Vessels

• Veins characteristics


  -thin outer wall

  -thin layer of muscle+elastic fibres

  -wide lumen

  -low pressure

  -have valves to prevent back flow
• Veins job 


  take blood into heart

  -VeIN -IN heart
• Arteries characteristics


  -thick outerwall

  -thick layer of muscle+elasctic fibres

  -narrow lumen

  -high pressure
• Arteries job 


  take blood away from heart

  -Artery-Away

  carry oxygenated blood to body
• Capillary characteristics 


  -wall one cell thick to allow diffusion

  -thick lumen

  -smallest blood vessels in body
• Capillary job 


  -exchange oxygen, nutrients, waste between blood and cells

  -diffuse across walls
• Why are capillary walls one cell thick? 


  To allow diffusion of oxygen and carbon dioxide