Insects

• Insects have a system of tubes - the tracheal system - that delivers air deep inside their bodies. Gas exchange occurs by diffusion at the ends of the tracheoles.
• Insects do not use their blood system to transport oxygen.
• Insects do not lose too much water vapour from the gas exchange surface because their gas exchange surface is deep inside the body, and their spiracles can close.
• Insects have tracheae (air tubes) that run through their bodies and end at tiny holes on the body surface called spiracles.
• Tracheal system has no pump so relies on passive movement of oxygen into tissues
• The Tracheal System of an Insect:

  A) Spiracle

  B) Trachea

  C) Tracheoles

  
• Tracheae - Tubes made up of chitin which branch out into tracheoles
• Tracheoles - Thin tubes made up of chitin which end in tiny holes called spiracles
• Spiracles - Holes found all over the body of insects through which air enters or leaves the tracheal system
• Spiracles - Holes on the surface of insects that lead to the tracheal system
• Tracheoles - Thin tubules that end at cells
• Oxygen diffuses through spiracles into tracheae then into tracheoles where it can reach all parts of the body
• Insects have no lungs so they rely solely on diffusion through the tracheal system to get oxygen around the body.
• All insects possess a rigid exoskeleton with a waxy coating that is impermeable to gases.
• Insects have evolved a breathing system that delivers oxygen directly to all the organs and tissues of their bodies.
• A spiracle is an opening in the exoskeleton of an insect which has valves. It allows air to enter the insect and flow into the system of tracheae.
• Tracheae are tubes within the insect respiratory system which lead to tracheoles (narrower tubes). There are rigid rings of chitin that keep the tracheae open.
• A large number of tracheoles run between cells and into the muscle fibres (the site of gas exchange).
• For smaller insects, the tracheal system provides sufficient oxygen via diffusion.
• 𝙑𝙀𝙉𝙏𝙄𝙇𝘼𝙏𝙄𝙊𝙉 𝙄𝙉 𝙄𝙉𝙎𝙀𝘾𝙏𝙎:

  Very active, flying insects need a more rapid supply/intake of oxygen. They create a mass flow of air into the tracheal system by:

  • Closing the spiracles
  • Using abdominal muscles to create a pumping movement for ventilation

  Also, during flight, the fluid found at the narrow ends of the tracheoles is drawn into the respiring muscle so gas diffuses across quicker (due to the diffusion distance being shorter).
• What are spiracles?

  Tiny pores that allow gases to enter and leave the tracheae. They are opened and closed by a valve (like plant stomata but in animals).
• What is the tracheae?

  A large internal network of tubes in insects with supported rings of chitin to prevent them from collapsing.
• What are the tracheoles?

  Tubes that extend from the tracheae throughout all of the body tissues of the insect. They allow atmospheric air to be brought directly to respiring tissues.
• All insects possess a rigid exoskeleton with a waxy coating that is impermeable to gases, so they have evolved a breathing system that delivers oxygen directly to all the organs and tissues of their bodies
• Explain the ways in which an insect’s tracheal system is adapted for efficient gas exchange.

  1. Tracheoles have thin walls so short diffusion distance to cells;
  2. Highly branched so short diffusion distance to cells;
  3. Highly branched so large surface area for gas exchange;
  4. Tracheae provide tubes full of air so fast diffusion into insect tissues;
  5. Fluid in the end of the tracheoles that moves out into tissues during exercise so faster diffusion through the air to the gas exchange surface;
• 𝐋𝐈𝐌𝐈𝐓𝐈𝐍𝐆 𝐖𝐀𝐓𝐄𝐑 𝐋𝐎𝐒𝐒:

  • small SA:V ratio - minimises the area over which water is lost
  • waterproof covering over body surfaces - rigid outer skeleton of chitin with a waterproof cuticle
  • spiracles - can be closed to reduce water loss