the heart

• Humans have a double circulatory system where deoxygenated blood is pumped from the heart to the lungs, becomes oxygenated, and then returns to the heart to be pumped to the organs
• The benefit of the double circulatory system is that the blood passes through the heart twice, allowing it to travel rapidly to the body cells and deliver the oxygen they need
• Heart


  • Organ consisting mainly of muscle tissue
  • Job is to pump blood around the body
• Chambers of the heart

  • Left atrium
  • Right atrium
  • Left ventricle
  • Right ventricle
• The atria are separated from the ventricles by valves
• Main blood vessels entering and leaving the heart


  • Vena cava (brings in deoxygenated blood from the body)
  • Pulmonary artery (blood passes from heart to lungs)
  • Pulmonary vein (oxygenated blood passes from lungs to heart)
  • Aorta (blood is pumped from heart to body)
• Pattern of blood flow through the heart

  1. Blood enters left and right atria

  2. Atria contract, forcing blood into ventricles

  3. Ventricles contract, forcing blood out of heart

  4. Valves prevent backflow into atria
• Left ventricle


  • Has thicker muscular wall than right ventricle
  • Pumps blood around entire body, so needs greater force
• Right ventricle


  • Only pumps blood to the lungs
• Coronary arteries


  • Branch out of the aorta and spread into the heart muscle
  • Purpose is to supply oxygen to the muscle cells of the heart
• Pacemaker


  Group of cells found in the right atrium that control the natural resting heart rate
• If the pacemaker stops working correctly, doctors can implant an artificial pacemaker to correct irregularities in the heart rate
• Left Ventricle


  One of the four chambers of the heart, responsible for pumping oxygenated blood from the lungs to the entire body.
• Thicker Muscular Wall


  Comparing the left and right ventricles, the left ventricle has a more robust and thicker muscular wall.
• Right Ventricle


  The other chamber of the heart, responsible for pumping deoxygenated blood from the body to the lungs, with a thinner muscular wall.
• Needs Greater Force


  Why the left ventricle has a thicker muscular wall: it pumps blood around the entire body, requiring more force and energy.
• Aorta


  A large artery that arises from the left ventricle of the heart, distributing oxygenated blood to various parts of the body.
• Pulmonary Arteries


  Arteries that arise from the right ventricle of the heart, transporting deoxygenated blood from the heart to the lungs for oxygenation.