Mam can i get information about gill respiration with diagram??
Fish have a pair of gills, each of which is covered by a bony lid. A fish draws in water by closing the lid over its gills and opening its mouth. When the fish closes its mouth and opens the gill lid, the water is forced out and over the respiratory surfaces of the gill filaments.
Fish extract oxygen from the water and transfer it to their bloodstream using their gills which are richly supplied with blood vessels. Extracting oxygen from water requires a greater expenditure of energy than does extracting oxygen from air. The oxygenated water flows through the tiny gill filaments and it exchanges the carried oxygen for carbon dioxide through a process called diffusion. The folds of the filament are close enough together so that most of the water passing between them is involved in the gas-exchange process.
By using countercurrent circulation in the gill, the blood in the filament folds travels forward, in the opposite direction to the water flow, so that a constant imbalance is maintained between the lower amount of oxygen in the blood and the higher amount in the water, ensuring passage of oxygen to the blood.