The blood

• Red blood cells: Takes oxygen from the lungs and delivers it through the blood to cells in the body's tissue to be used for cellular respiration

  A) Large surface area which helps to absorb oxygen

  B) Contains haemoglobin which helps to abosrb oxygen and

  C) Bioconcave shape to allow for large surface area

  D) No nucleus to make space for oxygen and haemoglobin

  
• White blood cells:

  • Contain nucleus
  • Contain phagocytes which kill micro-organisms in the blood and perform phagocytosis
  • Contain lymphocytes which produce antibodies and antitoxins
• WBC diagram

  A) Phagocyte

  B) Lymphocyte

  
• Platelets: small fragments of cells with no nucleus
• Platelets:

  • Small fragments of cells
  • No nucleus
  • Helps blood to clot wounds by sealing and clotting wounds when the wall of a blood vessel is damaged
  • Prevents blood cells from being lost
  • Stops micro-organisms entering the blood through the wound
• Diagram

  A) Platelets

  
• Plasma:

  • Straw coloured liquid
  • Makes blood watery so it can flow
  • Carries all cells found in blood
  • Carries glucose and amino acids
  • Carries waste products e.g carbon dioxide and urea
  • Carries hormones,antibodies and antitoxins
• Arteries carry blood away from the heart
• Capillaries exchange nutrients and oxygen with tissues
• Veins carry blood back to the heart
• Arteries:

  • Blood will be at high pressures so arteries need to be strong and elastic
  • so they have a thick layer of muscle to keep them strong and a thick layer of elastic tissue so they can stretch and recoil
• Capillaries:

  • Very small
  • Come into close contact with all cells in the body
  • By exchanging the substances they give our cells useful nutrients and oxygen and take away waste products e.g carbon dioxide
• Adaptations of capillaries:

  • Walls are only one cell thick and permeable so substances can easily diffuse through them
  • Lumen is tiny but because there are so many of them the total cross sectional area is huge so the pressure of blood is much lower than the arteries and flows more slowly giving the blood time to exchange things with the tissues
• Veins are vessels of capillaries that transport blood back to the heart
• Veins:

  • Large
  • Have the biggest lumens of all the blood vessels
  • Contain thin walls with small layers of elastic fibre and smooth muscle
  • The blood they carry is at low pressures so walls don't need to be strong
  • Contain valves to prevent backflow of blood ensuring it always flows towards the heart