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 more detailed enumeration of the contents of the posterior mediastinum:
1. Esophagus:
- A muscular tube that carries food and liquids from the pharynx to the stomach.
- Lies in the posterior mediastinum, typically posterior to the trachea.
2. Thoracic Aorta:
- The largest artery in the body, originating from the left ventricle of the heart.
- Descends through the posterior mediastinum, giving rise to various branches that supply the thoracic organs and continue into the abdominal cavity.
3. Thoracic Duct:
- The largest lymphatic vessel in the body.
- Ascends through the posterior mediastinum, carrying lymph from the lower and left sides of the body.
- Drains into the venous system near the junction of the left internal jugular vein and left subclavian vein.
4. Azygos Vein and Hemiazygos Vein:
- Azygos Vein:
- A major venous vessel that ascends on the right side of the vertebral column.
- Drains blood from the posterior thoracic and abdominal walls, as well as the esophagus and bronchi.
- Typically crosses over the vertebral column and enters the superior vena cava.
- Hemiazygos Vein:
- Drains the left side of the posterior thoracic and abdominal walls.
- Connects with the azygos vein.
5. Sympathetic Trunks:
- Part of the sympathetic nervous system, involved in the fight or flight response.
- Located on either side of the vertebral column.
- Consists of ganglia and nerve fibers.
6. Vagus Nerves (Cranial Nerve X):
- A pair of cranial nerves that carry parasympathetic fibers.
- Run alongside the esophagus through the posterior mediastinum.
- Contribute to the innervation of various thoracic and abdominal organs.
7. Thoracic Splanchnic Nerves:
- Nerve bundles involved in transmitting autonomic signals to abdominal organs.
- Consist of greater, lesser, and least splanchnic nerves.
- Pass through the posterior mediastinum en route to the abdominal sympathetic ganglia.
8. Posterior Intercostal Arteries and Veins:
- Arteries and veins that supply and drain the intercostal spaces.
- Originate from and drain into the thoracic aorta and azygos system, respectively.
Clinical Significance:
- Disorders or pathologies affecting the structures in the posterior mediastinum can include esophageal disorders, aortic aneurysms, thoracic duct injuries, neurological disorders related to the vagus nerves or sympathetic trunks, and conditions involving the azygos and hemiazygos veins.
Understanding the contents of the posterior mediastinum is crucial for clinicians, particularly in the evaluation and management of conditions related to this region of the thoracic cavity. Imaging studies such as CT scans and MRIs are often used to visualize these structures and assess for abnormalities or pathology.