Circulatory system- blood vessels

• Arteries


  Carry blood away from heart
• Capillaries 


  Exchange of materials at tissues
• Veins 


  Carry blood to the heart
• arteries

  • pumped at high pressure walls strong and elastic
  • walls thick and small lumen
  • layers of muscle and elastic fibers to stretch and spring back
• Capillaries

  • arteries branch into capillaries
  • really tiny
  • carry blood really close to every cell to exchange substances
  • have permeable walls so substances can diffuse in and out
  • they supply food and oxygen and take away waste like CO2
  • walls one cell thick this increases diffusion rate by decreasing distance to occur
• Veins

  • at lower pressure do walls arent as thick
  • bigger lumen to help bloody flow
  • have valves to help prevent back flow of blood
• Rate of blood flow = volume of blood/ number of minutes