The Blood

• Blood plasma

  The liquid part of the blood
• Functions of blood plasma

  1. Transports dissolved substances around the body

  2. Transports soluble digestion products from small intestine to other organs

  3. Transports carbon dioxide from body cells to lungs

  4. Transports waste product urea from liver to kidneys
• Red blood cells


  • Contain the oxygen-carrying molecule haemoglobin
  • Have no nucleus, allowing more space for haemoglobin
  • Have a biconcave disk shape for greater surface area
• Function of red blood cells

  Transport oxygen from lungs to body cells
• White blood cells


  • Part of the immune system
  • Contain a nucleus with DNA encoding instructions
• Platelets


  Tiny fragments of cells that help the blood to clot
• Uses of donated blood

  • Replace blood loss during injury
  • Platelets extracted to help clotting
  • Proteins extracted, e.g. antibodies
• Blood transfusion


  Donated blood must be the same blood type as the patient's, otherwise the body's immune system will reject it
• There is a risk of infection from using blood products, but in the UK blood is screened for infection so the risk is extremely low