The Atria are two of the four chambers of the heart. The Atria are the upper chambers of the heart, and they are responsible for receiving blood from the body and pumping it to the ventricles. The other two chambers of the heart are the ventricles, which are the lower chambers that pump blood out of the heart to the rest of the body. Together, the four chambers of the heart work together to ensure that the body receives the oxygenated blood it needs to function properly.