Which vertebral levels define the border where the arch of the aorta becomes continuous with the descending aorta?

Which vertebral levels define the border where the arch of the aorta becomes continuous with the descending aorta?

• A. T2/T3
• B. T4/T5
• C. T6/T7
• D. T8/T9

Answer: (B)

The border between the aortic arch and the descending thoracic aorta is at the level of the sternal angle (Angle of Louis), which corresponds to the intervertebral disc between the fourth and fifth thoracic vertebrae. In other words, the arch ends and the descending thoracic aorta begins around T4/T5. This landmark helps differentiate the arch (which gives its three branches) from the descending portion that runs down along the left side of the vertebral column. The other levels are above or below this transition point and thus do not mark where the arch becomes the descending aorta.

The border between the aortic arch and the descending thoracic aorta is at the level of the sternal angle (Angle of Louis), which corresponds to the intervertebral disc between the fourth and fifth thoracic vertebrae. In other words, the arch ends and the descending thoracic aorta begins around T4/T5. This landmark helps differentiate the arch (which gives its three branches) from the descending portion that runs down along the left side of the vertebral column. The other levels are above or below this transition point and thus do not mark where the arch becomes the descending aorta.