Fig. 1.1 Fig. 1.1 shows a vertical section through a mammalian heart, viewed from the front. The chambers and major blood vessels are labelled with the lett...
Question 1 Report
Fig. 1.1
Fig. 1.1 shows a vertical section through a mammalian heart, viewed from the front. The chambers and major blood vessels are labelled with the letters A to F. The heart is a double pump that keeps oxygenated and deoxygenated blood separate as they flow through it during one heartbeat.
(a) State the letter, A to F, that labels the chamber with the thickest muscular wall. [1]
(b) Name the blood vessel that carries oxygenated blood from the lungs back to the heart. [1]
(c) Describe the path taken by a red blood cell from the moment it enters the heart in the vena cava until it leaves the heart in the pulmonary artery. [4]
(d) Explain how the structure of the left ventricle wall is related to its function. [3]
(e) Explain the importance of the valves found between the atria and the ventricles. [3]
(f) Suggest one effect on the body if the septum between the two ventricles has a small hole. [2]
Answer Details
This question tests heart structure and the pathway of blood through it. The heart is a double pump: the right side handles deoxygenated blood to the lungs, the left side handles oxygenated blood to the body.
(a) The chamber with the thickest muscular wall is the left ventricle [1], because it pumps blood the greatest distance.
(b) The vessel carrying oxygenated blood from the lungs to the heart is the pulmonary vein [1]. Note that veins usually carry deoxygenated blood, but the pulmonary vein is the exception.
(c) A red blood cell follows this route, one mark for each structure in the correct order: vena cava, then right atrium, then through the tricuspid (right atrioventricular) valve, then right ventricle, then pulmonary artery [4].
(d) The left ventricle wall matches its function because it has a thick muscular wall [1] that contracts with great force, producing high pressure [1] to pump blood all around the body over a long distance [1]. More muscle means more force.
(e) The atrioventricular valves are important because they prevent backflow of blood [1] from the ventricles back into the atria [1] when the ventricles contract, keeping blood flowing in one direction [1].
(f) A hole in the septum would let oxygenated and deoxygenated blood mix [1], so less oxygen is delivered to the body tissues, causing tiredness or breathlessness [1]. The septum's job is to keep the two blood types separate.
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