Deoxygenated blood returns from the body to the heart through the right atrium, which then contracts to transfer it to the right ventricle.

The left ventricle receives oxygenated blood from the left atrium and pumps it out to the body when it contracts, ensuring that vital organs receive oxygenated blood.

The left atrium receives oxygen-rich blood from the lungs and then relaxes to allow for the collection of this blood before it is transferred to the left ventricle.

The structure of gills includes thin, highly vascularized membranes with numerous folds and filaments, maximizing the surface area available for gas exchange. Additionally, the countercurrent flow of water and blood within the gills enhances the efficiency of oxygen uptake and ...

The surface area of the gills is crucial for efficient gas exchange in fishes because it allows for a larger area of contact between the water containing dissolved oxygen and the blood vessels within the gills, facilitating the uptake of ...