Insects

• In insects spiracles are normally found on the thorax and abdomen
• The exoskeleton is impermeable
• There are valves that can open and close the spiracles, this regulates gas exchanges and reduces water loss
• The gas is carried by the trachea, which splits into tracheoles
• Tracheoles carry gases directly into muscles
• Some larger insects are specialised with pigments that help carry oxygen around the insect. These increase efficiency
• To increase the concentration gradient, insect have:

  • Abdominal muscles that can act as a diaphragm, it changes the internal pressure as they contract and relax
  • Moving in certain ways allows more gas to be drawn in
  • Flight muscles also facilitate diffusion by compressing
• The adaptations that help insects exchange more gas all increase the concentration gradient
• As the cells are constantly respiring, there is always some concentration gradient present, allowing for the flow of gas exchange
• Parts of the insect gas exchange system:

  A) Exoskeleton

  B) Trachea

  C) Tracheoles

  D) Muscle cell

  E) Air sac

  F) Spiracle