Ventilation in Fish & Insects

Question 1

How are Gill lamellae adapted for efficient gas exchange?

Answer 1

• Large SA for gas to diffuse over
• short diffusion distance through walls of lamellae into blood
• Large capillary network - maintains conc gradient for oxygen

Question 2

What is the countercurrent system?

Answer 2

• When blood flows through gill plate in one direction
• Water flows over gill plate in opposite direction

Question 3

Benefits of countercurrent system

Answer 3

• maintains large conc between water and blood
• conc of oxygen is always higher than in blood
• as much oxygen as possible diffuses into blood from water

Question 4

How are fish gills ventilated?

Answer 4

• Mouth open & buccal cavity floor opens
• buccal cavity volume increases, pressure decreases
• water is sucked in
• Mouth closes & buccal cavity floor is raised
• volume decreases, pressure increases
• water is forced out across gill filaments
• operculum open for water to leave gills