QS Study

The mediastinum is a space in between two pleural sacs and their contained lungs. It is a membranous partition between two body cavities or two parts of an organ, especially that between the lungs. The organs include the heart and its large veins and arteries, the trachea, the esophagus, the bronchi, and lymph nodes.

Division

The mediastinum is divided into superior and inferior mediastinum by an imaginary plane passing through the sternal angle (anteriorly) and the lower border of the body of the 4th thoracic vertebra (Posteriorly). Again, the inferior mediastinum is subdivided into three parts by the pericardium. The area infront of the pericardium is the anterior mediastinum. The area behind the pericardium is the posterior mediastinum. The pericardium and its contents from the middle mediastinum.

Fig: Mediastinum Boundaries

Superior mediastinum:

Boundaries

Anteriorly: Manubrium sterni.

Posteriorly: Upper 4 thoracic vertebrae with intervening intervertebral discs.

Superiorly: Plane of the thoracic inlet.

Inferiorly: An imaginary plane passing through the sternal angle infront & the lower border of 4th thoracic vertebra behind.

On each side: Mediastinal pleura.

Contents

Viscera:

a) Trachea.

b) Oesophagus.

Muscles:

a) Sternohyoid.

b) Sternothyroid.

c) Lower ends of longus colli.

Arteries:

a) Arch of aorta.

b) Brachiocephalic artery.

c) Left subclavian artery.

d) Left common carotid artery.

Veins:

a) Right & left brachiocephalic veins.

b) Upper half of the superior vena cava.

c) Left superior intercostal vein.

Nerves:

a) Vagus nerves.

b) Phrenic nerves.

c) Cardiac nerves.

d) Left recurrent laryngeal nerve.

Lymph nodes: Paratracheal, brachiocephalic and tracheobronchial.