text: The<unk>  is contained in the posterior mediastinal cavity.
  It begins at the lower border of the fourth<unk>  vertebra where it is continuous with the<unk> c arch, and ends in front of the lower border of the twelfth<unk>  vertebra, at the<unk> c hiatus in the diaphragm where it becomes the abdominal<unk> .
  At its commencement, it is situated on the left of the vertebral column; it approaches the median line as it descends; and, at its termination, lies directly in front of the column.
  The vessel describes a curve which is concave forward; as the branches given off from it are small, its diminution in size is insignificant.
option_0: Thoracic aorta
option_1: Ascending aorta
option_2: Descending aorta
option_3: Coronary sinus
option_4: Aortic sinus
option_5: Subclavian vein
option_6: Inferior vena cava
option_7: Superior vena cava