Cardiovascular system

• Cardiovascular system


  The system responsible for circulating blood throughout the body
• The heart


  • Beats 100,000 times per day
  • Pushes 7,000 litres of blood through our body every 24-hours
• Heart chambers


  • 2 atria which receive blood
  • 2 ventricles which discharge blood

  
• Heart valves


  • Aortic valve: left ventricle to aorta
  • Mitral valve: left atria to left ventricle
  • Tricuspid valve: right atria to right ventricle
  • Pulmonary valve: right ventricle to pulmonary artery

  
• Heart sounds are described as lub-DUB
• Heart wall layers


  • Endocardium: thin layer lining heart chambers and valves
  • Myocardium: involuntary striated muscle making up bulk of heart
  • Epicardium: outer layer of mesothelial cells
  • Pericardium: thin fibrous sheath enclosing heart with lubricating interstitial fluid

  
• Heart beat


  1. Diastole: atria and ventricles relax and fill with blood

  2. Systole: atria contract and push blood into ventricles, then ventricles contract and pump blood out

  
• Heart's electrical system


  • Sinoatrial node (heart pacemaker)
  • Atrioventricular node (gate)
  • Bundle of His & Purkinje fibres

  
• Electrical impulses coordinate heart activity


  1. Atria contract, blood pumped into ventricles

  2. Signal slowed at AV node

  3. Ventricles contract, blood into aorta & pulmonary artery

  
• Blood vessels


  • Arteries carry oxygenated blood away from heart
  • Capillaries connect arterioles to venules, allow exchange
  • Veins carry deoxygenated blood back to heart
• Blood pressure


  • Systolic: 120 mmHg
  • Diastolic: 80 mmHg
  • Arteriole: 65 mmHg
  • Capillaries: 25 mmHg
  • Venous: 15 mmHg
  • Vena cava: close to 0 mmHg (CVP)

  
• Pulmonary circulation


  • Shorter than systemic circulation
  • Pulmonary artery pressure: 20/15 mmHg
• Coronary circulation


  • Heart supplied by left and right coronary arteries
  • Cardiac muscle has extensive capillary system
  • Blood returned to right atrium via coronary sinus
  • Left ventricle mostly supplied by left coronary artery

  
• During systole, contraction of ventricles compresses coronary arteries and suppresses blood flow, so >85% of left ventricular perfusion occurs during diastole