Mediastinum

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mediastinum

[‚mē·dē·ə′stī·nəm]
(anatomy)
A partition separating adjacent parts.
The space in the middle of the chest between the two pleurae.

Mediastinum

 

in man, an anatomic area in the thoracic cavity, bounded anteriorly by the sternum, posteriorly by the thoracic region of the spine, laterally by the pleurae and lung surfaces, and inferiorly by the diaphragm; an arbitrary horizontal line drawn across the upper edge of the sternum is considered to be the upper boundary.

A distinction is made between anterior and posterior mediastinal regions, which are divided by the roots of the lungs. The anterior mediastinum contains the heart and heart sac (the pericardium), the ascending aorta and its arch (including the arteries issuing from them), the pulmonary trunk, the venae cavae, the pulmonary veins, and the phrenic nerves. The posterior mediastinum contains the thoracic portion of the descending aorta and its branches, the esophagus, the azygos and hemiazygos veins, the thoracic lymphatic duct, and the vagus and splanchnic nerves.

Closed injuries of mediastinal organs occur in cases of contusions, compression of the chest, and sternal fractures. Upon injury to the lungs or bronchi and the accumulation of air, pneumomediastinum and the compression of mediastinal organs may occur. Open mediastinal injuries are associated with injuries of the lungs and often of the organs of the abdominal cavity. Mediastinal injuries are treated surgically. The most common diseases of the mediastinum include mediastinitis, substernal extension of an enlarged thyroid gland, cysts and tumors of mediastinal organs, and lesions of mediastinal lymph nodes, for example, in cases of lymphogranulomatosis.

REFERENCES

Petrovskii, B. V. Khirurgiia sredosteniia. Moscow, 1960.
Elizarovskii, S. I., and G. I. Kondrat’ev. Khirurgicheskaia anatomiia sredosteniia (atlas). Moscow, 1961.
Gol’bert, Z. V., and G. A. Lavnikova. Opukholi i kistv sredosteniia. Moscow, 1965. ’