Gas exchange in insects

• Name three structures in the tracheal system.

  • Spiracles
  • Trachea
  • Tracheoles
• How does the tracheal system provide a large surface area?

  • highly branched tracheoles
  • large number of tracheoles
  • fluid in ends of tracheoles moves into tissues during exercise
• Why are the ends of the tracheoles filled with fluid?

  • Adaptation to increase movement of gases
  • When insect flies and muscles respire anaerobically - lactate produced
  • Water potential of cells lowered, so water moves from tracholes to cells by osmosis
  • Gases diffuse faster in air
• How do insects limit water loss?

  • Small SA:Vol ratio
  • Waterproof exoskeleton
  • Spiracles can open and close to reduce water loss
  • thick waxy cuticle which increases diffusion distance so there is less evaporation
• How do oxygen and carbon dioxide diffuse in/out of the tracheal system?

  Through the spiracles, which are attached to the trachea
• What is the trachea?

  The trachea is a network of internal tubes and the tubes have rings of cartilage within them to strengthen them and keep them open.
• What are the tracheoles?

  The trachea branch into smaller tubes called tracheoles. These extend throughout all the tissues in the insect to deliver oxygen to all respiring cells.
• The tracheoles are the site of gas exchange. What adaptions do they have for efficient gas exchange?

  • Tracheoles have thin walls so short diffusion distance to cells
  • Tracheoles are highly branched, reaching all the cells to provide a short diffusion distance
  • Tracheoles are highly branched providing a large surface area for gas exchange
• How do insects maintain the diffusion gradient during periods of high activity?

  Insects contract and relax their abdominal muscles, which actively moves air in and out of the tracheal system, helping to maintain the diffusion gradient for oxygen and carbon dioxide.
• What happens when an insect respires anaerobically?

  When the insect is very active and respires anaerobically, lactate is produced, which lowers the water potential of muscle cells. This causes water at the ends of the tracheoles to move out of the tracheoles into the cells by osmosis. This reduces the volume of fluid in the tracheoles, so gases diffuse more quickly through air than through liquid, resulting in faster diffusion to the tissues.
• What adaptations do insects have to prevent water loss?

  • Insects have a waterproof exoskeleton to reduce evaporation from their surface.
  • Spiracles (from which gases enter and water evaporates) can open and close to reduce water loss.
  • Spiracles have hairs around them to trap humid air and reduce the water potential gradient, reducing evaporation.
• How is the tracheal system adapted for efficient gas exchange?

  Insects have a tracheal system for gas exchange. They have large numbers of fine tracheoles to provide a large surface area, the walls of tracheoles are thin to provide a short diffusion pathway and the use of oxygen and production of carbon dioxide sets up steep diffusion gradients.