Module 3 - Ventilation in fish

Question 1

Describe the structure of gills and how they aid in gas exchange

Answer 1

• gills composed of thousands of filaments
• each filament is covered in lamallae
• lamallae are thin so the diffusion pathway of O2 from water into the blood is short and they increase SA
• large SA, good blood supply
• operculum protects

Question 1

What do fish need to maintain for efficient gas exchange?

Answer 1

• continuous flow of water over gills

Question 2

What is the mode of ventilation in fish called?

Answer 2

• gill irrigation

Question 3

Explain the process of ventilation in fish

Answer 3

• fish mouth opens, lowering the buccal cavity, allowing water to flow in as the volume of buccal cavity increases
• fish closes mouth, raising buccal cavity, reducing volume of it and increasing pressure, forcing water over the gills
• pressure builds up in gill cavity which forces the sides of operculum cavity to bulge out, increasing volume of the operculum cavity, decreasing the pressure, and drawing water over gills.
• operculum flaps open + contract, forcing water out
• process is repeated as fish opens its mouth

Question 4

What is counter-current flow in fish?

Answer 4

• water flows over gills in opposite direction blood flows in
• ensures that all the way across the gill filament, blood constantly meets water with higher O2 conc than it has, maintains diffusion gradient

Question 5

How does a countercurrent exchange system help fish with gas exchange?

Answer 5

• maintains steep concentration gradient