The Mediastinum
The mediastinum is the central compartment of the thoracic cavity, located between the two pleural sacs. It is clinically divided by the transverse thoracic plane (an imaginary line from the sternal angle to the T4/T5 intervertebral disc).
Divisions and Contents
| Division | Key Contents |
|---|---|
| Superior | Great vessels (aortic arch), trachea, esophagus, thymus, thoracic duct, vagus/phrenic nerves. |
| Inferior – Anterior | Thymus remnants, lymph nodes, connective tissue. |
| Inferior – Middle | Heart, pericardium, roots of great vessels, phrenic nerves. |
| Inferior – Posterior | Descending aorta, esophagus, azygos system, thoracic duct, vagus nerves. |
High-Yield Exam Pearl:
The transverse thoracic plane is a vital landmark. At this level: the trachea bifurcates (carina), the aortic arch begins and ends, the azygos vein enters the SVC, and the thoracic duct crosses from the right to the left side of the esophagus.