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lies between the pericardium anteriorly and the vertebral column posteriorly and below the level of the plane that interesects the sternal angle and the T4-5 intervertebral disc. It contains the descending aorta, thoracic duct, esophagus, azygos veins, and vagus nerves.
the irregularly shaped lower part of the mediastinum parallel with the vertebral column. It is bounded ventrally by the pericardium, inferiorly by the diaphragm, dorsally by the vertebral column from the fourth to the twelfth thoracic vertebra, and laterally by the mediastinal pleurae. It contains the bifurcation of the trachea, two primary bronchi, the esophagus, the thoracic duct, many large lymph nodes, and various vessels, such as the thoracic part of the aortic arch. Compare anterior mediastinum, middle mediastinum, superior mediastinum.