structure

• • spiracles lead to the tracheae
  • the tracheae divide into smaller tubes called tracheoles
  • they continue to divide until they penetrate individual body cells
• tracheoles have thin walls

  • this shortens diffusion distance of gases to cells
• tracheoles are highly branched

  • increases surface area for gas exchange
• fluid in the ends of trachea where it joins tissues

  • gas exchange from air to liquid occurs in the tracheoles which allows gases to diffuse to tissues faster
  • tracheal fluid can be withdrawn into the body fluid to increase the surface area of the tracheole exposed to air
• muscles can pump body and force air in and out

  • this maintains concentration gradient for gases
  • this is a type of ventilation
• spiracles can be closed

  • this prevents water loss
• spiracles - tiny pores that allow gases to enter and leave the tracheae