The Heart
The heart itself is made up of 4 chambers, 2 atria and 2 ventricles. De-oxygenated blood returns to the right side of the heart via the venous circulation. It is pumped into the right ventricle and then to the lungs where carbon dioxide is released and oxygen is absorbed. The oxygenated blood then travels back to the left side of the heart into the left atria, then into the left ventricle from where it is pumped into the aorta and arterial circulation.