left subclavian artery

abeled CT: 

labeled CT: 

What is outlined in yellow on the labeled CT images? Be specific!

Explanation

The labeled CT images show the course of the ascending aorta, aortic arch, and descending aorta, along with the three major branches that arise from the aortic arch.  The branch outlined in yellow is the left subclavian artery.

The aorta is outlined in red, the left common carotid artery in purple, and the left subclavian artery in yellow. The only branches that arise from the ascending aorta are the coronary arteries.  The descending aorta gives off the bronchial arteries, the esophageal arteries, mediastinal arteries and the posterior intercostal arteries.  After the thoracic aorta enters the abdomen via the aortic hiatus of the diaphragm, it becomes the abdominal aorta.  Two of the midline branches of the upper abdominal aorta are also labeled:  the celiac artery (in green) and the superior mesenteric (in dark blue).

Image A shows an anomaly of the aortic branches:

Image B shows labels on the structures in these CT images.

The aorta is outlined in red.  The right subclavian artery has an anomalous origin, coming off as the last branch of the aortic arch and passing posterior to the trachea and esophagus.  This is called an aberrant right subclavian artery.  The aberrant vessel is shown in pink.  The right common carotid artery (there is no brachiocephalic artery in this case, since the right common carotid artery and right subclavian artery do not arise from a common trunnk) is shown in blue, the left common carotid artery in yellow and the left subclavian artery in green.