LS2:Gas exchange

• 1.External gills
• 2.Internal gills
• 3.Lungs
• 4.Tracheae

active moving of the respiratory medium over the gas exchange

circulating blood over the gas exchange surfaces

• 1.Fish gills use
• -very effective mechanism for removing the maximum amount of oxygen from the water flowing over them
• - Countercurrent flow promotes diffusion of a substance (such as oxygen) down its concentration gradient from one fluid (water) to the other (blood)

site of gas excahnge and minimize the diffussion path between blood and water

bring blood to the gills

take blood away

air flows in and out by same path

the amount of air that moves in and out per breath

-at rest is meaured by a spirometer

the air that cannot be expelled from the lungs

the sites of human gas exchange

• 1.Hemoglobin composition
• 2. pH
• 3.2,3 BPG, lowers the affinity for O2