How does a frog's heart differ from a human's heart?
Frog's heart is three chambered where there is no partition to separate oxygenated and deoxygenated bloods. Human heart is four chambered with completely separate double circulation.
Frog's heart has two accessory chambers, Sinus Venosus for receiving blood from body and Conus Arteriosus for sending the blood out from heart.
Human heart does not possess such chambers. Blood from body enters directly in right auricle and blood is pumped out by two ventricles.
Frog's heart has one ventricle, hence deoxygenated blood from body mixes with the oxygenated blood coming from lungs.