MD & DO Is the mediastinum an airtight cavity or is it just a defined imaginary area?


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Jan 24, 2017
The Commonwealth
  1. Pre-Medical
I've always wondered but I have to propose a new medical device (you have to at the end of this class I'm taking, where you pitch it to BMEngineers. I doubt they're really expecting anything actually worthwhile from undergrads but I thought why not take it seriously and see what comes of it.)

Specifically what I am asking is there a physical partition between the heart and the lungs, and I don't mean the pericardium. If so is the cavity airtight (between the heart and lungs,) is it strong? My anatomy textbook and essential anatomy app don't show anything there, and a thoracotomy video I saw once seemed like the thorax was just one big cavity - but for some reason I feel like I recall an old EMS instructor referring to it as its own separate cavity.

Thanks :)
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Aug 31, 2012
  1. Medical Student
This question gave me a moment of "ugh, I still don't know anything" before turning to the trusty wikipedia: Mediastinum - Wikipedia

Sounds like it is defined more or less as the region (not a formal space contained in a sack) between the lungs where the heart and some major vessels hang out.

Is there a physical partition between heart and lungs? Yes. The pleura of the lungs and the pleura of the heart (what we call pericardium). But there's also a potential space between the two that would be considered within the mediastinum, like @OnePunchBiopsy explained.


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7+ Year Member
Jun 11, 2013
  1. Attending Physician
It is a cavity filled with a thin (not visible) layer of fluid, much like how the lung is adhered to the costal pleura.

From outside in, I believe it goes:

Mediastinal pleura ---> Mediastinal space ----> Pericardium.

It's not a fluid layer, but as you said, there is generally pleural covering the mediastinum between it and the lungs. Anteriorly there's not really anything there, nor posteriorly.
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Psychiatry Resident
7+ Year Member
Aug 2, 2013
New York
  1. Resident [Any Field]
The mediastinum is a true anatomical cavity within the thoracic cavity that contains all organs and major central vessels of the thoracic cavity except the lungs (and diaphragm). It is bounded posteriorly by the thoracic spine; anteriorly by the sternum; laterally by the mediastinal pleura; and inferiorly by the diaphragm. The mediastinum itself can be subdivided into superior, inferior, anterior and posterior subdivisions. Ascending from the superior mediastinum will lead to the deep cervical spaces (retropharyngeal, pretracheal, "danger").

A medical condition that relates to the continuous nature of the mediastinal cavity and deep spaces of the neck is descending necrotizing mediastinitis. It results when an infection deep in the neck, such as a tonsillar abscess, ruptures deep cervical fascia, enters into a deep space in the neck, and descends into the mediastinal cavity.
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