The atria are the two upper chambers of the heart, specifically the right atrium and the left atrium. They play a crucial role in the heart's function by receiving blood returning from the body and lungs. The right atrium collects deoxygenated blood from the body through the superior and inferior vena cavae, while the left atrium receives oxygenated blood from the lungs via the pulmonary veins. Once the atria fill with blood, they contract to push it into the lower chambers of the heart, known as the ventricles. The right ventricle then pumps the deoxygenated blood to the lungs for oxygenation, while the left ventricle sends oxygen-rich blood to the rest of the body. This coordinated