Posterior mediastinum

The posterior mediastinum is a subdivision of the mediastinum, the central compartment within the thoracic cavity. It is located posterior to the pericardium and heart, extending from the posterior surface of the heart to the vertebral column. The posterior mediastinum contains various structures, including the esophagus, thoracic aorta, thoracic duct, azygos and hemiazygos veins, sympathetic trunks, vagus nerves, and thoracic splanchnic nerves. Here is a description of the structures and topographic relations within the posterior mediastinum:

1. Esophagus:

• Structure:
  • A muscular tube that connects the pharynx to the stomach.
  • Passes through the posterior mediastinum, running in a relatively straight course.
• Topographic Relations:
  • Lies posterior to the trachea.
  • Anterior to the vertebral column.

2. Thoracic Aorta:

• Structure:
  • The largest artery in the body, carrying oxygenated blood from the heart to the systemic circulation.
  • Descends through the posterior mediastinum.
• Topographic Relations:
  • Lies posterior to the esophagus.
  • Anterior to the vertebral column.

3. Thoracic Duct:

• Structure:
  • The largest lymphatic vessel in the body, responsible for draining lymph from the lower and left sides of the body into the venous system.
  • Ascends through the posterior mediastinum.
• Topographic Relations:
  • Typically lies to the left of the midline.
  • Crosses in front of the vertebral column.

4. Azygos and Hemiazygos Veins:

• Structure:
  • Azygos vein is a major venous vessel that drains into the superior vena cava.
  • Hemiazygos vein is a tributary of the azygos vein.
• Topographic Relations:
  • Azygos vein runs on the right side of the vertebral column.
  • Hemiazygos vein runs on the left side, connecting to the azygos vein.

5. Sympathetic Trunks:

• Structure:
  • Part of the sympathetic nervous system, involved in the fight or flight response.
  • Located on either side of the vertebral column.
• Topographic Relations:
  • Positioned laterally to the vertebral bodies.

6. Vagus Nerves (Cranial Nerve X):

• Structure:
  • Part of the autonomic nervous system, with parasympathetic functions.
  • Travels through the posterior mediastinum.
• Topographic Relations:
  • Located on either side of the esophagus.

7. Thoracic Splanchnic Nerves:

• Structure:
  • Nerve bundles involved in transmitting autonomic signals to abdominal organs.
• Topographic Relations:
  • Run alongside the vertebral column.

Clinical Significance:

• Esophageal Disorders:
  • Conditions affecting the esophagus, such as strictures or tumors, may be evaluated within the posterior mediastinum.
• Aortic Aneurysm:
  • The thoracic aorta passes through the posterior mediastinum, and aneurysms in this region can be a critical clinical concern.
• Thoracic Duct Injury:
  • Trauma or surgical procedures in the posterior mediastinum may pose a risk to the thoracic duct, potentially leading to chyle leaks.
• Neurological Disorders:
  • Disorders involving the vagus nerves or sympathetic trunks may impact autonomic functions.

Understanding the structures and topographic relations within the posterior mediastinum is essential for the evaluation and management of various clinical conditions involving this region of the thoracic cavity.