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Mediastinum: want to learn more about it?

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Mediastinum

The mediastinum is an area found in the midline of the thoracic cavity, that is surrounded by the left and right pleural sacs. It is divided into the superior and inferior mediastinum, of which the latter is larger.

The inferior mediastinum is further divided into the anterior, middle and posterior mediastinum. Every compartment of the mediastinum contains many vital organs, vascular and neural structures that are closely related one to another.

Such a rich content of the mediastinum indicates its significance from the aspect of the anatomy.

Key facts
Superior mediastinum Borders: first rib (superior) - T4 (inferior)
Content: esophagus, trachea, thymus; phrenic nerve, vagus nerve, left recurrent laryngeal nerve; superior vena cava, brachiocephalic veins, aortic arch, thoracic duct
Anterior inferior mediastinum Borders: T4 (superior) - T9 (inferior);  sternum (anterior) - pericardium (posterior)
Content: remnants of the thymus, lymph nodes
Middle inferior mediastinum Borders: T4 (superior) - T9 (inferior); anterior aspect of pericardium (anterior) - posterior aspect of pericardium 
Content: phrenic nerve, heart, pericardium, ascending aorta, pulmonary trunk, superior vena cava, pericardiacophrenic artery
Posterior inferior mediastinum Borders: T4 (superior) - T12 (inferior); posterior aspect of pericardium (anterior) - spine (posterior)
Content: esophagus, thoracic aorta, azygos veins, hemiazygos veins, accessory hemiazygos veins, thoracic duct, cisterna chyli, vagus nerve, esophageal plexus, greater, lesser and least splanchnic nerves
Clinical relations Mediastinitis (inflammation of the structures within the mediastinum)

Thoracic cavity

This cylindrical cavity of the chest is enclosed by the thoracic walls and the diaphragm. Superiorly it communicates with the neck, through the superior thoracic aperture.

The thoracic cavity houses three compartments: left and right pleural cavities and the mediastinum. The pleural cavities are placed in the lateral parts of the thorax, they contain the lungs and their associated structures. The mediastinum sits centrally, between the pleural cavities. 

Mediastinum

The mediastinum, or mediastinal cavity, is a visceral compartment of the thoracic cavity. It completely separates the two pleural cavities by being placed longitudinally between them in a median sagittal position. It extends superoinferiorly from the superior thoracic aperture to the diaphragm, anteroposteriorly from the sternum to the bodies of thoracic vertebrae, and laterally from the mediastinal pleura of the adjacent pleural cavities. The main mediastinal contents are the heart, esophagus, trachea, thoracic nerves and systemic blood vessels. 

Lateral views of mediastinum (diagram)

The mediastinum is divided into the superior mediastinum and inferior mediastinum by a transverse plane that extends from the sternal angle (manubriosternal junction), to the intervertebral disc between T4 and T5 vertebrae.

For more information about the mediastinal contents we encourage you to reinforce your knowledge with our video tutorial and quiz.

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.

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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
  • Left superior intercostal vein 
  • 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. Whether you prefer to read, watch a video, or quiz yourself!

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
Contents of the inferior mediastinum
Anterior mediastinum Inferior portion of thymus
Fat
Connective tissue
Lymph nodes
Mediastinal branches of internal thoracic vessels
Sternopericardial ligaments
Middle mediastinum Pericardial sac
Heart
Origins of great vessels: pulmonary trunk, ascending aorta, pulmonary veins, superior vena cava, inferior vena cava
Tracheal bifurcation and main bronchi
Posterior mediastinum Esophagus and esophageal plexus
Thoracic aorta and its branches
Azygos and hemiazygos venous systems
Thoracic duct
Sympathetic trunk
Thoracic splanchnic nerves

Learn everything about the inferior mediastinum contents in a more fun and engaging way with our articles, quizzes and video tutorials.

Lymphatics of the mediastinum

There are several groups of lymph nodes scattered within mediastinum. Most of the mediastinal organs drain into the thoracic duct. The interesting exception is the right side of the heart, which together with the right lung, right sides of head, neck and thorax, drains into the right lymphatic trunk. Learn everything about mediastinal lymphatics with this article, video tutorial and quiz.

Solidify your knowledge about the mediastinum anatomy by taking this specially designed quiz, in which you will find out more about the mediastinum anatomy and contents!

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Mediastinum: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 1,165,835 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

Authors and review:

  • Jana Vaskovic
  • Nicola McLaren

Illustrators:

  • Mediastinum (left lateral view) - Yousun Koh
  • Lateral views of mediastinum – Yousun Koh
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

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