How does the blood from the upper part of the body enter in right atrium?

Blood from the upper part of the body enters the right atrium through two major veins: the superior vena cava and the coronary sinus. The superior vena cava collects deoxygenated blood from the head, neck, arms, and upper torso, while the coronary sinus drains blood from the heart muscle itself. Once in the right atrium, this blood is then directed into the right ventricle, where it will be pumped to the lungs for oxygenation.