It is in relation, in front, with the vagus nerve, the cardiac nerves, and the phrenic nerves, which lie parallel with it, the left common carotid artery, left internal jugular and vertebral veins, and the commencement of the left innominate vein. It is covered by the sternothyroid muscle, the sternohyoid muscle, and the sternocleidomastoid muscle. Behind, it is in relation with the esophagus, thoracic duct, left recurrent laryngeal nerve, inferior cervical ganglion of the sympathetic trunk, and the longus colli muscle; higher up, however, the esophagus and thoracic duct lie to its right side; the latter ultimately arching over the vessel to join the angle of union between the subclavian and internal jugular veins. Medial to it are the esophagus, trachea, thoracic duct, and left recurrent laryngeal nerve. Lateral to it are the left pleura and lung.