Where is it located and how does it run?
The thoracic aorta lies in the posterior mediastinum, resting directly on the vertebral column.
It is located at the level of the IV–XII thoracic vertebrae, along their bodies to the left of the midline. The upper segments are situated to the left of the spine; lower down, the aorta shifts somewhat to the right. At the level of the IV–VI thoracic vertebrae, it shifts posteriorly and to the left of the esophagus. At the level of Th12, the aorta passes through the aortic hiatus of the diaphragm and continues as the abdominal part (pars abdominalis aortae).
The vessel is enclosed in a fascial sheath connected to the adventitia of the aorta itself, as well as to surrounding structures: the mediastinal pleura, prevertebral fascia (fascia prevertebralis), and fibrous pericardium.
Topography and adjacent structures
The thoracic aorta has the following syntopy:
- Anteriorly: root of the left lung, left vagus nerve, left bronchus. Below the lung root, the esophagus crosses the aorta anteriorly from right to left.
- Posteriorly: hemiazygos vein and left intercostal veins. The thoracic duct lies adjacent to the posterior surface on the right.
- To the right: azygos vein (v. azygos).
- To the left: hemiazygos veins (vv. hemiazygos). The left outer circumference of the aorta is covered by the mediastinal pleura.
- Externally: branches of the sympathetic trunk (truncus sympathicus) and the plexuses formed by them lie adjacent to the fascial sheath of the aorta. Lymph nodes are located in the periaortic adipose tissue.
Relation to the esophagus
The position of the esophagus relative to the aorta changes at different levels:
- Upper third: the esophagus is located to the right of the aorta.
- Middle third: the esophagus is located anterior to the aorta.
- Lower third: the esophagus is located to the left of the aorta.
Below the lung root, the esophagus crosses the aorta anteriorly from right to left. At the level of the VII–X thoracic vertebrae, the esophagus and vagus nerves lie adjacent to the anteroposterior-right surface of the aorta, with the mediastinal pleura approaching from the right. Arteries branching from the thoracic aorta run along the walls of the esophagus and branch within them.
Branches of the thoracic aorta
The branches of the thoracic aorta are divided into two groups:
- Parietal (parietales).
- Visceral (viscerales).
Clinical significance
Endovascular surgery (Mapping)
To plan endovascular treatment, the aorta and iliac arteries are divided into zones. The descending thoracic aorta corresponds to zones 4 and 5. The border between them lies approximately at the level of the mid-descending thoracic aorta, near the T6 vertebra.
Thoracic aortic aneurysms
- Traumatic: occur due to mechanical damage to the vessel wall. Most commonly localized in the thoracic aorta during chest compression, such as in car accidents.
- Syphilitic: a complication of tertiary syphilis — syphilitic mesaortitis. Specific inflammatory infiltrate destroys the elastic fibers of the aortic tunica media, replacing them with fibrous tissue. Localization: thoracic aorta, ascending part, or arch. The shape can vary, most commonly saccular; size is 15–20 cm. Possible complications include erosion of the ribs and vertebral bodies, cardiac dysfunction, compression of the esophagus with dysphagia, compression of the recurrent nerve with persistent cough, airway compression with respiratory disorders, pain syndrome, and aneurysm rupture.
Diagnostics and decision-making factors
To detect inflammatory foci and assess large vessel damage, aortic CT angiography, MR angiography, and PET-CT of the aorta are used. Glucocorticosteroid treatment can suppress the inflammatory signal from vessel walls; 3–5 days after initiating GCS, imaging results may become false-negative. When determining indications for surgery, patient body size, aortic wall condition, and the ratio of ascending to descending aortic diameters are taken into account.
Class and exam questions
At what level does the thoracic aorta transition into the abdominal aorta?
The transition occurs at the level of the twelfth thoracic vertebra (Th12), where the aorta passes through the aortic hiatus of the diaphragm.
Which veins accompany the thoracic aorta?
To the right of the aorta runs the azygos vein (v. azygos), to the left — the hemiazygos veins (vv. hemiazygos); posteriorly lies the hemiazygos vein.
How is the esophagus positioned relative to the thoracic aorta?
In the upper third, the esophagus lies to the right of the aorta; in the middle, anteriorly; in the lower, to the left. Below the lung root, it crosses the aorta anteriorly from right to left.
What else to study on this topic
- Aortic arch
- Abdominal aorta
- Posterior mediastinum
- Topography of the esophagus
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