3.1.1 Exchange surfaces – Bony fish ventilation and gas exchange Flashcards
(11 cards)
What is the gas exchange surface in a fish?
The gills (or more specifically the lamellae)
What is the function of the operculum?
It is a hard outer lining that protects the gills. It opens and closes to let water pass over the gills
What are the foldings of the gill filaments called?
Lamellae
Why are there many gill filaments and lamellae?
It gives a large surface area to maximise gas exchange.
Why does having a large number of blood capillaries increase gas exchange at the lamellae?
It maintains a diffusion gradient (the blood removes the oxygen and brings the carbon dioxide).
State 2 ways that a short diffusion pathway for the gases is achieved.
1) The lamellae wall is thin.
2) The blood capillaries flow very close to the lamellae surface.
How do fish get water (containing oxygen) to the gills?
- They gulp water (which contains oxygen) into the buccal cavity.
- The water flows over the gills where gas exchange can take place.
- The water leaves the fish through the operculum.
How does water get into the buccal cavity (mouth) of a fish?
- The buccal cavity opens.
- The operculum closes and the floor of the mouth is lowered.
- The volume of the buccal cavity increases so the pressure decreases.
- Water is drawn in due to the pressure differences
How does water get forced over the gills?
- The buccal cavity closes.
- The operculum opens and the floor of the mouth is raised.
- The volume decreases and the pressure in the buccal cavity increases.
- The water is pushed over the gills.
Describe the countercurrent multiplier at the gas exchange surface of a fish.
The water flows over the lamellae in an opposite direction to the blood.
How does the countercurrent multiplier increase the efficiency of gas exchange?
- It ensures that the concentration gradient is maintained across the whole lamella.
- So that diffusion can occur over the whole lamella.
