3. The diagram shows a section of a human heart.
[VISUALIZATION: Diagram of the human heart in frontal section, showing the four chambers (right atrium, right ventricle, left atrium, left ventricle), major blood vessels (vena cava, pulmonary artery, pulmonary veins, aorta), and valves (tricuspid, pulmonary, mitral/bicuspid, aortic). Label the left ventricle as ‘X’.]
(a) Identify the structure labelled X. [1]
(b) Outline the function of the valves within the heart. [2]
(c) Explain **two** adaptations of structure X that relate to its function. [2]
(d) Describe the differences in blood composition between the pulmonary artery and the pulmonary vein. [2]
Question
Identify the structure labelled X. [1]
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Locate label ‘X’ on the diagram provided. Which chamber of the heart is it? Consider its position (left/right, upper/lower).
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Left ventricle
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Outline the function of the valves within the heart. [2]
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Think about the direction blood needs to flow through the heart chambers and major vessels. What structures ensure it doesn’t go the wrong way?
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Prevent backflow of blood and ensure unidirectional flow through the heart.
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Explain **two** adaptations of structure X that relate to its function. [2]
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Structure X is the left ventricle. Its main function is to pump blood to the entire body. What structural feature allows it to do this effectively? Link the structure to the pressure required.
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Adaptation: Thick muscular wall. Function link: Generates high pressure needed to pump blood to the entire body (systemic circulation).
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Describe the differences in blood composition between the pulmonary artery and the pulmonary vein. [2]
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Consider the pulmonary circuit: blood goes from the heart to the lungs via the pulmonary artery and returns via the pulmonary vein. What gas exchange occurs in the lungs?
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Pulmonary artery carries deoxygenated blood (lower O2, higher CO2). Pulmonary vein carries oxygenated blood (higher O2, lower CO2).
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