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

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Prepare for the OCR GCSE Biology Exam with detailed quizzes, flashcards, and explanations. Enhance your understanding of biology concepts and get exam-ready today!

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During which stage does oxygenated blood return from the lungs to the heart?

First stage
Second stage
Third stage
Fourth stage

The correct answer is: Second stage

Oxygenated blood returns from the lungs to the heart during the second stage of the circulatory process, known as pulmonary circulation. In this stage, blood that has been oxygenated in the lungs travels back to the left atrium of the heart through the pulmonary veins. This process is crucial because it allows the heart to receive oxygen-rich blood that will be pumped to the rest of the body. Understanding this stage is important when studying the overall functioning of the cardiovascular system, highlighting the role of the lungs in oxygenation and the heart's role in distributing that oxygen to tissues.