Venous heart is present in

The venous heart is a specific type of heart structure observed in some fish species. In organisms with a venous heart, only deoxygenated blood, carrying high levels of carbon dioxide (CO₂), flows through the heart. This unique adaptation allows the venous heart to efficiently pump blood to the gills, where oxygenation takes place.

Structurally, the venous heart is simpler compared to the four-chambered heart found in humans. It typically comprises two chambers: an atrium (sometimes referred to as an auricle) and a ventricle. These chambers are responsible for receiving blood from the veins and propelling it toward the respiratory organs for oxygen exchange. The venous heart lacks the complexity of separate pathways for oxygen-rich and oxygen-poor blood, which is a hallmark of more advanced circulatory systems in mammals.

The venous heart is a remarkable adaptation in aquatic environments, particularly in fish, where the efficient circulation of blood for oxygenation is critical for survival. Unlike terrestrial organisms with more complex cardiovascular systems, the venous heart is designed to meet the metabolic needs of species with simpler oxygen demands. This structural simplicity and functional specificity of the venous heart highlight its evolutionary significance in certain aquatic species.

In conclusion, the venous heart is an essential component of the circulatory system in certain fish species. By circulating deoxygenated blood through its two chambers, the venous heart facilitates the oxygenation process in the gills, supporting the survival and functionality of these aquatic organisms.