The descending aorta, a major continuation of the aortic arch, runs from the lower border of the T4 vertebra down to the T12 vertebra, transitioning from the thoracic to the abdominal aorta at the diaphragm. It sits in the posterior mediastinum, initially left of the vertebral column, moving medially to provide blood to the chest, esophagus, lungs, and diaphragm before branching into the abdominal aorta.
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Anatomical Structure and Location
- Segment: Extends from the end of the aortic arch (around T4) through the thoracic cavity to the diaphragm (T12 aortic hiatus).
- Path: Begins to the left of the thoracic vertebrae, eventually curving towards the midline as it descends.
- Relations: The esophagus is anterior to it, while the hemiazygos veins and vertebrae lie behind it.
Dimensions: Roughly 2 cm in diameter.
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Branches of the Thoracic Aorta
The thoracic portion of the descending aorta supplies surrounding structures through several branches:
- Bronchial arteries: Supply the bronchial tubes and lung tissue.
- Esophageal arteries: Supply the esophagus.
- Mediastinal branches: Supply lymph glands in the posterior mediastinum.
- Pericardial branches: Supply the posterior surface of the pericardium.
- Posterior intercostal arteries: Nine pairs that supply the intercostal spaces.
- Subcostal arteries: Located below the last ribs.
Superior phrenic arteries: Supply the superior surface of the diaphragm.
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Clinical Significance
- Aortic Coarctation: A narrowing often located near the ligamentum arteriosum.
- Aneurysm/Dissection: The descending aorta is a common site for aneurysms or aortic dissection.
Spinal Cord Supply: Radicular arteries, including the artery of Adamkiewicz, branch from intercostal arteries to supply the spinal cord; their damage during surgery can lead to paraplegia.
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The vessel is divided into three layers: the inner intima, the elastic media, and the outer adventitia. It ends by passing through the diaphragm to become the abdominal aorta