Mechanism of gas exchange in bony fish Flashcards
What are the issues associated with living in water?
- Water is 1000x denser than air
- Water is 100x more viscous than air
- Water has much lower oxygen content than air
What are 2 major adaptations of fish?
Gills + countercurrent mechanism
What are the gills protected by?
Bony flap called operculum, which is involved in maintaining flow of water over gills
What are gill arches arranged in?
Stacks (or gill plates) along length of fish
What does each gill arch contain?
Numerous filaments, which are arranged in stacks
What does each gill filament contain?
Many lamella, which is the main site of gas exchange in bony fish
What are the features of the lamella?
Each lamella has large SA + rich blood supply
Countercurrent flow occurs at lamella
What do cartilaginous fish rely on to maintain flow of water over their gills?
Continuously swimming - called ram ventilation
How do bony fish maintain flow of water over their gills? When opening their mouth
- Mouth opens + floor of buccal cavity lowers
- This increases volume + decreases pressure in buccal cavity
- Water moves into buccal cavity via mouth
- Pressure in opercular cavity higher than in buccal cavity = Opercular valve closes to stop backflow of water
How do bony fish maintain flow of water over their gills? When closing their mouth
- Mouth + operculum closes, sides of opercular cavity move inwards
- Decreases volume of opercular cavity
- Pressure in operculum cavity increases
- Pressure in opercular cavity higher than outside = operculum opens + water flows out of gills
What are the 2 further adaptations to increase effective gas exchange in water/fish?
- Tips of adjacent (neighbouring) gill filaments overlap
- Water moving over gills + blood in gill filaments flow in different directions
What is the result of the tips of adjacent gill filaments overlapping?
Increases resistance to flow of water
More time for gas exchange if water moves slowly over lamellae
What is a countercurrent system?
Water flowing over gill lamella flows in opposite direction to blood flowing through capillaries in lamellae
What does a countercurrent mechanism ensure?
A conc gradient is maintained across whole length of exchange surface
In bony fish, 80-85% of O2 from water
What is a concurrent flow and what is the result?
Where water flows in same direction
Only allows for about 50% of O2 to be extracted from water
Why does a concurrent flow happen?
Because conc gradient isnt maintained + equilibrium is reached quickly
