Thoracic aorta

At a glance

English

Thoracic aorta

Latin (TA2)

Aorta thoracica

System

Artery

Region

Trunk

Side

Single, on the midline

About the thoracic aorta

The thoracic aorta, more fully called the descending thoracic aorta, is that segment of the aorta that lies in the chest below the arch. The aorta begins at the aortic valve as the ascending aorta, where the two coronary arteries leave its root, then curves backwards over the right pulmonary artery as the arch, which gives off the brachiocephalic trunk, the left common carotid and the left subclavian arteries. The thoracic aorta takes over at the level of the lower edge of the T4 vertebral body and runs down through the posterior mediastinum to the aortic hiatus of the diaphragm, opposite the twelfth thoracic vertebra, below which it is called the abdominal aorta.

It starts on the left side of the vertebral bodies and drifts towards the midline as it descends, so that by the time it reaches the diaphragm it lies squarely on the front of the spine. It often pushes the left pleura outwards so that it bulges into that side of the chest. Behind it lie the hemiazygos veins and the spine; on its right lie the azygos vein and the thoracic duct; on its left are the pleura and lung of that side. In front, from above down, it is related to the left lung root, then the pericardium over the left atrium, the oesophagus and the diaphragm.

The oesophagus and the oesophageal nerve plexus around it lie to the right of the aorta in the upper chest. Lower down the oesophagus crosses anterior to the aorta and then to its left as it approaches its own opening in the diaphragm, so the two tubes cross in a gentle spiral. This relationship is why an enlarged or diseased aorta can press on the oesophagus and cause difficulty swallowing.

Its branches are mostly small and fall into two groups. Visceral branches go to the bronchi and lungs, the oesophagus, the pericardium and the mediastinal lymph nodes and tissue. Parietal branches are the posterior intercostal arteries from the third space downwards, the subcostal arteries below the last rib and the superior phrenic arteries to the back of the diaphragm. Through these vessels it supplies the thoracic wall, much of the spinal cord and the organs of the posterior mediastinum.

Course and supply

Arises from

Continues from the aortic arch at the level of the lower edge of the T4 vertebra.

Ends in

Passes through the aortic hiatus of the diaphragm at the twelfth thoracic vertebra and continues as the abdominal aorta.

Supplies

Carries oxygenated blood to the body below the arch and, through its own branches, supplies the bronchi, oesophagus, pericardium, mediastinum, thoracic wall, upper abdominal wall and back of the diaphragm.