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The Heart

The Heart. Cardiology. Physical Characteristics. Situated between the lungs in the mediastinum About the size of a clenched fist Cone or pyramid shape, tilting to the left Apex - inferior portion Base - superior portion. Pericardium - 3 layers. Fibrous pericardium - outer layer

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The Heart

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  1. The Heart Cardiology

  2. Physical Characteristics • Situated between the lungs in the mediastinum • About the size of a clenched fist • Cone or pyramid shape, tilting to the left • Apex - inferior portion • Base - superior portion

  3. Pericardium - 3 layers • Fibrous pericardium - outer layer • Serous pericardium - inner layer • parietal layer • visceral layer (epicardium) • Pericardial cavity - space between the parietal and visceral layers that is filled with pericardial fluid • Pericardial fluid - lubrication,reduces friction

  4. Heart Wall • Epicardium - outermost layer • visceral pericardium • Myocardium - middle layer • cardiac muscle • involuntary, striated, short, branched cells • intercalated discs • Endocardium - inner layer • lines the chambers and covers the valves • simple squamous epithelium

  5. Heart Chambers • Two upper atria ; two lower ventricles • Atria are the receiving chambers • Ventricles are the distributing chambers • Interatrial septum separates atria • Interventricular septum divides ventricles • Auricles are external flaps • Left ventricle very thick

  6. Heart Valves • Atrioventricular valves • tricuspid (right) • bicuspid or mitral (left) • chordae tendineae • papillary muscle • Semilunar valves • aortic semilunar • pulmonary semilunar • three pocketlike cusps

  7. Valve Disorders • Rheumatic Fever - group A, B-hemolytic Streptococcus pyogenes • Heart Mumur • stenosis • incompetent valves • Mitral valve prolapse (MVP)

  8. Blood Flow through the Heart • The heart receives blood from the superior vena cava, inferior vena cava and the coronary sinus • Right atrium->tricuspid valve->right ventricle-> pulmonary semilunar valve-> pulmonary trunk>pulmonary arteries-> lungs-> pulmonary veins->left atrium->mitral valve->left ventricle>aortic semilunar valve -> aorta

  9. Pulmonary & Systemic Circulation • Pulmonary circulation - refers to blood going through the right side of the heart to the lungs • Systemic circulation - involves the left heart. Oxygenated blood from the lungs flows into the left atrium, enters the left ventricle, out through the aorta into the body’s tissue, and back via systemic veins to the right atrium

  10. Coronary Circulation • The aorta branches into the left and right coronary arteries

  11. Blood flow through myocardium • Left coronary artery • Anterior interventricular artery • Circumflex artery • Right coronary artery • Posterior interventricular artery • Marginal artery • Arterial anastomoses

  12. Venous Drainage • Great cardiac veins • Coronary sinus • Right atrium

  13. Cardiac Conduction System • Sinoatrial (SA) node • Pacemaker of the heart • Atrioventricular (AV) node • Atrioventricular bundle (Bundle of His) • Left and right bundle branches • Purkinje fibers • Modification by the ANS and hormones

  14. Cardiac Physiology

  15. Electrocardiogram - ECG • P wave - atrial depolarization • QRS complex - ventricular depolarization • T wave - ventricular repolarization • Atrial repolarization is masked by the larger QRS complex

  16. Arrhythmias Abnormal Heart Rhythms • Heart block - blockage in the AV node • Tachycardia - >100 beats per minute • Bradycardia - <60 beats per minute • Fibrillation - uncoordinated quivering • Flutter - rapid contractions • PVC - premature ventricular contraction • PAC - preatrial contraction

  17. Terms • Myocardial infarction (MI) - heart attack • Infarction - tissue death due to loss of blood supply • Ischemia - decreased blood flow causing hypoxia • Angina pectoralis - chest pain related to coronary problems

  18. Cardiac Cycle • Cardiac cycle consists of one complete cycle of contraction and relaxation • Contraction phase - systole • Relaxation phase - diastole • Complete cycle - 0.8 seconds • Phases : relaxation period, ventricular filling, ventricular systole • Normal heart rate - 75 beats/minute

  19. Cardiac Output • CO = Stroke volume x Heart rate • Amount of blood passing through a ventricle in 1 minute • SV = Amount of blood that is pumped by a ventricle per beat (approx. 70 ml) • HR = number of beats per minute

  20. Examples • Rest - CO = 70ml/beat x 75 beats/min = 5250ml/minute =5.25 liters/minute • Exercise - • CO = 140ml/beat x 150 beats/min = 21,000ml/minute = 21 liters /minute

  21. Factors influencing stroke volume “Frank - Starling law of the heart” • Critical factor = stretch of cardiac muscle • Preload - how much blood enters a ventricle during diastole • Contractility - forcefulness of a contraction • Afterload - pressure needed before ventricle ejection occurs

  22. Cardiovascular Center Medulla Sympathetic nervous system Cardiac accelerator nerves Parasympathetic nervous system Vagus nerve Baroreceptors - monitor pressure aortic arch carotid arteries Chemoreceptors - monitor chemicals aortic/carotid bodies Hormones, age, fitness,gender Regulation of Heart Rate

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