- mediastinum
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—mediastinal, adj.1. a median septum or partition between two parts of an organ, or paired cavities of the body.2. the partition separating the right and left thoracic cavities, formed of the two inner pleural walls, and, in humans, comprising all the viscera of the thorax except the lungs.[1535-45; < NL; cf. mediastinus of middle class, appar. identical with L mediast(r)inus a low-ranking slave, perh. deriv. of medius MID1, though sense and formation unclear]
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▪ anatomythe anatomic region located between the lungs that contains all the principal tissues and organs of the chest except the lungs. It extends from the sternum, or breastbone, back to the vertebral column and is bounded laterally by the pericardium, the membrane enclosing the heart, and the mediastinal pleurae, membranes that are continuous with those lining the thoracic cage. The mediastinum is a division of the thoracic cavity; it contains the heart, thymus gland, portions of the esophagus and trachea, and other structures. For clinical purposes it is traditionally divided into the anterior, middle, posterior, and superior regions.* * *
Universalium. 2010.