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descending aorta (anatomy)

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The descending thoracic aorta is the section of the vessel originating in continuity with the arch of the aorta at the level of inferior margin of the T4 vertebra on its left side. It terminates in continuity with the abdominal aorta at the aortic hiatus. It descends in the posterior mediastinum, initially to the left of vertebral bodies T4 to T6, then moving medially to run directly anterior to the inferior vertebral bodies. It gives off a number of branches during its course - see submenu.

The relations of the thoracic aorta as it descends are:

  • posterior:
    • and superiorly: left lateral side of vertebral bodies T4-6 and necks of ribs laterally; accessory hemiazygous veins; sympathetic trunk
    • and inferiorly: anterior surface of vertebral bodies; azygous vein
  • anterior, from superior to inferior:
    • left lung hilum
    • fibrous pericardium overlying left atrium
    • oesophagus passing anteriorly from the right side of the aorta
    • median arcuate ligament of aortic hiatus within the diaphragm
  • right:
    • and superior: thoracic duct; oesophagus
    • and inferior: thoracic duct; azygous tributaries; right mediastinal pleura
  • left: left mediastinal pleura and lung

Note that the oesophagus in relation to the aorta:

  • is initially on its right side
  • passes gently medially from the level of the tracheal bifurcation to lie on the anterior surface of the aorta
  • slightly to the right at the level of the oesophageal hiatus