blood vessels

• arteries:

  • carry blood away from the heart
  • layers of muscle in the walls make them strong
  • elastic fibers allow them to stretch
  • helps vessel withstand high pressure
  • narrow lumen - high pressure
• veins:

  • carry blood towards the heart
  • thin layers of muscle
  • wide lumen - low pressure
  • valves to prevent back flow of blood
• capillaries:

  • allow blood to flow very close to cells
  • one cell thick walls - short diffusion pathway
  • permeable walls so substances can move across them
• rate of blood flow:

  • rate = volume / number of minutes