Blood vessels

• Blood vessels:

  Arteries : carry out blood away from the heart

  capillaries : exchange of materials at the tissue

  veins :these carry the blood to the heart
• Arteries:

  • artery walls are strong and elastic because the heart pumps the blood out at high pressure
  • the elastic fibers allow arteries to expand
  • the walls are thick because they contain thick layer of muscles to make them strong
  • The largest artery is the aorta
• capillaries :

  • capillaries are tiny
  • they carry the blood really close to every cell in the body to exchange substances with them
  • they have permeable walls so substances can diffuse in and out
  • they supply food and oxygen
  • they take away co2
  • their walls are one cell thick
• veins :

  • take blood back to heart
  • the blood is at lower pressure in the veins
  • they have valves to keep blood flowing in right direction
  • the largest vein is the vena cava