gas exchange in insects

• Role of chitin in insect tracheae?

  Keep tracheae open if they are bent or pressed
• Why is it hard for insects to exchange gases?

  Tough exoskeleton which means little or no gaseous exchange can take place
• What provides a large surface area for gas exchange in insects?

  • Many tracheoles
  • Small size allows for a large SA:V ratio
• How does the insect overcome the lack of diffusion that occurs sometimes because of tracheal fluid?

  • Tracheal fluid limits penetration of air for diffusion
  • But as oxygen demands increase lactic acid builds up
  • Causing water to move out of tracheoles by osmosis
  • Exposes more surface area for gas exchange
• Alternative methods of increasing gaseous exchange in insects?

  • Mechanical ventilation- air actively pumped into system by muscular pumping of the thorax, air drawn in or forced out of the tracheoles
  • Collapsible enlarged tracheae or air sacs- air reservoirs, increases amount of air moved through the gas exchange system
  • used in insects with a higher metabolic demand
• what are two other organisms with different gaseous exchange systems to mammals?

  • bony fish
  • insects
• true or false? Insects have blood pigments that carry oxygen

  FALSE
• true or false? the gas exchange system of insects allows oxygen to be delivered directly to body cells

  TRUE
• how does air and water enter and leave the body of an insect?

  through spiracles
• what helps open or close spiracles?

  • sphincters
  • to minimise loss of water despite a need for gaseous exchange
• when are spiracles closed in insects?

  when they are inactive and oxygen demands are low
• describe the development of the gaseous exchange system of insects beyond the spiracles



  • leading away from the spiracles are the tracheae
  • run along the insect
  • lined with chitin for support (impermeable to gases so little gas exchange happens in the tracheae)
  • divide further into tracheoles
  • no chitin, gas exchange takes place
  • tracheal fluid at the end of tracheoles

  A) spiracle

  B) tracheae

  C) tracheoles