Gas exchange in fish

Question 1

what is a fishes specialised internal gas exchange surface?

Answer 1

gills

Question 2

what are gills made up of?

Answer 2

gill filaments, they are stacked up in piles

Question 3

what are at right angles to gill filaments and what do they do?

Answer 3

gill lamellae- increase the surface area of gills

Question 4

how do fish take in water?

Answer 4

through the mouth, and forced over the gills and out through an opening on each side of the body

Question 5

what is countercurrent flow?

Answer 5

the flow of water over the gill lamellae and the flow of the blood within them are in opposite directions.

Question 6

what is countercurrent flow important for?

Answer 6

ensuring that the maximum possible gas exchange is achieved

Question 7

through countercurrent flow what percentage of oxygen available in water is absorbed into the blood of the fish?

Answer 7

80%

Question 8

how does countercurrent flow work?

Answer 8

• blood that is already well loaded with oxygen meets water which has it’s maximum concentration of oxygen- DIFFUSION from water to blood takes place
• blood with little or no oxygen meets water that has had most of its oxygen removed, diffusion from WATER TO BLOOD takes place

Question 9

what would happen if the flow of blood and water were in the same direction?

Answer 9

the diffusion gradient would only be maintained across part of the gill lamellae and only 50% of oxygen would be absorbed by the blood