OCR GCSE Biology Practice Exam 2026 – Comprehensive All-in-One Guide to Exam Success

The final stage of blood circulation within the heart involves the return of deoxygenated blood to the right side of the heart, specifically into the right atrium. This process is crucial as it allows the heart to continue its function as a pump, ensuring that blood is circulated effectively throughout the body.

After oxygen-rich blood, which has traveled through the aorta and supplied oxygen to body tissues, needs to return to the heart, it enters the right atrium through the superior and inferior vena cavae. This marks the beginning of the cycle for deoxygenated blood, as it prepares to be sent to the lungs for oxygenation. Understanding this cycle highlights the heart's role as a dual pump: one side dealing with oxygenated blood and the other managing deoxygenated blood.

In contrast to the other options, oxygenated blood entering the right atrium (first choice) would not make sense in this context, as that process does not occur. Oxygen delivery to the heart (third choice) refers to blood supply through the coronary arteries, which is part of the overall systemic circulation rather than the direct circulation process within the heart itself. Blood flowing to the pulmonary artery (fourth choice) occurs after deoxygenated blood has entered the right ventr