Circulatory system-the heart

• The circulatory system carries food and oxygen to every cell in the body
• The circulatory system also carries waste products to where they can be removed from the body
• Double circulatory system


  Two circuits joined together
• Double circulatory system


  1. Heart pumps deoxygenated blood to the lungs

  2. Blood picks up oxygen in the lungs

  3. Oxygenated blood returns to the heart

  4. Heart pumps oxygenated blood around the body

  5. Deoxygenated blood returns to the heart to be pumped to the lungs
• Circulatory system


  • Made up of the heart, blood vessels and blood
• Heart


  An organ with four chambers, with walls mostly made of muscle tissue used to pump blood around the body
• How the heart pumps blood

  1. Blood flows into the two atria

  2. Atria pump the blood into the ventricles

  3. Ventricles pump the blood out of the heart

  4. Blood from right ventricle goes to lungs

  5. Blood from left ventricle goes to rest of body

  6. Blood flows to organs through arteries, returns through veins

  7. Atria fill again, cycle starts over
• Heart valves


  • Stop the blood flowing backwards
• Heart


  • Needs its own supply of oxygenated blood from coronary arteries
• Pacemaker


  Group of cells in the right atrium wall that control the resting heart rate and tell the heart when to pump blood
• A pacemaker that doesn't work properly causes an irregular heartbeat
• An artificial pacemaker (a small electrical device) can be used to keep the heart beating regularly
• Arteries


  Carry blood under pressure
• Heart pumping blood


  Pumps the blood out
• Arteries


  • Have thick walls
  • Have elastic walls
• Capillaries


  • Are really small
  • Are one cell thick
  • Allow substances to pass in and out
• Veins


  • Take blood back to the heart
  • Have thinner walls than arteries
  • Have valves to help blood flow in the right direction
• Calculating rate of blood flow

  Volume of blood / Number of minutes
• Calculating rate of blood flow

  • 1300 ml of blood in 4 minutes = 325 ml per minute
  • 2.175 litres of blood in 8.7 minutes = 250 ml per minute
• Red blood cells


  Carry oxygen
• White blood cells


  • Defend against infection
  • Can change shape to gobble up microorganisms
  • Produce antibodies and antitoxins
• Platelets


  Help blood to clot and stop bleeding
• Plasma


  Carries red/white blood cells, platelets, food molecules, waste products, hormones
• Blood tests can be used to diagnose many things, not just blood disorders, because blood transports chemicals produced by many organs