What great vessel connects to the right atrium and drains blood from the upper right extremities, neck and head?

The great vessel that connects to the right atrium and drains blood from the upper right extremities, neck, and head is the Superior Vena Cava. This large vein plays a crucial role in the circulatory system by transporting deoxygenated blood from the upper body back to the heart.

The Superior Vena Cava specifically receives blood from structures located above the diaphragm, such as the arms and head, and directs it into the right atrium, where it can then be sent to the right ventricle and eventually to the lungs for oxygenation. This is essential for maintaining proper blood circulation and ensuring that deoxygenated blood is efficiently returned to the heart for reoxygenation.

In contrast, the Inferior Vena Cava drains blood from the lower body, including the lower extremities and abdomen, while the Right and Left Pulmonary Veins transport oxygenated blood from the lungs back to the left atrium of the heart. Therefore, the function of the Superior Vena Cava is specific to the upper portion of the body's venous return system, making it the correct answer to the question.