gas exchange in fish

why must fish have an efficient gas exchange system?

low O2 conc in water, need enough O2 for respiration

how are the gills adapted for efficient gas exchange?

• lamellae on gill filaments have a large SA

• good blood supply to maintain conc gradient

• thin, flattened cells so short diffusion distance

• permeable membrane allows gases to diffuse through tissues

what is the countercurrent exchange principle?

blood and water flow in opposite directions over the gills so blood always meets water with a high O2 conc, so a conc grad is maintained across the length of the gill

how does ventilation take place in fish?

fish opens mouth. volume increases, pressure decreases. water comes in. fish closes mouth so volume decreases and pressure increases. water forced over gills and out of operculum. gas exchange in gills