Question

Describe the process of respiration in fish.

Answer 1

• Fish breathe using gills located on both sides of the head; gills are the respiratory organs that extract dissolved oxygen from water.
• Water is taken in through the mouth and forced over the gill surface; after passing the gills, it leaves through the gill slits (under the gill cover or operculum).
• Each gill has many gill filaments with thin, plate-like lamellae that provide a very large, thin-walled surface richly supplied with blood capillaries this maximises diffusion of O₂ into the blood and CO₂ out of it.
• Oxygen dissolved in the water diffuses across the thin gill epithelium into the blood; the blood carries oxygen to the tissues, while carbon dioxide produced by the tissues is transported back to the gills and expelled into the water.
• Because gills are specialised to extract dissolved oxygen from water and cannot work effectively in air, a fish taken out of water loses access to the oxygen its gills require and soon suffocates.