Blood Vessels

• There are 3 types of blood vessel:

  • arteries - carry blood away from the heart
  • capillaries - involved in exchange of materials at the tissues
  • veins - carry blood to the heart
• Arteries:

  • walls are strong and elastic because of the high pressure that blood is pumped at
  • walls are thick compared to the size of the lumen
  • contain thick layers of muscle to make them strong
  • contain strong elastic fibres to allow them to stretch and spring back
• Lumen

  the hole going down the middle of blood vessels
• Capillaries:

  • very small branches off of arteries
  • carry blood close to every cell in the body to exchange substances with them
  • have permeable walls so substances can diffuse through them
  • supply food and oxygen and take away wastes like carbon dioxide
  • walls are usually only one cell thick to increase the rate of diffusion by decreasing the distance over which it occurs
• Veins:

  • formed from capillaries joining up
  • less thick walls than arteries due to blood being at lower pressure
  • bigger lumen than arteries to help blood flow
  • have valves to help keep blood flowing in the right direction
• Rate of blood flow = volume of blood / number of minutes