Fish Gaseous Exchange Sytem

Question 1

What is the detailed order of processes for water moving into the mouth of the fish to be used for gaseous exchange?

Answer 1

• Mouth is opened

• Floor of the buccal cavity (mouth) is lowered

• Volume of the buccal cavity increases

• Pressure in the buccal cavity decreases

• Water moves into the buccal cavity

• Opercular valve is shut

• Opercular cavity (containing the gills) expands

• Pressure in the Opercular cavity decreases

• Floor of the buccal cavity starts to move up

• Volume of the buccal cavity decreases

• Pressure in the buccal cavity increases

• Water moves from the buccal cavity over the gills

• Mouth closes

• Operculum opens

• Sides of the Opercular cavity move inwards

• Volume of the Opercular cavity decreases

• Pressure in the Opercular cavity increases

• Water is forced over the gills and out of the operculum

• Floor of the buccal cavity steadily moved up (maintaining flow of water over the gills)

Question 2

Where does the water go when fish use it for gaseous exchange?

Answer 2

Buccal cavity (mouth) -> over the gills -> out of the operculum

Question 3

What is the order of biological changes when water is used for gaseous exchange?

Answer 3

• Mouth opened

• Floor of buccal cavity lowered

• Opercular valve shut

• Opercular cavity (containing gills) expands

• Floor of buccal cavity moves up

• Mouth closes

• Operculum opens

• Sides of Opercular cavity move inwards

• Floor of buccal cavity steadily moved up

Question 4

How does a countercurrent exchange system allow for more efficient gas exchange than a parallel exchange system?

Answer 4

Blood and water flow in opposite directions, so an oxygen concentration gradient between the water and blood is maintained all along the gill. Oxygen continues to diffuse down the concentration gradient, so a much higher level of oxygen saturation of the blood is achieved.