What structure lies posterior to the trachea in the superior mediastinum?

• A. Esophagus
• B. Aorta
• C. Thoracic duct
• D. Vagus nerve

Answer: (A)

In the superior mediastinum, the trachea sits in the midline as the airway, with the esophagus running directly posterior to it. This close, back-to-back arrangement means the esophagus is the structure immediately behind the trachea as both pass through the superior mediastinum and into the posterior mediastinum downward. The aorta is positioned more to the left and behind the trachea but not directly behind it; the thoracic duct travels posterior to the esophagus and toward the left, not right behind the trachea; and the vagus nerves lie more laterally on either side of the trachea rather than directly behind it.