Answer to The Overeating Society

Correct answer is E. The question is asking at what level does the trachea bifurcate. Tracheal bifurcation is associated with the sternal angle, or the Angle of Louis (as labeled in the clinics), which occurs at the level of the second rib. In the image, the only other structure visible that is also associated with the sternal angle is the ascending aorta. The arch of the aorta, labeled 4, is above the sternal angle. At level 3, the trachea and major branches of the aorta are just posterior to the suprasternal notch; hence, this is considered the boundary between the neck and the thorax. Levels 1 and 2 are in the neck.

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Answer to this question is based on material presented in lectures 13 of the Thorax Lecture Series.