insects

• • relatively high oxygen requirements.
  • have a tough exoskeleton through which little or no gaseous exchange can take place.
  • no blood pigments that carry oxygen.
• methods of increasing gas exchange

  mechanical ventilation= air is actively pumped into the system by muscular pumping movements of the thorax and abdomen- this changes the volume and pressure in the body.

  collapsible enlarged trachea= increases the amount of air moved through the gas exchange system.
• -air enters and leaves through spiracles, water is also lost.-along the thorax there are small openings= spiracles.

  -spiracles can be opened+ closed by sphincters. (kept closed to prevent water loss)

  -leading away from spiracles are the tracheae= large tubes which carry air into the body.

  -run into and along the body
• -tracheae are lined by spirals of chitin= which keep them open if it's bent or pressed.

  -chitin makes up the cuticle= relatively impermeable to gases.

  -trachea branch to form narrower tubes= tracheoles.

  -each tracheole= is a single, elongated cell with no chitin lining (permeable to gases)- they are small and spread throughout the tissue, running between individual cells= where gas exchange happens.
• -as air moves along the trachea and tracheoles by diffusion.

  -vast number of tracheoles have a large surface area.

  -oxygen dissolves in moisture on the walls of the tracheoles and diffuses into surrounding cells.

  -tracheal fluid= limits the penetration of air for diffusion.

  -when oxygen demands build up- a lactic acid build up results in water moving out of the tracheoles by osmosis.