Mechanism of gas exchange in insects Flashcards
What does an insects tough exoskeleton do?
Prevents water loss + a barrier to gas exchange
What is along the thorax + abdomen and what is its function?
Spiracles = Allow gases to enter + leave, increases water loss
How is water loss decreased in the spiracles?
Insects can open + close their spiracles using spiracle sphincters to reduce this
What happens to the spiracles when O2 demand is low vs when its high?
O2 demand low = Spiracles closed
O2 demand high = Spiracles open
Where do the spiracles lead to + what are they lined with to prevent?
Leads to tracheae
Lined with chitin, which prevents tubes collapsing on themselves but also impermeable to gases
What does the tracheae subdivide into?
Tracheoles, with diameter of 0.6-0.8um
Each tracheole is a single, elongated cell with no chitin, therefore permeable to gases
Where most gas exchange occurs in insects
What does a large number of tracheoles cause?
Covers huge surface area - means diffusion alone can deliver + remove gases to all cells
What happens as oxygen arrives in the tracheoles?
It dissolves into fluid on surface of cells
Can diffuse into surrounding cells
What is towards the end of each tracheole?
Tracheal fluid, limits amount of air contributing to diffusion
What happens during periods of high oxygen demand?
Lactic acid builds up between tissues
Reduces water potential + water moves via osmosis from tracheal fluid into tissue
This removes fluid from tracheoles + increases SA for diffusion
What are the 2 alternative methods for increasing level of gas exchange in large insects?
Mechanical ventilation, collapsible enlarged tracheae/air sacs
What is mechanical ventilation?
Air is actively pumped into tracheal system by muscular contractions of thorax + abdomen
These movements change vol + pressure in tracheae + tracheoles, causing air to be drawn in + forced out of tracheal system
What are collapsible enlarged tracheae/air sacs?
Act as air reservoirs to increase amount of air moved through tracheal system
Can be inflated + deflated by abdominal + thoracic pumping movements
