The mediastinum is the region between the pulmonary cavities. It is covered by the mediastinal pleura and extends from the thoracic inlet superiorly to the diaphragm inferiorly.

Mediastinal regions

Region Contents
Superior mediastinum • Superior vena cava
• Brachiocephalic veins
• Arch of aorta
• Thoracic duct
• Trachea
• Oesophagus
• Thymus
• Vagus nerve
• Left recurrent laryngeal nerve
• Phrenic nerve
Anterior mediastinum • Thymic remnants
• Lymph nodes
• Fat
Middle mediastinum • Pericardium
• Heart
• Aortic root
• Arch of azygos vein
• Main bronchi
Posterior mediastinum • Oesophagus
• Thoracic aorta
• Azygos vein
• Thoracic duct
• Vagus nerve
• Sympathetic nerve trunks
• Splanchnic nerves

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The commonest causes of an anterior mediastinum mass can be remembered by the 4 T's: teratoma, terrible lymphadenopathy, thymic mass and thyroid mass

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