Gas exchange in the tracheal system of insects

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General:

  • Have a tough exoskeleton through which hardly any gaseous exchange can happen
  • Insects blood doesn't have a pigment that carries oxygen
  • The gaseous exchange system of insects has evolved so oxygen is delivered to the cells and removes CO2 in the same way

Why do insects need a transport system?:

  • Multicellular organisms
  • High metabolic rate
  • Low SA:VOL
  • Diffusion wouldn't be quick enough

What features will their exchange surfaces have?:

  • large SA:VOL
  • Thin barrier
  • Selectively permeable

Muscles expand in abdomen:

  • Increase volume
  • Decrease pressure inside
  • Pressure outside > inside
  • Air rushes in

Muscles contract in abdomen:

  • Decrease volume
  • Increase pressure inside
  • Pressure outside < inside
  • Air rushes out

Chitin - fibrous substance, not freely permeable

Tracheole - no chitin, elongated cells

Trachea - hollow tube

End of tracheole is tracheale fluid

Gas exchange:

  • Along the thorax and abdomen are small openings called spiracles
  • Air enters and leaves through these openings, but water is also lost
  • The spiracles can be opened and closed to minimse water loss
  • Behind the spiracles are the trachea - they carry air into the body and are lined with chitin which keeps them open when closed or bent
  • Tracheoles come off the trachea
  • These are smaller and permeable to gases
  • They run between all cells so gas exchange can take place
  • The extent

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