Gas exchange in fish

Question 1

Source of oxygen for fish?

Answer 1

Oxygen dissolved in water

Question 2

How does oxygen dissolved in water enter the fish in the first place?

Answer 2

Through the mouth

Question 3

What structure does water pass over in fish to acquire oxygen?

Answer 3

The gills

Question 4

What are gills made of?

Answer 4

Composed of gill filaments to increase the surface area
Then lamellae to increase surface area more

Question 5

Adaptations of gills for gas exchange

Answer 5

Large surface area due to lamellae
Steep concentration gradient of oxygen due to counter current system, ventilation system and circulation of fish
Thin surface layer of lamellae cells so short diffusion pathway

Question 6

Blood vessels in fish structure

Answer 6

Artery which contains deoxygenated blood taken to the gill to be oxygenated
Artery which has oxygenated blood taken away from gill to rest of body

Question 7

What system does the lamellae use to maintain a concentration gradient?

Answer 7

The counter current system

Question 8

Counter current structure description

Answer 8

Deoxy blood enters lamellae and leaves as oxy blood
Flows parallel to water with oxy dissolved in which becomes deoxy in opposite directions
So water with a higher oxy conc always flow next to blood with a lower oxy conc

Question 9

How does the counter current system help?

Answer 9

Maintains a steep concentration of oxygen OVER THE WHOLE LENGTH OF THE GILL

Question 10

How does ventilation and circulation of fish allow a steep concentration of oxygen?

Answer 10

Ventilation = water with high oxygen conc passed over the lamellae
Circulation = replaces oxygenated blood with deoxygenated with large capillary network in lamellae