Bob hambelton, age 11, of eugenej, ore , for his question:
How do the gills of a fish work?
We need a steady supply of the element oxygen and s0 d0 the fishes that 11ve in the sea. We take gaseous oxygen from the air, but the fishes cannot do this. They take oxygen that is dissolved in the water, and they do their breathing with gills in much the same way as we breathe with our lungs.
The gills of a fish are on the sides of his head, dust about where we would Expect his ears to be. In fact, you might mistake his round gill covers for a pair of Ears. These sturdy flaps protect the working tissue of the gills. Water is constantly flowing from the gills through the round slits of the gill covers, and water is constantly flowing into the gills through a series of slits in the fish's mouth.
A fish is forever opening and closing his mouth, but he is not swallowing all that water. After each gulp, he closes the muscles in his throat and forces the Water through the slits inside his mouth. These slits may be fitted with strainers to Sift out food and other lumpy material. The water goes from the mouth into the gills which rest in bony pockets, one on each side of the fish's head. The gills are thin layers of tissue covered with the finest skin or membrane and Stuffed with the smallest blood vessels. The gills are divided into fine fragments so that the streaming water can wash over as much surface as possible. The water is separated from the gill blood vessels by thin thin walls of membrane.
The water contains a supply of dissolved oxygen. Molecules of oxygen in the water pass right through the membrane walls to land red cells in the fish's blood stream. Molecules of waste carbon dioxide pass through the membrane walls and loin the water streaming away through the fish's gill slits.
The fish has a beating heart that pumps blood to all the living cells of his body, and his blood stream carries a constant supply of lift giving oxygen from his gills. It also gathers up waste carbon dioxide from the cells and totes it back to the gills where it is sent out into the sea.
Water, of course, is a compound of the elements hydrogen and oxygen. But fishes cannot take the oxygen from molecules of water. Some of their vital oxygen comes from the air and is mixed with the water by romping waves and plunging waterfalls. Some comes from plants as they pour oxygen into the water in the process of photosynthesis.