Mediastine
Mediastine , noun
[New Latin mediastinum, from Latin medius middle; compare mediastinus helper, a menial servant, Late Latin mediastinus equiv. to medius: cf French médiastin.]
(Anatomy) A partition; a septum; specifically, the folds of the pleura (and the space included between them) which divide the thorax into a right and left cavity. The space included between these folds of the pleura, called the mediastinal space, contains the heart and gives passage to the esophagus and great blood vessels.
Also: Mediastinum