INSECTS

• Tracheal system


  Spiracles, trachea and tracheoles.
• Limiting water loss


  insects have an exoskeleton which is waterproofing which helps reduce water loss. Insects have a small surface area to volume reducing water loss. It also has spiracles that open and close reducing water loss
• Spiracles


  They are small valve like opening that are found across the length of the insects abdomen, they allow O2 and CO2 to enter and leave they also open and close reducing water loss
• Trachea


  these attach to the spiracles they are an internal network of tubes, they have rings within them that keep them open and strengthen them so that gases can move in and out
• Tracheoles 


  Trachea branch into tracheoles, deep into the abdomen of insects. They extend into the tissues ensuring that all the respiring cells get oxygen
• Methods of moving gases into the tracheal system

  1. oxygen is used up by the cells and carbon dioxide is produced this creates a concentration gradient for these gases 2. Mass transport- The muscles in the abdomen contract this forces O2 in and CO2 out, it increases the pressure so that air can move in.
• 3rd method of moving gases into the tracheal system

  when insects are flying their muscles respire anaerobically, this forms lactic acid which is soluble. This reduces the water potential of the cells therefore water moves into the cells via the tracheoles via osmosis. This causes the volume of the tracheoles to decrease, the pressure increases drawing in more air= more air means more gas exchange
• Adaptation for efficient gas exchange

  large number of tracheoles means a larger surface area. The tracheoles are thin therefore it has a short diffusion pathway, The distance between the spiracles and the tracheoles is short so there is a short diffusion pathway. O2 is used up CO2 is made- this creates a concentration gradient