Insect gas exchange system Flashcards
What is the tracheal system?
Specialised system that extends right into the muscle tissues
This allows oxygen to diffuse a relatively short distance into the muscle
System of pipes - connects air outside to tissues that require oxygen
Held open by special bonds of cuticle
What are spiracles?
Small opening through whichever air enters/ exits the insect
Have valves to open and close
What are tracheae
Internal tubes connected to the skittles through which gases travel
Held open with spiral bands of cuticle
What are tracheoles
Fine tubes formed where tracheae branch many times
Tracheal system order
Spiracle -> Trachea -> Tracheole -> Tissues
Why do spiracles have valves?
To open and close and prevent evaporation and water loss
What are the branches of the tracheae called
tracheoles
How is the rate of diffusion maximised in the tracheal system
Many tracheoles - large surface area
Thin - Short diffusion pathway
How is the oxygen concentration gradient created?
There is a higher oxygen concentration outside the insect (where the conc is lower) which then enter the insect through the spiracles and along the trachea and tracheoles
How is the CO2 concentration gradient created
High levels of CO2 cause the spirals to open wider
This increases the movement of air and increases the diffusion rate
How do larger insects uptake oxygen?
active, flying insects need a more rapid supply of oxygen
They create a mass flow of air into the tracheal system
How do larger insects create a mass flow of air into the tracheal system
By closing the spirals
Using abdominal muscles to create a pumping movement for ventilation
How does air leave the tracheae
Body muscles contract, wing muscles relax to compress the tracheae forcing air out of them (expiration)
How does air enter the tracheae (inspiration)
Body muscles relax and wing muscles contract, the tracheae sprint back into shape and oxygen is drawn into them, speeding up the rate of diffusion
—> maintains conc gradient (with expiration)
—> further speeds up exchange
What happens at the ends of the tracheoles when an insect is very active?
Anaerobic respiration - activity
The muscles repsire anaerobically, producing lactic acid
- This decreases the muscle cell water potential
- Water leaves the tips of tracheoles and enters the cells by osmosis
- As water enters the cells from the tracheoles, more air is drawn into the tracheoles providing a bigger surface area for gas exchange within the muscle tissue
This allows oxygen to diffuse in at a faster rate for aerobic respiration
Anaerobic respiration- resting
When activity stops, the lactic acid is oxidised in the muscle cell, returning the water potential to normal
The water potential of the cells is now higher than that in the tracheoles
Now water leaves the cells and re enters the tracheoles by osmosis
- This pushes the stale air with low O2 and high CO2 out towards the spiracles allowing movement of via the spiracle
How is the insect adapted to exchange gases with its environment?
1) Tracheal system connects air in environment to tissues
2) Valves on spiracles reduce loss of water by evaporation
3) Tracheoles have thin walls for short diffusion pathway
4) Tracheoles penetrate all tissues so all cells get oxygen by diffusion
5) Many tracheoles for a large surface area
6) Use of oxygen in respiration provides diffusion concentration gradient
7) Active insects can pump abdominal region to increase amount of fresh air available
