circulation

• Transport system


  Vital to carry substance from and to where its needed, supplies body cells with glucose and oxygen from respiration, removes waste materials
• Components of the circulatory system

  • Blood vessels
  • Heart
  • Blood
• Blood vessels


  • Tubes that carry blood around body
• Heart


  • Pumps blood around body
• Blood


  • Liquid that carries substances around body
• Double circulation

  Two transport systems, one carries blood from heart to lungs and back, the other carries blood to all other organs of body and back again to heart
• Arteries


  • Carry blood away from heart to organs
• Veins

  • Blood returns to heart
• Capillaries


  • Tiny vessels that link arteries and veins, enable oxygen and glucose to easily diffuse out of blood into cells
• Walls of heart


  Mostly muscle, supplied with oxygen by coronary arteries
• Two sides of heart

  Fill and empty at the same time = strong and coordinated heartbeat
• How the heart works

  1. Blood enters top chambers (atria)

  2. Right atrium receives deoxygenated blood from body

  3. Left atrium receives oxygenated blood from lungs

  4. Atria contract to force blood down into ventricles

  5. Valves close to stop blood flowing back out

  6. Ventricles contract to force blood out of heart

  7. Right ventricle forces deoxygenated blood to lungs

  8. Left ventricle forces oxygenated blood to rest of body

  9. Valves close to stop blood flowing back in
• Pacemaker


  In right atrium, produces regular electrical signals that spreads through the heart and makes it contract
• Artificial pacemakers


  Solve problems with rhythm of heart, help heartbeat regularly if it has problems
• Artificial hearts


  Used when people waiting for a heart transplant, giving a diseased heart a break
• Arteries


  • Carry oxygenated blood, stretch as blood goes through them, have thick walls, very dangerous if cut
• Veins


  • Carry deoxygenated blood, don't have pulse, have thin walls and valves to prevent backflow
• Coronary arteries


  Supply blood to heart muscle, narrow as you age and fat could build up = coronary heart disease
• Stents


  Metal mesh that help hold up the size of narrowed blood vessels
• Leaky valves


  Heart doesn't work well = breathless
• Blood plasma


  Yellow liquid that carries red blood cells, white blood cells, platelets, dissolved substances
• Red blood cells


  • Biconcave discs to increase surface area, lots of haemoglobin to carry oxygen, no nucleus
• White blood cells


  • Bigger than red blood cells, fewer, have nucleus, part of body's defence system
• Platelets


  • Small fragments of cells, no nucleus, help blood clot at a wound
• Blood clotting


  Series of enzyme-controlled reactions that result in the change of fibrinogen into fibrin, produces a network of protein fibres that capture red blood cells and platelets to form a clot
• Blood groups


  Different number of antigens on the surface of red blood cells
• ABO blood group system

  • A
  • B
  • AB
  • O
• Antigen on red blood cells
• Antibody in plasma
• If blood from different blood groups were to be mixed, it would cause a reaction between the antigen and the complementary antibody, resulting in red blood cells agglutinating (sticking together), which means they cannot work together and can clog up capillaries or larger vessels