Circulatory system - the heart

• Double circulatory system

  • first circuit - right ventricle pumps deoxygenated blood to the lungs to take in O2. Then returns to the heart
  • second circuit - left ventricle pumps oxygenated blood around the organs of the body. The blood gives up its oxygen to the cells and muscles and deoxygenated blood returns to the heart
• Heart Contracts

  1. blood flows into the 2 atria from the vena cava and the pulmonary vein
  2. atria contracts, pushing the blood into the ventricles
  3. ventricles contract forcing blood into the the pulmonary artery and the aorta
  4. blood then flows to the organs through arteries and returns through veins
  5. atria fills again and the whole cycle starts over
• the hearts pacemaker - controlled by a group of cells in the right atrium wall that acts as a pacemaker, these cells produce a small electric impulse which spreads to the surrounding muscles