Fish Respiratory System

In this post we are learning about the fish respiratory system.Gills are made to mediate the gas exchange in fish. The filaments are arranged in order  in rows in the gill arches, and each filament has lamellae, discs that contain capillaries. We know the blood enters and leaves the gills through these small blood vessels. Although gills are all restricted to a small section of the body, the immense respiratory surface created by the gill filaments provides the whole animal with an efficient gas exchange. The surrounding water keeps the gills wet.

A flap, the operculum, covers and protects the gills of bony fish. Water containing dissolved oxygen enters the fish's mouth, and the animal moves its jaws and operculum in such a way as to pump the incoming water through the gills. As water passes over the gill filaments, blood inside the capillaries picks up the dissolved oxygen. Since the blood in the capillaries flows in a direction opposite to the flow of water around the gill filaments, there is a good opportunity for absorption. The circulatory system then transports the oxygen to all body tissues and picks up carbon dioxide, which is removed from the body through the gills. After the water flows through the gills, it exits the body behind the fish's operculum.In the next post we learn about fish circulatory system and functions.