Gas exchange in insects

What are some features of an exchange surface?

- Large SA:V ratio

- Thin →short diffusion pathways so diffusion is rapid

- Selectively permeable to allow select materials to cross

- Maintenance of steep concentration gradients

How do insects exchange gases?

They have an internal network of tubes called the tracheal system where respiratory gases move in and out from the spiracles and enter the trachaea down to the tracheoles which carry oxygen directly to respiring cells and remove carbon dioxide.

Why do insects need a tracheal system?

Since their hard exoskeleton made of chitin minimises water loss but is impermeable to gases so the organism's surface is no good for exchange.

What are some features of the tracheal system?

- Tracheae are held open by rings of chitin

- Tracheoles extend throughout the insects body tissues and carry the gases to and away from respiring cells

- There's a short diffusion pathway between the tracheoles and the body cells

How is the movement of gases through the tracheal system caused?

1. Concentration/diffusion gradients

2. Contraction of muscles around the tracheal system

3. Ends of tracheoles are filled with water

What's the point of the ends of tracheoles being filled with water?

So there's a higher water potential in the tracheoles than in the muscle so water would move down a water potential gradient into muscle cells which shorten the diffusion pathway and draw the gases in.