Gas exchange in fish

Why do fish gulp water ?

When fish open their mouth, this create a larger volume in the oral comity

Large Volume = lower pressure in the oral cavity draws water in

What happen when the fish’s mouth close ?

There is a decrease in volume in the oral cavity = high pressure

Water forced out through operculum

What is the operculum ?

Most bony fish have a plate covering the gills

It’s closed when the mouth open, It’s open when mouth closed , volume decreases and pressure increases

This force the operculum open and after flow backwards over the gills

What are gills made from ?

It’s made of gill filaments and lamellar provide a massive surface area

Gill filaments are stacked in a pile, at the right angle at gill filaments are gill lamellae.

What is countercurrent exchange ?

Blood and water flow over the gill filaments and lamellae occurs in the opposite direction.

This main a concentration gradient across the entire width of the gill lamellae

Describe and explain the process of countercurrent process ?

1) Blood that has already been oxygenated meets the water, which holds max con.c of O2 so O2 diffuse from the water into the blood.

2) Blood that has little O2 meets water, which has had most oxygen removed. Diffusion of O2 from the water to blood.

3) Diffusion occurs over the entire width of the lamellae.

4) Approx 80 % of O2 availed in water is absorbed into the blood

key points in countercurrent exchange