Ventilation in insects Flashcards
What is the exoskeleton? Can gases be exchanged through the exoskeleton?
External skeleton of insects.
Little to no gas exchange can take place through it
What are spiracles?
Small openings along the thorax and abdomen of insects
What is lost when air moves through spiracles?
Water
What closes and opens spiracles?
Sphincters
Why are spiracle sphincters kept closed as much as possible?
To minimise water loss
When will spiracles be closed?
When insect is inactive and has low oxygen demands
When will spiracles be open?
When insect is active and has high oxygen demands and high CO2 levels
What leads away from the spiracles?
Tracheae
What is the structure of tracheae? What is their function?
Largest tubes of insect respiratory system, 1mm in diameter.
Carry air into body.
Where can tracheae be found?
Inside + along the insect body
What are tracheae lined with?
Chitin
What is the function of chitin?
Keep tracheae open when they’re bent
Why does little gas exchange occur in the tracheae?
It’s made up of chitin, which is an impermeable gas
What do tracheae branch into?
Tracheoles, 0.6-0.8 microns
What is the structure of tracheoles?
Single, elongated cell with no chitin lining - freely permeable
Where does most of the gas exchange in insects occur?
In tracheoles
In most insects, how does air move through their body?
By diffusion, along tracheae and tracheoles
Why do tracheoles enable efficient gas exchange?
Provide a large SA
How does oxygen enter insect cells?
Oxygen dissolves in moisture on tracheole walls + diffuses into surrounding cells
What is tracheal fluid?
Fluid found at end of tracheoles
What is the function of tracheal fluid?
Helps control SA for gas exchange and water loss
What happens when oxygen demands in an insect build up?
Lactic acid builds up + water moves out of tracheoles by osmosis
What system supplies all insect oxygen needs?
Tracheal system
What is the extent of gas exchange in insects controlled by?
Spiracles opening and closing
What are the 2 alternative methods larger insects have to increase gas exchange?
- Mechanical ventilation of tracheal system
2. Collapsible enlarged trachea/air sacs, which act as air reservoirs
How does mechanical ventilation of the tracheal system increase gas exchange in larger insects?
- Air is actively pumped -> tracheal system by muscular pumping movements of thorax + abdomen
- These movements change volume of body + change pressure in tracheoles and tracheae
- Air is drawn into tracheae and tracheoles / forced out as pressure changes
How do collapsible enlarged tracheae/air sacs, which act as air reservoirs, act as an alternative method of increasing gas exchange in larger insects?
The enlarged tracheae increase amount of air moving through gas exchange system.
They’re usually inflated + deflated by ventilating movements of thorax + abdomen
