insects

• insects have tiny air-filled pipes called tracheae which they use for gas exchange
• air moves into the tracheae through pores on the surface called spiracles
• oxygen travels down the concentration gradient towards the cells
• the tracheae branch off into smaller tracheoles which have thin, permeable walls and go into individual cells. oxygen diffuses directly into the respiring cells from the tracheoles
• carbon dioxide from the cells moves down its own concentration gradient towards the spiracles to be released into the atmosphere
• insects use rhythmic abdominal movements to move air in and out of the spiracles
• spiracles - tiny holes able to let air enter the body and prevent water loss. they're controlled by specialised muscles to be opened or closed. spiracles are used to pass air to the trachea
• trachea - a tube lined with chitin, which branches into smaller tubes known as tracheoles
• tracheoles - they deliver oxygen to the cells and tissues of the insect
• chitin - impermeable rings which work to stop structures collapsing. stops diffusion out of the trachea as impermeable
• pathway of oxygen in tracheal system

  1. air enters into the body of the insect through spiracles
  2. spiracles transfer air to the thin tubes called the tracheae
  3. the tracheal system contains a special fluid for carrying oxygen
• water builds up at the bottom of the tracheoles causing slower diffusion. to remove this, lactic acid begins to build up in the cells (anaerobic respiration), decreasing their water potential, where water can move back into the cells
• tracheoles have thin walls so a short diffusion pathway
• there's a large number of tracheoles so there's a large surface area for gas exchange