Gas exchange in a fish

Question 1

How does oxygen dissolve in water

Answer 1

Oxygen dissolves less readily in water and contains 30 times less oxygen than air

Question 2

What is the structure of a fish gas exchange system

Answer 2

• All components are thin so a short diffusion pathway is created
• Series of gills on each side of the head
• Each gill arch has 2 stacks of filaments (give a large surface area so increase rate of diffusion)
• Filaments have rows of lamellae on their surface

Question 3

What are lamellae and what do they do

Answer 3

single layer of flattened cells covered by capillary’s

increase the surface area even more

Question 4

What are the mechanisms of the gas exchange in fish

Answer 4

• Capillary’s in lamellae ensure the blood flows in the opposite direction to water flow (counter-current system)
• Counter-current system maintains concentration gradient across the capillary’s
• Water with the lowest oxygen concentration is adjacent to most oxygenated blood

Question 5

What is the counter-current system in a fish

Answer 5

Blood flows through the capillary’s in the lamellae in one direction and the water flows in the other direction. This means the water with the least oxygen concentration meets the blood with the least concentrated water. (Water concentration is always slightly higher)

Keeps a steep concentration gradient which is maintained over the whole length of the gill so as much oxygen can diffuse from the water into the blood

google picture of it

Question 6

What are the advantages of the Counter current system

Answer 6

• Maintains a concentration gradient
  (facilitating continuous diffusion into blood as blood and water flow opposite ways)
• Maximises oxygen uptake (fish can extract up to 80-90% of oxygen passing over gills
• Efficient gas exchange so more respiration takes place so more ATP is released meaning the fish can swim faster etc

Question 7

why can fish with more lamellae swim faster

Answer 7

Having more lamellae increases the SA meaning there’s a higher diffusion of oxygen into the blood which can then be used for respiration where more ATP is released so there’s more energy meaning the fish can swim faster