mediastinum

[mee-dee-a-stahy-nuhm]
noun, plural mediastina [mee-dee-a-stahy-nuh] . Anatomy.
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.

Origin:
1535–45; < Neo-Latin; compare mediastīnus of middle class, apparently identical with Latin mediast(r)īnus a low-ranking slave, perhaps derivative of medius mid1, though sense and formation unclear

mediastinal, adjective
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World English Dictionary
mediastinum (ˌmiːdɪəˈstaɪnəm)
 
n , pl -na
1.  a membrane between two parts of an organ or cavity such as the pleural tissue between the two lungs
2.  the part of the thoracic cavity that lies between the lungs, containing the heart, trachea, etc
 
[C16: from medical Latin, neuter of Medieval Latin mediastīnus median, from Latin: low grade of servant, from medius mean]
 
medias'tinal
 
adj

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American Heritage
Medical Dictionary

mediastinum me·di·as·ti·num (mē'dē-ə-stī'nəm)
n. pl. me·di·as·ti·na (-nə)

  1. A septum between two parts of an organ or a cavity.

  2. The region in mammals between the pleural sacs, containing the heart and all of the thoracic viscera except the lungs. Also called interpleural space, mediastinal space.


me'di·as·ti'nal (-nəl) adj.
The American Heritage® Stedman's Medical Dictionary
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Encyclopedia Britannica
Encyclopedia

mediastinum

the 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

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
The mediastinum testis extends from the upper to near the lower extremity of the gland, and is wider above than below.
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