Blood vessels

• Arteries


  • Carry blood away from the heart
  • Have strong and elastic walls
  • Have thick layers of muscle to make them strong
• Capillaries


  • Involved in the exchange of materials at tissues
  • Really small
  • Carry blood very close to every cell to exchange substances
  • Have permeable walls so substances can diffuse in and out
  • Supply food and oxygen
  • Remove waste
• Veins


  • Carry blood to the heart
  • Have thinner walls than arteries as they don't need to withstand high pressure
  • Have valves to keep blood flowing in the correct direction
  • Have a larger lumen than arteries to help slow the flow of blood
• Capillaries join up to form veins
• Blood flows at a lower pressure in veins compared to arteries
• The rate of blood flow is slower in veins compared to arteries