atrii

Atrii are the upper chambers of the heart, specifically the right atrium and the left atrium. The right atrium receives deoxygenated blood from the body through the superior and inferior vena cavae and then pumps it into the right ventricle. The left atrium receives oxygenated blood from the lungs via the pulmonary veins and pumps it into the left ventricle. The atria are separated from the ventricles by the atrioventricular valves, which include the mitral valve on the left side and the tricuspid valve on the right side. The atria play a crucial role in the heart's function by receiving blood and ensuring it is efficiently pumped into the ventricles for circulation throughout the body. The atria also contribute to the heart's electrical activity, helping to regulate the heart rate and rhythm.