Blood vessels

• Arteries

  • Carry blood AWAY from the heart
  • Elastic fibres allow them to stretch
  • This helps the vessels withstand the high pressure created by the pumping of the heart
• Veins

  • Carry blood TOWARDS the heart
  • The lumen is wide to allow the low pressure blood to flow through
  • They have valves to ensure the blood flows in the right direction
• Capillaries

  • One cell thick to create short diffusion pathway
  • Permeable walls so substances can move across them