QS Study

The middle mediastinum is an artificial space of the mediastinum divided from the remainder of the extra-pleural intrathoracic cavity by arbitrary lines. It contains most of the thoracic organs and acts as a conduit for structures traversing the thorax on their way into the abdomen. It forms the largest component of the inferior mediastinum.

Middle mediastinum Boundaries

Anteriorly: Fibrous pericardium.

Posteriorly: Pericardium & associated structures, which forms the anterior wall of the posterior mediastinum (Bifurcation of the trachea, Pulmonary vessels, Fibrous pericardium, Posterior part of upper surface of the diaphragm).

On each side: Mediastinal pleura separated by the pericardium.

Inferiorly: a Superior surface of the diaphragm with intervening pericardium.

Superiorly: Imaginary plane passing through the sternal angle.

Fig: Boundaries and Contents of Middle Mediastinum

Contents – Heart enclosed in the pericardium. The middle mediastinum is the major subdivision of the inferior mediastinum. The main contents of middle mediastinum are pericardium and its contents (example, the heart, and roots of its great vessels). It contains some significant organs, vessels, nerves, and lymphatic structures.

(i) Arteries:

  1. Ascending aorta.
  2. Pulmonary trunk.
  3. Two pulmonary arteries.

(ii) Veins:

  1. The lower half of superior vena cava.
  2. The terminal part of the azygos vein.
  3. Right & left pulmonary veins.

(iii) Nerves:

  1. Phrenic nerve.
  2. Deep cardiac plexus.

(iv) Lymph nodes: Tracheobronchial nodes.

(v) Tubes:

  1. Bifurcation of the trachea.
  2. Right & left principal bronchi.