3.2.2 Gas Exchange In Bony Fish

Question 1

Explain how counter current flow works

Answer 1

Blood and water flowing in opposite directions, no equilibrium is reached so there will always be more oxygen in water than in blood. Diffusion of oxygen occurs across the entire length of the gill plate.

Question 2

Why is counter current flow more efficient than parallel flow

Answer 2

No equilibrium is reached so you get a higher maximum saturation of oxygen in the blood than in parallel flow so counter current flow is more efficient

Question 3

Where does gas exchange occur in bony fish

Answer 3

Gills

Question 4

What is the structure of gills in bony fish

Answer 4

Made up of thin plates called gill filaments, which are covered in structures called gill plates. The bottom edge of the gill filaments is called the gill arch which has gill rakers coming out of it

Question 5

Where are the gills located in bony fish

Answer 5

On the side of the fish head, behind the buccal cavity. With a flap on the skin called the operculum, and the opercula cavity behind the operculum before the gills

Question 6

How does the gas exchange surface maintain a large surface area for bony fish

Answer 6

Many gill filaments and plates which provide a large surface area

Question 7

How does the gas exchange surface maintain a short diffusion pathway for bony fish

Answer 7

Distance between outer layer of gill filaments and capillary walls is just one cell thick

Question 8

How does the gas exchange surface maintain a steep concentration gradient for bony fish

Answer 8

Due to counter current flow, there is always more oxygen in the water than in blood and so a steep concentration gradient is maintained