Insects - terrestrial

• System of air tubes to carry oxygen directly to respiring tissue
• Blood supply not used for oxygen transport and no respiratory organs
• Insects small enough for this to be an efficient system - they are invertebrates and don’t need levels of oxygen for respiring that needed to support thermoreregulation
• Air tubes called tracheae - branch into tracheoles which enter muscle cells
• Gas exchange occurs across plasma membranes of tracheoles
• Tracheae opens to outside through series of holes called spiracles
• Spiracles have valves to stop excess evaporation and to aid air flow direction
• Tracheae are made from cuticle with rigid supporting rings of chitin to hold them open
• tracheoles are not thickened or rigid so that diffusion diffusion can occur across the surface - they are thin to penetrate tissue cells
• The Ends of tracheoles are filled with liquid at rest - withdrawn when active
• These tubes are numerous so reach all tissues - short diffusion path from tracheoles to mitochondria to supply oxygen for respiration for nearby muscles
• Many insects need to be light to fly , system or air tubes aids this