4.heart

• Thymus gland


  Bilobed structure, attains its greatest size in the neonate, playing a key role in the development of the immune system in early life but continues to grow until puberty and then it undergoes gradual involution in which the thymic tissue is replaced by fat
• Thymus gland size
• Thymosin


  Promotes T lymphocyte differentiation and maturation
• Tissue layer the needle must traverse to reach accumulating blood in cardiac tamponade
• Pericardium


  • Double walled fibro-serous sac
  • Located: ant to T5 – T8 vert; post to body of sternum and 2nd to 6th costal cart
• Layers of pericardium


  • Fibrous
  • Serous (Parietal, Visceral)
• Pericardial cavity


  Contains pericardial fluid (30 ml)
• Cardiac tamponade


  Results from accumulation of fluid in the pericardial cavity that compresses the chambers of the heart – decreased venous return and reduced cardiac output
• Kussmaul sign


  Distention of the veins of the neck on inspiration
• Pericardiocentesis


  1. Needle is passed through the parietal pericardium – site is left xiphocostal angle (enters skin → fascia → rectus sheath → rectus abdominis → fibrous layer → serous layer of parietal pericardium)

  2. Drainage of fluid – left 5th or 6th ICS near the sternum
• Normal heart weight


  • 280 - 340 gms males
  • 230 - 280 gms females
• Heart


  • Double muscular pump
  • Right side – receives deoxygenated blood from body & pumps it into lungs
  • Left side – receives oxygenated blood from lungs & pumps it into aorta
• Coronary artery dominance


  • Right dominance - Posterior interventricular artery is a large branch of the Right Coronary artery (67%)
  • Left dominance - Posterior interventricular artery is a branch of the Circumflex branch of the Left Coronary artery (15%)
  • Codominance - Both the Right coronary and Circumflex arteries contribute to the posterior interventricular artery
• Major coronary veins and accompanying coronary arteries

  • Great Cardiac vein - Anterior Interventricular artery
  • Middle Cardiac vein - Posterior Interventricular artery
  • Small Cardiac vein - Right Marginal artery
• Myocardial infarction


  Localized avascular necrosis of cardiac muscle cells caused by prolonged ischemia
• Occlusion of the circumflex branch of the left coronary artery

  Myocardial infarction in the left atrium and ventricle
• Occlusion of the anterior interventricular branch of the left coronary artery

  Myocardial infarction in the interventricular septum and apex
• Occlusion of the anterior interventricular artery and marginal branch of the right coronary artery

  Myocardial infarction in the right ventricle
• Occlusion of the right coronary artery

  Myocardial infarction in the right atrium
• Angina pectoris


  Chest pain that results from transient ischemia brought on by exertion, reduced blood flow because of narrowing of a coronary artery
• Myocardial infarction


  Sudden, severe pain beneath the sternum, results from localized avascular necrosis of cardiac muscle cells caused by prolonged ischemia
• Angina pectoris


  Tightness/squeezing pain, precipitated by stress/exertion and relieved by rest
• Myocardial infarction


  More severe pain, not relieved by rest
• Sympathetic supply to the heart

  From cervical & upper thoracic portion, increases heart rate & its contraction
• Parasympathetic supply to the heart

  From Vagus nerve, slows heart rate & reduces the force of its contraction
• Lymphatic vessels of the heart receive lymph from the myocardium and epicardium, follow the coronary arteries to drain into mediastinal nodes
• SA node is the pacemaker, located within the atrial wall on the right side of its junction with the SVC
• AV node is located in the interatrial septum superior to the opening of the coronary sinus
• AV bundle/Bundle of His is the membranous portion of the conduction pathway
• Right and left bundle branches are the muscular portion of the interventricular septum
• Purkinje fibers are part of the electrical conduction system of the heart
• V1 ECG lead


  Placed in the 4th intercostal space just to the right of the sternum
• V2 ECG lead


  Placed in the 4th intercostal space just to the left of the sternum
• V3 ECG lead


  Placed midway between V2 and V4
• V4 ECG lead


  Placed in the midclavicular line, 5th intercostal space
• V5 ECG lead


  Placed in the anterior axillary line, 5th intercostal space
• V6 ECG lead


  Placed in the midaxillary line, 5th intercostal space
• ST elevation in leads II, III and aVF on ECG


  Indicates an infarction of the inferior wall
• ST elevation in leads V1 to V3 on ECG

  Indicates an infarction of the anterior wall or anteroseptal region
• The fossa ovalis is seen in the right atrium