The left atrium is not always larger than the right. Either of the atrial appendages may be larger than the other. Both the left and right atria are located at the bottom of the heart and are separated from each other by the interatrial septum.
The atrial appendages are also separated from the ventricles by the cardiac skeleton. The left and right atrium each perform specific functions in the human heart. The blood from the body is returned to the right atrium via the vena cava, while the pulmonary veins bring blood from pulmonary circulation back into the left atrium.