Save Google Search id8tr mediastinum Save Google Search id8tr mediastinal Save Google Search id8tr transthoracic Ontology Missing ontology. Save terms here (click "save" or drag them) Download Definition The space in the chest between the pleural sacs of the lungs that contains all the tissues and organs of the chest except the lungs and pleurae Sayings and Phrases with /mediastinum < > Flip Quotes No quotes to show.