The gills of fresh fish are filamentous. The gills of fresh fish have a red filamentous structure. Red is because capillaries are distributed all over the fish, which is beneficial to oxygen exchange. Filamentous structure increases the contact area with oxygen, so gills are the respiratory organs of fish.

The respiratory organ of fish is gill, which is characterized by that each gill consists of many gill filaments, which are rich in capillaries and can fully exchange gas in water.

Fish gill details

There are two large gill covers, and the cavity in the gill cover is called gill cavity. Open the gill cover, you can see that there are four gills on both sides of the throat, and each gill is divided into two rows. Each row of gills consists of many gill filaments, and there are many small gill pieces on both sides of each gill filament.

When in the water, all gills, gills and gills are completely opened, which increases the contact area between gills and water and increases the chance of absorbing dissolved oxygen in the water. There are capillaries in the gill flap, and the epidermis here is very thin. When the blood flows through here, the gas exchange is completed, and the carbon dioxide brought with it is sent to the water through the thin wall of the gill flap.

At the same time, it absorbs oxygen in water, which is transported to all parts of the body with blood circulation. Because the mouth and gill cover are alternately opened and closed, water can continuously enter the mouth from the mouth, reach the gill cavity through the pharynx, contact with the gill filaments, and then be discharged from the body through the gill holes, and the fish's breathing function is completed in this process.