insect gaseous exchange

• insects have low SA:V so cannot exchange gases via their external layer
• specialised structures:

  • spiracles = paired holes that run along the side of the body
  • tracheae = branched, chitin lined air tubes
  • tracheoles = smaller tubes that end in the muscle fibres
  • muscle fibres = less than 20um to ensure short diffusion pathway into muscles
• at rest:

  insect relies of diffusion through spiracles, tracheae and tracheoles to take in oxygen and remove carbon dioxide
• during activity/ flight:

  • abdominal movements inflate the tracheae - increasing rate of diffusion
  • fluid in tracheoles moves to muscle fibres - reducing diffusion distance
• larger insects:

  inspiration

  • passive process
  • the elastic fibres of the body segments return to their original shape
• larger insects:

  expiration

  • active process,
  • muscles contract and flatten the body,
  • volume of tracheal system decreases,
  • air is forced out
• discontinuous gas exchange

  • some insects have ability to close spiracles using valves
  • reduces water loss and excess oxygen uptake
  • some have hairs