Posterior mediastinum

Posterior Mediastinum

The Posterior Mediastinum is an anatomical region in the thoracic cavity, located behind the heart and between the two pleural cavities containing the lungs. It is one of the three parts of the mediastinum, the others being the anterior mediastinum and the middle mediastinum.

Anatomy

The posterior mediastinum is bounded by the posterior pericardium and the diaphragm on the front, the spine on the back, and the pleural cavities on the sides. It extends from the level of the fourth thoracic vertebra down to the twelfth thoracic vertebra.

The posterior mediastinum contains several important structures, including the esophagus, the thoracic duct, the aorta and its branches, the azygos vein and its tributaries, the vagus nerve, and the sympathetic trunk.

Structures

Esophagus

The esophagus is a muscular tube that carries food from the pharynx to the stomach. In the posterior mediastinum, it lies to the right of the midline and anterior to the aorta.

Thoracic Duct

The thoracic duct is the largest lymphatic vessel in the body. It drains lymph from the entire body, except the right upper quadrant, into the venous system.

Aorta

The aorta is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen. The descending part of the aorta that lies within the posterior mediastinum is known as the thoracic aorta.

Azygos Vein

The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava. It can provide an alternative path for blood to return to the heart if the inferior or superior vena cava is blocked.

Vagus Nerve

The vagus nerve is the tenth cranial nerve, and it has the most extensive distribution of the cranial nerves. It provides parasympathetic innervation to almost all of the thoracic and abdominal viscera, except the adrenal glands.

Sympathetic Trunk

The sympathetic trunk is a part of the sympathetic nervous system, running along the vertebral column. It allows nerve fibres to travel to spinal nerves that are superior and inferior to the one in which they originated.

Clinical Significance

Diseases that can affect the posterior mediastinum include mediastinitis, which is inflammation of the tissues in the mediastinum, and various types of mediastinal tumors. Diagnosis of these conditions often involves imaging studies such as computed tomography (CT) or magnetic resonance imaging (MRI).