The heart

• Blood flow


  1. superior/inferior vena cava
  2. right atrium -> tricuspid valve
  3. right ventricle -> semi-lunar valve
  4. pulmonary artery -> lungs
  5. pulmonary vein
  6. left atrium -> bicuspid valve
  7. left ventricle -> semi-lunar calve
  8. aorta
• Heart anatomy


  • cardiac muscle
  • chord tendinae - heart strings
  • interventricular septum
  • coronary artery
• Myogenic muscle

  • it can initiate its own contractions within the muscle itself
• Controlling the heart beat

  • Sino-atrial node (SAN) conducts electricity, initiating contraction of the atria
  • Atrio-ventricular node (AVN) delays further contraction, allowing blood to flow into the ventricles
  • bundle of his / purkyne fibres receives the impulse as the ventricles contract
• The cardiac cycle


  • systole - contraction
  • diastole - relaxation
• The cardiac cycle


  • events occur in right and left occur simultaneously
  • three stages

  1. atrial systole
  2. ventricular systole
  3. diastole
• Atrial systole


  1. semi-lunar valves are closed
  2. atrioventricular valves are open
  3. atrial pressure is greater than ventricular pressure
  4. blood is forced into ventricles from the atria
• Ventricular systole


  1. semi-lunar calves are open
  2. atrioventricular valves are closed - due to pressure of contractions, and to prevent back flow into atria
  3. ventricular pressure is greater than atrial pressure
  4. blood is forced into arteries
• Diastole


  1. muscle walls relax
  2. semi-lunar valves close
  3. atrioventricular valves are pushed open by blood
  4. blood flows into atria and into ventricles (gravity)
  5. atrial pressure is greater than ventricular pressure