Human Anatomy - Kotsan I. Ya. 2009

Respiratory System
Mediastinum

The mediastinum (mediastinum) is a space located in the middle of the thoracic cavity between the right and left pleural sacs, housing a complex of vital Organs. It is bounded anteriorly by the Sternum, posteriorly by the thoracic Vertebral Column, laterally by the mediastinal Pleura, and inferiorly by the Diaphragm. Superiorly, it extends to the level of the superior thoracic aperture.

The mediastinum is subdivided into the superior mediastinum (mediastinum superius) and inferior mediastinum (mediastinum inferius). The imaginary horizontal plane serving as the boundary between them runs from the junction of the manubrium and body of the sternum (anteriorly) to the intervertebral disc between the fourth and fifth thoracic vertebrae (posteriorly). The superior mediastinum contains the Thymus, right and left brachiocephalic Veins, aortic arch and its major branches (brachiocephalic trunk, left common carotid artery, and left Subclavian Artery), part of the Trachea, the upper part of the thoracic Esophagus, as well as portions of the Thoracic duct, sympathetic trunks, vagus nerves, and phrenic nerves. Based on its relation to The Heart, the inferior mediastinum is divided into three compartments: anterior, middle, and posterior.

The anterior mediastinum (mediastinum anterius) lies between the anterior wall of the Pericardium and the sternal body. It contains the internal thoracic Arteries and veins, along with anterior mediastinal and parasternal Lymph Nodes AND their connecting vessels.

The middle mediastinum (mediastinum medium) houses the pericardium enclosing The Heart and the intrapericardial segments of the great vessels, main Bronchi, pulmonary arteries and veins, phrenic nerves, and lower tracheobronchial and lateral pericardial lymph nodes.

The posterior mediastinum (mediastinum posterius) is situated between the posterior wall of the pericardium anteriorly and THE VERTEBRAL COLUMN posteriorly. It transmits the Thoracic Aorta, azygos and hemiazygos veins, sympathetic trunks, splanchnic nerves, vagus nerves, esophagus, and thoracic duct. In addition, the posterior mediastinum contains posterior mediastinal and prevertebral lymph nodes.

According to the Basle Nomina Anatomica, and frequently in clinical practice, the mediastinum is divided into anterior and posterior compartments (mediastinum anterius et mediastinum posterius), separated by an imaginary coronal plane passing through the trachea and the roots of the Lungs. Under this Classification, the anterior mediastinum contains the heart with the great vessels entering and leaving it, pericardium, aortic arch, thymus, phrenic nerves, internal thoracic vessels, and parasternal, mediastinal, and superior diaphragmatic lymph nodes. The posterior mediastinum contains the esophagus, thoracic aorta, thoracic duct, azygos and hemiazygos veins, vagus and splanchnic nerves, sympathetic trunks, and posterior mediastinal and prevertebral lymph nodes.