Tuesday 3 May 2022

DIFFERENT PARTS OF THE MEDIASTINUM AND THE CONTENTS

The mediastinum is an area found in the midline of the thoracic cavity that is surrounded by the left and right pleural sacs. It is divided into the superior and inferior mediastinum, of which the latter is larger.
 
SUPERIOR MEDIASTINUM
The superior mediastinum is a space bounded anteriorly by the manubrium of the sternum, and posteriorly by the bodies of T1-T4 vertebrae. Its superior border is an oblique plane extending from the jugular notch of the manubrium to the superior border of T1 vertebra. Whilst the inferior border is a transverse plane extending from the sternal angle to the T4-T5 intervertebral disc.

 

The transverse plane separates the superior from the inferior mediastinum. Lastly, the lateral borders are the mediastinal surfaces of parietal pleura on each side.

 

Contents of the superior mediastinum are:

Thymus

Trachea

Esophagus

Aortic arch

Brachiocephalic trunk

Left common carotid artery

Left subclavian artery

Internal thoracic arteries

Superior vena cava

Left superior intercostal vein

Brachiocephalic veins

Phrenic nerves

Vagus nerves

Left recurrent laryngeal branch of the left vagus nerve

Thoracic duct

Lymph nodes and vessels,

Other small arteries, veins and nerves

 

INFERIOR MEDIASTINUM

The inferior mediastinum extends from the inferior border of the superior mediastinum to the diaphragm. It is subdivided anterior-to-posterior into three spaces:

 

Anterior mediastinum: this is posterior to the body of the sternum and anterior to the pericardium

Middle mediastinum: this is bounded by the pericardium, which encloses the heart and origins of the great vessels

Posterior mediastinum: this posterior to the pericardium and anterior to the vertebrae

 

CONTENTS OF THE INFERIOR MEDIASTINUM

Anterior mediastinum: inferior portion of thymus, fat, connective tissue, lymph nodes, mediastinal branches of internal thoracic vessels, sternopericardial ligaments

 

Middle mediastinum: pericardial sac, heart, origins of great vessels like pulmonary trunk, ascending aorta, pulmonary veins; superior vena cava, inferior vena cava

tracheal bifurcation and main bronchi

 

Posterior inferior mediastinum: descending thoracic aorta, azygos veins, hemiazygos veins, accessory hemiazygos veins, thoracic duct, cisterna chyli, esophagus, esophageal plexus, vagus nerve, greater, lesser and least splanchnic nerves, lymphatics

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