Mediastinum

Superior mediastinum

The superior mediastinum is a space bounded anteriorly by the manubrium of the sternum, and posteriorly by the bodies of T1-T4 vertebrae. Its superior border is an oblique plane extending from the jugular notch of the manubrium to the superior border of T1 vertebra. Whilst the inferior border is a transverse plane extending from the sternal angle to the T4-T5 intervertebral disc.

Want to make sure you're learning the anatomy of the mediastinum as efficiently as possible? Discover the importance of the active recall learning method.  

The transverse plane separates the superior from the inferior mediastinum. Lastly, the lateral borders are the mediastinal surfaces of parietal pleura on each side.

The contents of the superior mediastinum includes many organs, vessels and nerves;

• Thymus
• Trachea
• Esophagus
• Aortic arch
• Brachiocephalic trunk
• Left common carotid artery
• Left subclavian artery
• Internal thoracic arteries
• Superior vena cava
• Left superior intercostal vein
• Brachiocephalic veins
• Phrenic nerves
• Vagus nerves
• Left recurrent laryngeal branch of the left vagus nerve
• Thoracic duct
• Lymph nodes and vessels, 
• Other small arteries, veins and nerves

We’ve got you covered with the anatomy of the structures found within the superior mediastinum.

Inferior mediastinum

The inferior mediastinum extends from the inferior border of the superior mediastinum to the diaphragm. It is subdivided anterior-to-posterior into three spaces: 

• Anterior mediastinum - posterior to the body of the sternum and anterior to the pericardium
• Middle mediastinum - bounded by the pericardium, which encloses the heart and origins of the great vessels
• Posterior mediastinum - posterior to the pericardium and anterior to the vertebrae

Solidify your knowledge with our quiz:

New classification of mediastinal compartments

Recently, a group of specialists in thoracic surgery, diagnostic imaging, oncology and pathology developed a new classification for the mediastinal compartments.

This new classification is based on cross sectional images, and divides the mediastinum into three compartments (prevascular, visceral and paravertebral), all of which are bordered superiorly by the thoracic inlet and inferiorly by the diaphragm and limited laterally by the parietal mediastinal pleura.

The prevascular compartment  is limited anteriorly and posteriorly by the posterior surface of the sternum and the anterior aspect of the pericardium, respectively. Its name is derived from the fact that this compartment lies anterior to the major vessels of the mediastinum (ascending aorta and its branches, superior vena cava and pulmonary vessels). Its primary contents are the thymus, and the left brachiocephalic vein.

Lying posterior to the prevascular compartment is the visceral compartment which is limited posteriorly by a vertical line that connects a point on each thoracic vertebral body, 1 cm posterior to its anterior border. It contains the trachea, esophagus, heart, the ascending and descending aorta, along with the aortic arch and its branches, the superior vena cava, the pulmonary arteries and the thoracic duct.

The posteriormost division is the paravertebral compartment whose posterolateral borders are formed by a vertical line against the posterior border of the chest wall at the lateral margin of the thoracic spine. Its main contents are the thoracic spine, paravertebral soft tissues, sympathetic trunk and azygos/hemiazygos venous system.

This classification consolidates multiple different classifications used by different medical specialties, facilitating the communication between them.