The heart through which venous CO2 rich blood is carried is called venous heart or venous heart. Blood with CO2 flows unidirectionally from the back to the front of the roe fish body. Sinus venosus enters from different parts of the body. Blood enters the atrium from the sinus venosus. Blood flows from the atrium. Then CO2 rich blood from the ventricles enters the bulbus arteriosus. In this way, the blood flows through the heart in a unidirectional manner through the veins. So roe fish heart is called venous heart or vein heart.
