Stock Photo - THORAX, DRAWING The posterior mediastinum, anterior view ablation of the heart, lungs and pleurae. The mediastinum is the anatomical region of the thorax located between the two lungs. The mediastinum contains notably : _ the esophagus, _ the thoracic aorta, _ the azygos venous system draining the blood of certain structures of the thorax and the abdomen in blue, _ the thoracic duct, collecting the lymph coming from the left part of the body in green, _ the sympathetic trunk of the sympathetic nervous system, with the ganglion cells in yellow, _ the right and left vagus nerves in yellow. The azygos venous system is constituted of the azygos vein on the right and superior hemiazygos veins accessory and inferior hemiazgos veins on the left, dashed line which anastomose themselves. It drains the blood coming from the following veins : intercostal, lombar, mediastinal, esophageal, pericardial and bronchial . The hemiazygos veins throw into the azygos vein which pours itself the blood in the vena cava superior.