Amphibian Circulatory System

A typical circulatory system of the class Amphibia.  Note the three chambered heart (most visible in 4) where oxygenated blood (from capillaries in gills, lungs and/or skin) and de-oxygenated blood from systemic tissues mix in the ventricle before returning to both sets of tissues via a fork in the aorta.  The heart is shown in two views looking both at the ventral (2) and dorsal (3) surfaces.