Atrium

atrium (plural, atria). An upper chamber that receives blood from the veins returning to the verte­brate heart .And then pushes the blood to the ventricles, the lower chambers. There is a left and right atria. Oxygenated blood returns from the lungs into the left atria and gets pushed down to the left ventricle. The left ventricle pumps the blood out to the rest of the body, transporting the oxygen to parts of the body that need it. Blood returning from its voyage through the body arrives in the right atrium. It then goes into the right ventricle. From which it goes through the lungs again to get more oxygen. And the cycle continuously repeats itself.