The Heart

• Humans have a double circulatory system
• How the double circulatory system works


  1. Right ventricle pumps deoxygenated blood to the lungs

  2. Blood returns to the heart

  3. Left ventricle pumps oxygenated blood around the body

  4. Blood gives up oxygen to body cells and returns to the heart deoxygenated
• The heart


  • Pumping organ that keeps blood flowing around the body
  • Walls mostly made of muscle tissue
  • Has valves to ensure blood flows in the right direction
• How the heart pumps blood

  1. Blood flows into the atria from the veins

  2. Atria contract, pushing blood into the ventricles

  3. Ventricles contract, forcing blood into the pulmonary artery and aorta

  4. Blood flows to organs through arteries and returns through veins

  5. Atria fill again and the cycle repeats
• The heart has its own supply of oxygenated blood from coronary arteries
• Pacemaker


  Group of cells in the right atrium wall that produce an electric impulse to control the resting heart rate
• An artificial pacemaker is a device implanted under the skin with a wire to the heart to keep the heart beating regularly
• The right ventricle pumps deoxygenated blood to the lungs
• Artificial hearts


  • Mechanical devices that pump blood when a person's own heart has failed
  • Usually only used temporarily until a donor heart can be found
  • Less likely to be rejected by the body's immune system than a donor heart
• Artificial heart valves


  • Can be biological (from humans/animals) or mechanical
  • Used to replace damaged or weakened heart valves
• Artificial blood


  • Blood substitutes like saline solutions used to replace lost blood volume
  • Can keep people alive temporarily until they can produce new blood cells or receive a blood transfusion