mediastinum

• Mediastinum


  The central compartment of the thoracic cavity in between both lungs that contains a group of structures within the thorax
• Mediastinum boundaries

  • Superior boundary: Thoracic inlet
  • Inferior boundary: Diaphragm
  • Anterior boundary: Sternum
  • Posterior boundary: Vertebral column
  • Lateral boundary: Pleura
• Subdivisions of the mediastinum

  1. Divided into superior and inferior parts by an imaginary horizontal plane passing through the manubriosternal joint and the disc between fourth and fifth thoracic vertebrae

  2. Inferior mediastinum is further subdivided into anterior, middle and posterior parts
• Superior mediastinum


  • Anterior boundary: Manubrium sterni
  • Posterior boundary: Upper 4 thoracic vertebrae
  • Superior boundary: Thoracic inlet
  • Inferior boundary: Imaginary line between sternal angle and disc between T4 and T5
  • Lateral boundary: Pleura
• Contents of superior mediastinum

  • Arteries: Arch of aorta and its branches
  • Veins: Right brachiocephalic vein, Left brachiocephalic vein, Upper 1/2 of SVC, Termination of azygos vein
  • Tubes: Trachea, Esophagus, Thoracic duct
  • Nerves: Phrenic nerves, Vagus nerves, Left recurrent laryngeal nerve, Superficial cardiac plexus
  • Muscles: Sternohyoid and sternothyroid
  • Remains of thymus
• Anterior mediastinum


  • Anterior boundary: Body of sternum
  • Posterior boundary: Pericardium
  • Superior boundary: Imaginary line between sternal angle and disc between T4 and T5
  • Inferior boundary: Diaphragm
  • Lateral boundary: Pleura
• Contents of anterior mediastinum

  • Superior and inferior sternopericardial ligaments
  • Remains of thymus
  • Internal thoracic artery
  • Lymph nodes (parasternal)
• Middle mediastinum


  • Contents: Heart and pericardium, Arteries: Ascending aorta and pulmonary trunk, Veins: Lower 1/2 of SVC, Termination of IVC, Termination of 4 pulmonary veins, Nerves: Phrenic nerves, Deep cardiac plexus, Tubes: Tracheal bifurcation and bronchi
• Posterior mediastinum


  • Anterior boundary: Pericardium
  • Posterior boundary: Lower 8 thoracic vertebrae
  • Superior boundary: Imaginary line between sternal angle and disc between T4 and T5
  • Inferior boundary: Diaphragm
  • Lateral boundary: Pleura
• Contents of posterior mediastinum

  • Descending thoracic aorta
  • Esophagus
  • Thoracic duct
  • Azygos and the two hemiazygos veins
  • Vagus and splanchnic nerves
  • Posterior mediastinal lymph nodes