6.3- GAS EXCHANGE IN FISH Flashcards
What is the outer covering of fish like?
waterproof, and so gas-tight
What is the SA:V of fishes like as they are relatively large?
small SA:V
Is the body surface of fishes adequate to supply + remove their respiratory gases?
no
What specialised internal gas exchange surface have fishes evolved?
gills
Where are the gills located in a fish?
within body of fish, behind head
What are the gills made up of?
gill filaments
How are the gill filaments arranged?
stacked up in a pile
What is at right angles to the filaments?
gill lamellae
What does the gill lamellae increase?
increase SA of gills
What happens to water as it taken through the mouth of the fish?
forced over gills + out through opening on each side of body
What is the direction of flow of water over the gill lamellae + flow of blood within them like?
in opposite directions
What is it known as, as the direction of water over the gill lamellae + flow of blood within them is in opposite directions?
countercurrent flow
What is the countercurrent flow important for?
ensuring maximum possible has exchange achieved
What would happen if the water and blood flowed in the same direction in the gill lamella?
far less gas exchange would happen
What is the essential feature of the countercurrent exchange system?
blood + water that flow over gill lamellae do so in opposite directions
What does the countercurrent exchange system mean: blood that’s already well loaded with oxygen?
blood that’s already well loaded with oxygen meets water, which has max concentration of oxygen
so diffusion of oxygen from water to blood happens
What does the countercurrent exchange system mean: blood with little oxygen?
blood with little oxygen meets water which has had most, but not all, of its oxygen removed
so diffusion of oxygen from water to blood happens
What is maintained by the countercurrent exchange system?
diffusion gradient for oxygen uptake maintained across entire width of gill lamellae
As the countercurrent exchange system maintains the diffusion gradient, how much oxygen is absorbed?
about 80% of oxygen available in water absorbed into blood of fish
If the flow of water + blood was in the same direction, what would happen to the diffusion gradient?
diffusion gradient would only be maintained across part of length of gill lamellae
If the flow of water + blood was in the same direction, how much oxygen would be absorbed?
only 50% of available oxygen would be absorbed into blood
