Mediastinum

**Semantic type:** Body Part, Organ, or Organ Component

**Definition:** An anatomic site along the midline and under the sternum that contains the heart and pericardium, the bases of the great vessels, the trachea and bronchi, esophagus, thymus, lymph nodes, thoracic duct, phrenic and vagus nerves, and other structures and tissues.

**Synonyms:** - MEDIASTINUM - Mediastinal structure (body structure) - Mediastinum, NOS - mediastinal part of chest - mediastinum - mediastinum