animal transport

• arteries:

  • smooth lining for unrestricted flow
  • thick outer walls that protect high pressure blood flow against leaks
  • narrow lumen: maintains high blood pressure
  • thick layer of muscles and fibre to respond to the rhythmic changes in the blood pressure
• vein:

  • large lumen: allows lower pressure blood to flow easily
  • thin outer layer as lower blood pressure needs less protection
  • valves to ensure that the blood only flows in one direction
• capillaries:

  • only one cell thick: allows for efficient gas exchange
  • very small lumen
  • thin layer of muscle
  • wide enough for cells to squeeze through in a single file