What is the primary function of the upper right chamber of the heart?

The primary function of the upper right chamber of the heart, known as the right atrium, is to collect blood that has returned to the heart from the body through the superior and inferior vena cavae. This blood is deoxygenated, meaning it has already delivered its oxygen to the tissues and is returning to the heart to be reoxygenated. Once the right atrium collects this blood, it then passes it into the right ventricle, which pumps it to the lungs for oxygenation.

In this context, the other options describe functions of different parts of the heart. The right ventricle is responsible for pumping blood to the lungs, while the left atrium receives oxygen-rich blood from the lungs, and the left ventricle pumps oxygenated blood to the rest of the body. Therefore, the function of collecting blood from the body is uniquely associated with the right atrium, making it the correct answer.