Fish Heart

Tuesday, April 24, 2012

The design of the heart varies widely from class to class. For example, the fish heart, unlike that of birds, mammals, and reptiles, has only two chamber instead of four: an atrium and a ventricle. The atrium receives venous blood from the sinus venosus, which is a small sac or pouch that collects the carbon-dioxide-rich blood from the body tissues, and sends it to the ventricle, which pumps this blood to capillaries in the gills where it is oxygenated. From the gills it goes straight to capillaries in the body tissues and back to the heart.