Arteries, veins and capillaries

• Arteries

  Carry very high pressure blood from the heart to the organs in the body
• Arteries

  • Have very thick muscular walls to withstand the very high pressure of the blood
  • Contain elastic fibers that stretch when the surge of blood passes through and then recoil in between the surges to keep the blood moving
• Capillaries

  Where substances such as glucose and oxygen diffuse from the blood to the cells, and carbon dioxide diffuses from the cells back to the blood
• Capillaries

  • Have very thin walls so the diffusion pathway is very short, allowing substances to diffuse rapidly between the blood and the body cells
• Veins

  Carry blood back to the heart
• Veins

  • Have thin walls because the blood pressure is low
  • Contain valves that stop blood flow backwards when the blood is flowing in the correct direction
• The structure of arteries, veins and capillaries relates to their function in the circulatory system