2 atria (atrium) & 2 ventricles </li></ul><ul><li>2 separate pumps (R & L sides) </li></ul><ul><li>Right side receives blood from the body and sends it to the lungs ( pulmonary ) </li></ul><ul><li>Left side receives blood from lungs and sends it to the body ( systemic ) </li></ul>
  3. 3. <ul><li>The heart lies between the lungs in a region called the mediastinum.  You can also see that the heart is wrapped by some membranes that also hold the heart in its position relative to the diaphragm and lungs. </li></ul>
  4. 4. Position of Heart
  5. 5. 2 Pumps
  6. 7. <ul><li>The Pericardium </li></ul><ul><li>The pericardium is the set of membranes around the heart.  It is actually composed of three layers of membranes. </li></ul><ul><li>visceral pericardium - the innermost </li></ul><ul><li>parietal pericardium - the middle, </li></ul><ul><li>fibrous pericardium - the outer one is the extra one, and  is tough.  </li></ul><ul><li>Pericardial Cavity- tiny space between the visceral pericardium and the parietal pericardium   </li></ul>
  7. 8. Layers of the Heart Pericardium Myocardium Fibrous pericardium Serous pericardium (parietal layer) Pericardial space Serous pericardium (visceral layer - Epicardium) Endocardium
  8. 9. Chambers of the Heart
  9. 10. Valves of the Heart <ul><li>4 valves </li></ul><ul><li>One way flow </li></ul><ul><li>Leaky valve = heart murmur </li></ul><ul><li>2 atrioventricular valves </li></ul><ul><ul><li>Left AV valve- bicuspid or mitral </li></ul></ul><ul><ul><li>Right AV valve- tricuspid </li></ul></ul><ul><li>2 semilunar valves </li></ul><ul><ul><li>Pulmonic semilunar valve </li></ul></ul><ul><ul><li>Aortic semilunar valve </li></ul></ul>
  10. 11. Valves of the Heart Tricuspid Valve Mitral Valve Pulmonic Valve Aortic Valve
  11. 12. Atrioventricular Valves <ul><li>Right AV valve </li></ul><ul><li>Between right atrium and right ventricle </li></ul><ul><li>Also called the tricuspid valve because it has three cusps . </li></ul><ul><li>Cusps close when right ventricle contracts….preventing blood from going back up into the right atrium </li></ul><ul><li>Left AV valve </li></ul><ul><li>Between the left atrium and the left ventricle </li></ul><ul><li>Also called the bicuspid valve because it only has two cusps </li></ul><ul><li>Also called the mitral valve </li></ul><ul><li>Cusps close when left ventricle contracts….preventing blood from back up into the left atrium </li></ul>
  12. 13. Semilunar Valves <ul><li>Pulmonary semilunar valve </li></ul><ul><li>When right ventricle contracts, blood is forced through this valve to enter pulmonary trunk </li></ul><ul><li>Aortic semilunar valve </li></ul><ul><li>When left ventricle contracts, blood is forced through this valve to enter the aorta </li></ul>
  13. 14. Cardiac Conduction System <ul><li>The cardiac conduction system generates and transmits impulses that stimulate contraction of the myocardium. </li></ul><ul><li>Under normal circumstances, the conduction system first stimulate the contraction of the atria and then the ventricles. </li></ul>
  14. 15. <ul><li>Electrophysiologic Properties of the Heart </li></ul><ul><li>Excitability . The ability of the heart to depolarize in response to a stimulus. Once stimulated, the whole heart muscle contracts. It is influenced by hormones, electrolytes, nutrition, oxygen supply, medications, infection, and nerve characteristics. </li></ul><ul><li>Automaticity/Rhythmicity. The ability of cardiac cells to initiate an impulse spontaneously and repetitively, without external neurohormonal control. </li></ul><ul><li>Conductivity . The ability of the heart muscle fibers to propagate electrical impulses along and across cell membranes. </li></ul>
  15. 16. Conduction System of the Heart
  16. 18. Coronary Arteries Atherosclerosis is an accumulation of fat on the inner walls of arteries. When coronary arteries become partially blocked…. angina When coronary arteries become significantly blocked…. myocardial infarction
  17. 19. Cardiac Cycle- refers to the events of one complete heart beat. The length of the cardiac cycle is usually about 0.8 sec. <ul><li>Systole (contraction of the muscle)- there is ventricular pumping, the chambers of the heart become smaller as the blood is ejected. Occurs secondary to depolarization of cells </li></ul><ul><li>Diastole (relaxation of the muscle)- there is ventricular filling, the heart chambers fill with blood in preparation for subsequent ejection. </li></ul>
  18. 20. Cardiac Output <ul><li>Volume of blood ejected per minute </li></ul><ul><ul><li>Each ventricle ejects approximately 70mL of blood/ beat </li></ul></ul><ul><li>Averages between 4-8L/min </li></ul><ul><li>CO = Stroke volume X heart rate </li></ul><ul><li>=70 ml X 60 beats/min </li></ul><ul><li>=4,200 ml/min </li></ul>
  19. 21. Stroke Volume Is Determined By Three Factors <ul><li>Preload </li></ul><ul><li>Afterload </li></ul><ul><li>Contractility </li></ul>
  20. 22. Preload <ul><li>Degree of stretch of myocardial fibers </li></ul><ul><li>Determined by the volume of blood in left ventricle (LV) at end of diastole </li></ul><ul><li>Increased volume – increased preload- increased cardiac output (CO) </li></ul><ul><li>Decreased volume – decreased preload – decreased cardiac output (CO) </li></ul>Frank- Starling Law -the critical factor controlling stroke volume is how much the cardiac muscle cells are stretched just before the contract. The more they are stretched, the stronger the contraction will be. The important factor stretching the heart muscles is the venous return.
  21. 23. Factors Which Increase Preload <ul><li>IV fluids </li></ul><ul><li>Blood </li></ul><ul><li>Vasoconstriction </li></ul>
  22. 24. Factors Which Decrease Preload <ul><li>Diuretics </li></ul><ul><li>Dehydration </li></ul><ul><li>Hemorrhage </li></ul><ul><li>Vasodilation </li></ul>
  23. 25. Afterload <ul><li>Resistance or pressure the ventricles must overcome to pump blood out </li></ul><ul><li>Left ventricle (LV) affected by systemic vascular resistance (SVR) </li></ul><ul><li>Right ventricle (RV) affected by pulmonary vascular resistance (PVR) </li></ul><ul><li>Related to arterial pressure or diameter of arteries </li></ul><ul><li>As pressure increases, resistance increases, afterload increases </li></ul><ul><li>As pressure decreases, resistance decreases, afterload decreases </li></ul>
  24. 26. Contractility <ul><li>Force generated by the myocardium when it contracts – inotropic property </li></ul><ul><li>Ejection fraction (EF) - percentage of LV end-diastolic volume that is ejected with each contraction </li></ul>
  25. 27. Autonomic Nervous System (ANS) Regulation of Cardiovascular System <ul><li>Heart rate – chronotropic effect </li></ul><ul><li>Contractility – inotropic effect </li></ul><ul><li>Conduction velocity at AV node – dromotropic effect </li></ul><ul><li>Afterload - vascular resistance – arterial vasoconstriction and dilation </li></ul><ul><li>Preload – venous constriction and dilation </li></ul>
  26. 28. Subdivisions of ANS <ul><li>Parasympathetic – acetylcholine produces inhibitory response </li></ul><ul><li>Sympathetic – catecholamines stimulate </li></ul><ul><ul><li>Increase heart rate – Beta 1 receptors </li></ul></ul><ul><ul><li>Dilate smooth muscles – Beta 2 receptors </li></ul></ul><ul><ul><li>Vasoconstrict vessels – Alpha receptors </li></ul></ul>
  27. 29. The Fetal Circulation