[Unit 6.3] | Gas Exchange In Fish

Question 1

Describe the structure of the gills.

Answer 1

• Vonsists of a gill bar

• With many projections called gill filaments which are stacked in a pile.

• Gill lamellae are discs that exist at right angles to the filaments & increase the surface area of the gill.

Question 2

What is a countercurrent flow?

Answer 2

• Where blood & water flow over the gill lamellae in opposite directions.

Question 3

Why is countercurrent flow more efficient than parallel flow?

Answer 3

• It allows for a diffusion gradient for the uptake of oxygen into the blood to be maintained across the entire width of the lamellae (allowing for around 80% oxygen uptake)

• With parallel flow, this gradient is only maintained along part of the length of the lamellae (allowing for only 50% oxygen uptake)