blood

• Red blood cells carry oxygen from the lungs to all the body's cells
• Red blood cells

  • have a biconcave disk shape which gives a large surface area for oxygen absorption
  • no nucleus
  • contain haemoglobin which binds to oxygen in the lungs to form oxyhaemoglobin
  • in body tissues oxyhaemoglobin releases oxygen to cells by splitting haemoglobin + oxygen
• White blood cells defend against infection
• Phagocytosis: the ingestion of bacteria by white blood cells
• White blood cells have a nucleus
• White blood cells fight microorganisms as well as antitoxins to neutralise any toxins produced by microorganisms
• Platelets help blood clot
• Platelets are small fragments of cells which have no nucleus. They help blood clot at a wound.
• Plasma is the liquid that carries everything in blood
• Plasma carries red blood cells, white blood cells, glucose, amino acids, carbon dioxide, urea, hormones, proteins, antibodies, antitoxins and platelets