Respiratory System of Insects Flashcards
What are the two main components of the respiratory system of an insect?
- Spiracles
2. Trachea
What are spiracles?
External openings, hypothetically one per segment
Where do spiracles usually occur?
On the Mesothorax, Metathorax, and abdominal segments (1-8)
What are trachea?
Series of air-filled tubes unique to insects that are entirely separate from the circulatory system.
- Excessively branched
What are trachea lined with?
lined with cuticle
What are tracheal trunks?
Logitudinal tubes connected to the main tubes from the spiracles
What are Taenidia?
Spiral circular thickening running through trachea
What is the function of the taenidia?
prevents tubes from collapsing under reduced pressure
What are tracheoles?
smallest diameter tubes that cover most of the insects body, even extending between muscle fibres
When are tracheoles fluid filled?
At rest
When are tracheoles air filled? why?
during activity for maximum gas diffusion
What are two types of ventilation in insects?
Passive and active
What insects might use passive ventilation?
Smaller insects
What is passive ventilation?
The simple diffusion of O2 and CO2 controlled by spiracles
What happens during passive ventilation?
- Continuous O2 uptake and CO2 storage to create suction
- CO2 is expelled in cylindrical bursts and stored in the hemolympth as bicarbonate in between creating negative pressure -> air gets sucked into trachea
- When CO2 conc. in trachea is greater than 6.5%, the spiracles relax and CO2 is released
Which insects might use active ventilation? why?
Large insects - they need to physically move air in and out of their tracheal system
How is active ventilation performed?
- Close forward spiracles and force air out of rear ones via blood pressure or muscle contraction in order to create negative pressure up front when rear spiracles closed
- Close rear spiracles in order to suck air into front spiracles
What is the purpose of the tracheal air sac in flying insects?
Can increase tidal flow, reduce density of the insect and can provide room for egg development