At what thoracic level does the ascending aorta join the aortic arch?

At what thoracic level does the ascending aorta join the aortic arch?

• A. T2/T3
• B. T6/T7
• C. T9/T10
• D. T4/T5

Answer: (D)

The switch from the ascending aorta to the aortic arch occurs at the level of the sternal angle (the angle of Louis), which corresponds anatomically to the T4/T5 vertebral level. The ascending aorta rises from the left ventricle in the middle mediastinum and, as it reaches the level where the manubrium meets the body of the sternum, it curves to form the aortic arch. That transition point is classically placed at T4/T5. The other levels are too high or too low for this junction.

The switch from the ascending aorta to the aortic arch occurs at the level of the sternal angle (the angle of Louis), which corresponds anatomically to the T4/T5 vertebral level. The ascending aorta rises from the left ventricle in the middle mediastinum and, as it reaches the level where the manubrium meets the body of the sternum, it curves to form the aortic arch. That transition point is classically placed at T4/T5. The other levels are too high or too low for this junction.