The mediastinum acts as a conduit for structures that pass completely through the thorax from one body region to another and for structures that connect organs in the thorax to other body regions.
The esophagus, vagus nerves, and thoracic duct pass through the mediastinum as they course between the abdomen and neck.
The phrenic nerves, which originate in the neck, also pass through the mediastinum to penetrate and supply the diaphragm.