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Mediastinum

Contents

Overview

The mediastinum is an area found in the midline of the thorax 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. In this article, the borders of each section of the mediastinum and their contents will be discussed. Lastly, a pathological condition known as mediastinitis will be mentioned.

Recommended video: Mediastinum
Contents of the mediastinum seen from the lateral views.

Borders

Superior Mediastinum

The superior mediastinum begins at the level of the first rib and descends to the horizontal plane of the thoracic vertebra T4.

Superior mediastinum - ventral view

Superior mediastinum - ventral view

Anterior Inferior Mediastinum

The anterior inferior mediastinum starts from the thoracic vertebra T4 and continues to the diaphragm at the level of the thoracic vertebra T9. It extends posteriorly from the body of the sternum and transversus thoracis muscle to the fibrous pericardium.

Middle Inferior Mediastinum

The middle inferior mediastinum begins in the same area as the anterior inferior mediastinum and finishes also in the same area between the T9 and T10 vertebrae. It extends posteriorly between the width of the fibrous pericardium.

Posterior Inferior Mediastinum

The posterior inferior mediastinum again originates in the same place as the other two subdivisions but extends the deepest, to the vertebra T12. Sagittally, it runs from the posterior aspect of the fibrous pericardium to the vertebral column.

Mediastinum - lateral-left view

Mediastinum - lateral-left view

Contents

Superior Mediastinum

The superior mediastinum contains three visceral organs including the esophagus, the trachea and remnants of the thymus. The nerves that run through this area are three and there are also two different nervous plexuses. The phrenic nerve, the vagus nerve and the left recurrent laryngeal nerve are the singular nerves, while the cardiac plexus branches and the pulmonary plexus branches make up the peripheral neurological plexuses.

Left recurrent laryngeal nerve - ventral view

Left recurrent laryngeal nerve - ventral view

Arterial and venous constituents are comprised of:

Aortic arch - ventral view

Aortic arch - ventral view

Anterior Inferior Mediastinum

The anterior inferior mediastinum has no major contents save remnants of the thymus and some lymph nodes.

Middle Inferior Mediastinum

The middle inferior mediastinum contains a single nerve which is the phrenic nerve, the heart and the pericardium. The vessels present include:

Phrenic nerve - lateral-left view

Phrenic nerve - lateral-left view

Posterior Inferior Mediastinum

The posterior inferior mediastinum has possibly the most anatomical structures. It encompasses:

Azygos vein - lateral-right view

Azygos vein - lateral-right view

  • the hemiazygos veins
  • the accessory hemiazygos veins
  • the thoracic duct
  • the cisterna chyli
  • the vagus nerve
  • the esophageal plexus.
  • several branches of the sympathetic trunk, like the greater splanchnic nerve, the lesser splanchnic nerve and the least splanchnic nerve.

Greater splanchnic nerve - lateral-right view

Greater splanchnic nerve - lateral-right view

Mediastinitis

Mediastinitis is a term used to describe the inflammation of the tissue within the chest or the mediastinum. This disorder can be acute or chronic and is quite serious because the infection is in close proximity to so many essential organs and vessels. The most likely cause of this infection today is post surgical complications of cardiovascular or endoscopic surgery. This situation can become chronic, if a patient has an underlying disease such as tuberculosis or they are undergoing radiation therapy. Treatments depend on the patients case and can include therapy or even surgical decompression of the vessels.

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Show references

References:

  • Neil S. Norton, Ph.D. and Frank H. Netter, MD: Netter’s Head and Neck Anatomy for Dentistry, 2nd Edition, Elsevier Saunders, Chapter 22 Introduction to the Upper Limb, Back, Thorax and Abdomen, Page 584 to 585.
  • Michael Schuenke et al.: Atlas of Anatomy: Neck and Internal Organs, First Edition, Thieme, Thorax Chapter 1, 1.2 Divisions of the Thoracic Cavity and Mediastinum, 1.3 Overview of the Mediastinum and 1.4 Contents of the Mediastinum, Page 60 to 68.

Author:

  • Dr. Alexandra Sieroslawska

Illustrators:

  • Superior mediastinum - ventral view - Paul Kim
  • Mediastinum - lateral-left view - Yousun Koh
  • Left recurrent laryngeal nerve - ventral view - Yousun Koh
  • Aortic arch - ventral view - Yousun Koh
  • Phrenic nerve - lateral-left view - Yousun Koh
  • Azygos vein - lateral-right view - Yousun Koh
  • Greater splanchnic nerve - lateral-right view - 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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