The primary function of the heart is to pump oxygen rich blood to organs such as the brain, liver, and kidneys as well as all other tissue. The heart of the frog is different from the hearts of warm-blood animals such as humans. Although mammals have four chambers, amphibians, which are cold-blood animals, have only three consisting of two upper compartments referred to as the atria and only one lower vault known as the ventricle. As the atria contract, blood is sent into the single ventricle. A swelling located near the outflow portion of the ventricle, referred to as bulbus cordus, leads the blood into a series of aortic arches to be transported into the major arteries and distributed throughout the body.