What is the mediastinum?

The mediastinum is the central compartment of the thoracic cavity, containing all thoracic organs except the lungs. It is bordered laterally by the mediastinal pleura and separates the two pleural cavities.

How is the mediastinum divided?

It is divided by the sternal angle–T4/T5 plane into superior mediastinum and inferior mediastinum. The inferior mediastinum has three parts: anterior, middle, and posterior mediastinum.

What are the boundaries of the mediastinum?

The boundaries are anteriorly the sternum, posteriorly the thoracic vertebrae and intervertebral discs, superiorly the thoracic inlet, inferiorly the diaphragm, and laterally the mediastinal pleura.

What organs and structures are found in the mediastinum?

It contains all thoracic structures except the lungs, including the heart and great vessels (e.g., aorta, SVC), trachea, esophagus, thymus, thoracic duct, nerves (e.g., phrenic, vagus), and lymph nodes.

Why is the mediastinum clinically important?

It is clinically important because its mobility can cause mediastinal shift in conditions like pneumothorax, masses (e.g., thymoma) in the anterior mediastinum may compress structures, and infections (mediastinitis) can spread dangerously near vital organs.

What is the difference between the right and left mediastinal surfaces?

The right surface includes the right atrium, SVC, azygos vein, and phrenic/vagus nerves. The left surface includes the left ventricle, aorta, esophagus, thoracic duct, and phrenic/vagus nerves with the recurrent laryngeal nerve.

How does the mediastinum appear on a chest X-ray?

In a lateral chest X-ray, the area above the sternal angle corresponds to the superior mediastinum, the cardiac shadow represents the middle mediastinum, and areas anterior and posterior to the heart indicate the anterior and posterior mediastinum, respectively.

Mediastinum – Boundaries, Contents & Overview

❓ Frequently Asked Questions