blood vessels

• Circulatory System

  Blood Vessels
• Blood Vessels

  • Designed for their function
• Blood flow


  Vessels carry blood to the heart
• Arteries


  • Carry blood under pressure
  • Walls are strong and elastic
  • Contain thick layers of muscle to make them strong and elastic to allow them to stretch and spring back
• Capillaries


  • One cell thick
  • Very small lumen
  • Nucleus of cell
  • Branch off from arteries
  • Carry blood very close to cells
  • Small enough for substances to diffuse in and out
• Capillary walls


  Thin to increase rate of diffusion
• Veins


  • Take blood back to the heart
  • Blood is at lower pressure so walls don't need to be as thick
  • Have a bigger lumen than arteries to help blood flow despite lower pressure
  • Have valves to help keep blood flowing in the right direction
  • Have elastic tissue and smooth muscle
• Calculating rate of blood flow

  Volume of blood / Number of minutes