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Chapter 78: Electrophysiologic Anatomy

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Which of the following is false regarding the the heart borders and surrounding structures?

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A. The right border of the heart is formed exclusively by the right atrium

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B. The inferior border is marked by the right ventricle

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C. The left border is formed by the aortic arch, the pulmonary veins, and the left ventricle

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D. The left atrium forms most of the posterior border

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E. The pulmonary trunk crosses over the root of the aorta anteriorly such that the aorta ascends behind

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The answer is C. (Hurst’s The Heart, 14th Edition, Chap. 78) The sloping left border is often described as having three to four “moguls” on the chest x-ray, which correspond to the aortic arch, pulmonary artery (not pulmonary veins), and left ventricle (superior to inferior). Occasionally, the left atrial appendage is visible between the pulmonary artery and the left ventricle. The aortic knob appears above the pulmonary trunk. The right border of the heart is formed exclusively by the right atrium (option A), with the superior and inferior caval veins joining at its upper and lower margins. The inferior border lying horizontally on the diaphragm is marked by the right ventricle (option B). The left atrium is the most posterior cardiac chamber (closest to the spine), and the esophagus is immediately behind the left atrium (option D). In the hilum, the aortic knob is superior and rightward and the main pulmonary artery (or pulmonary trunk) is inferior and leftward (option E). The pulmonary trunk crosses over the root of the aorta anteriorly such that the aorta ascends behind or posterior to it.

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Regarding the right atrium, which of the following is true?

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A. The right atrium is rightward and anterior when compared to the left atrium, which is leftward and posterior

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B. The right atrium is more superior (cephalad) than the left atrium

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C. During embryonic development, the eustachian valve separates the sinus venosus from the heart

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D. The sinus node is a subepicardial structure that is found at the posteroseptal aspect of the superior vena cava–right atrial junction

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E. The tendon of Todaro guards the orifice of the coronary sinus

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The answer is A. (Hurst’s The Heart, 14th Edition, Chap. 78) The right atrium is rightward and anterior, whereas the left atrium is leftward and posterior. The left atrium is also more superior (cephalad) than the right atrium (option B). During embryonic development, ...

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