Parts of the heart are essential for the proper functioning of the cardiovascular system. Valves, which are six letters long, are structures that control the flow of blood in and out of the heart. The two main valves are the atria, which is five letters long, and the ARIA, which is four letters long. The atria are responsible for receiving oxygen-rich blood from the lungs and sending it to the ventricles, while the ARIA are responsible for sending oxygen-poor blood from the ventricles to the lungs. Together, these parts of the heart ensure that the body receives the oxygen it needs to function properly.