blood vessels

• there are 3 types of blood vessel. arteries, veins and capillaries
• the arteries carry blood away form the heart to organs. the blood they hold is bright red oxygenated blood. they stretch as blood is forced through them and return to original shape. humans feel this as a pulse. the blood in arteries is under pressure and is dangerous to cut as blood will spurt out every time a heart beats.
• artery example from above

  
• capillarie from above

  
• the capillary is one cell thick

  • forms a huge network linking arteries and veins
  • blood is under low pressure because high pressure would burst the capillaries
• example of capillary from above

  
• veins carry blood to heart from organs. the blood in the veins are low in oxygen therefore the veins appear as a deep purple colour. has no pulse. valves prevent backflow of blood as there is a low pressure. blood is squeezed back toward the heart
• example of veins from above