OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

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What occurs during the first stage of the circulatory system's process?

Oxygenated blood returns from the body
Deoxygenated blood is pumped to the lungs
Blood is delivered to body tissues
Oxygen is absorbed in the body

The correct answer is: Deoxygenated blood is pumped to the lungs

In the first stage of the circulatory system's process, deoxygenated blood is indeed pumped to the lungs. This occurs when the right side of the heart receives deoxygenated blood—those with low oxygen levels—coming from the body through the superior and inferior vena cavae. The heart's right atrium collects this blood and then pushes it into the right ventricle. When the right ventricle contracts, it sends the deoxygenated blood to the lungs via the pulmonary arteries. In the lungs, carbon dioxide is exchanged for oxygen through the process of gas exchange, which prepares the blood to return to the heart as oxygenated blood. This is essential for maintaining oxygen levels in the blood, which is necessary for the survival of body tissues. This process is a fundamental component of the circulatory system's role in sustaining life by ensuring that oxygen gets to cells and carbon dioxide is removed.