Blood

• Arteries

  
  

  Carry oxygenated blood away from heart

  Small lumen - high blood pressure

  Thick walls with muscle and elastic fibres to force the blood around
• Veins

  
  

  Carry deoxygenated blood towards the heart

  Low pressure - no pulse, valves to stop blood flowing backwards,

  Thin walls and large lumen
• Capillaries

  
  

  Link arteries and veins

  Very narrow and have thin walls - optimise diffusion
• Plasma

  
  

  Transports all blood cells and other things:

  Carbon dioxide to lungs

  Urea to kidneys

  Soluble products of digestion
• Red blood cells

  
  

  Biconcave discs - increased surface area

  Haemoglobin to carry oxygen

  No nucleus to carry more oxygen
• White blood cells

  Involved in the immune response to fight pathogens