Mediastinum

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Mediastinum
high resolution computed tomography of the thorax, with mediastinum marked in blue.
Mediastinum. The division between superior and inferior is at the sternal angle.
Details
Identifiers
Latin	mediastinum[1]
MeSH	D008482
TA98	A07.1.02.101
TA2	3333
FMA	9826
Anatomical terminology [edit on Wikidata ]

The mediastinum (from

Anatomy

The mediastinum lies within the

The mediastinum can be divided into an upper (or superior) and lower (or inferior) part:

• The superior mediastinum starts at the superior thoracic aperture and ends at the thoracic plane.
• The inferior mediastinum from this level to the diaphragm. This lower part is subdivided into three regions, all relative to the pericardium – the anterior mediastinum being in front of the pericardium, the middle mediastinum contains the pericardium and its contents, and the posterior mediastinum being behind the pericardium.^[6]

The transverse thoracic plane, thoracic plane, plane of Louis or plane of Ludwig is an important anatomical plane at the level of the sternal angle and the T4/T5 intervertebral disc.^[8][9][10] It serves as an imaginary boundary that separates the superior and inferior mediastinum.^[8][9][10]

A number of important anatomical structures and transitions occur at the level of the thoracic plane, including:

• The
  bronchi
  .
• The
  pulmonary trunk
  below.
• The starting of the cardiac plexus.
• The azygos vein arching over the right main bronchus and joining into the superior vena cava.
• The thoracic duct crossing the midline from right to left behind the esophagus
• The end of the pretracheal and prevertebral fasciae.

Superior mediastinum

The superior mediastinum is bounded:

• superiorly by the
  thoracic inlet, the upper opening of the thorax
  ;
• inferiorly by the transverse thoracic plane. which is an imaginary plane passing from the sternal angle anteriorly to the lower border of the body of the 4th thoracic vertebra posteriorly;
• laterally by the pleurae;
• anteriorly by the
  manubrium
  of the sternum;
• posteriorly by the first four thoracic
  vertebral bodies
  .

Contents

Contents muscles origins of the Sternothyreoidei lower ends of the Longi colli arteries aortic arch brachiocephalic artery thoracic portions of the left common carotid and the left subclavian veins brachiocephalic veins and upper half of the superior vena cava left highest intercostal vein nerves vagus nerve cardiac nerve superficial and deep cardiac plexuses phrenic nerve left recurrent laryngeal nerve trachea with paratracheal and tracheobronchial lymph nodes esophagus thoracic duct remains of the thymus some lymph glands anterior longitudinal ligament

Inferior mediastinum

Anterior inferior mediastinum

Is bounded:

• laterally by the
  pleurae
  ;
• posteriorly by the pericardium;^[4]
• anteriorly by the
  costal cartilages
  .

Middle inferior mediastinum

Bounded:

• Anteriorly by (from above downwards): bifurcation of trachea; pulmonary vessels; fibrous pericardium and posterior sloping surface of diaphragm
• Inferiorly by the thoracic surface of the
  diaphragm
  (below);
• Superiorly by the transverse thoracic plane;
• Posteriorly by the bodies of the
  thoracic vertebra (behind);^[4]
• Laterally by the
  mediastinal pleura
  (on either side).

• 
  A transverse section of the

  posterior mediastinum

  .

Clinical significance

The mediastinum is frequently the site of involvement of various

• Anterior mediastinum: substernal
  goiters, lymphoma, thymoma, and teratoma
  .
• Middle mediastinum: lymphadenopathy, metastatic disease such as from small cell carcinoma from the lung.
• Posterior mediastinum: Neurogenic tumors, either from the nerve sheath (mostly benign) or elsewhere (mostly malignant).

Mediastinitis is inflammation of the tissues in the mediastinum, usually bacterial and due to rupture of organs in the mediastinum. As the infection can progress very quickly, this is a serious condition.

A widened mediastinum can be indicative of several pathologies:[12]^[13]

• aortic aneurysm^[14]
• aortic dissection^[15]
• aortic unfolding
• aortic rupture
• hilar lymphadenopathy
• anthrax inhalation - a widened mediastinum was found in 7 of the first 10 victims infected by anthrax (Bacillus anthracis) in 2001.^[16]
• esophageal rupture - presents usually with pneumomediastinum and pleural effusion. It is diagnosed with water-soluble swallowed contrast.
• mediastinal mass
• mediastinitis
• cardiac tamponade^[17]
• pericardial effusion
• thoracic vertebrae fractures
  in trauma patients.

See also

• Mediastinum testis (unrelated structure in the scrotum)
• Mediastinal germ cell tumor
• Mediastinitis
• Mediastinal tumor
• List of anatomy mnemonics#Mediastinum

References

This article incorporates text in the public domain from page 1090 of the 20th edition of Gray's Anatomy (1918)

External links

Look up mediastinum in Wiktionary, the free dictionary.

• Anatomy figure: 21:01-03 at Human Anatomy Online, SUNY Downstate Medical Center – "Divisions of the mediastinum."
• Anatomy figure: 21:02-03 at Human Anatomy Online, SUNY Downstate Medical Center – "The anatomical divisions of the inferior mediastinum."
• thoraxlesson3 at The Anatomy Lesson by Wesley Norman (Georgetown University) – "Subdivisions of the Thoracic Cavity"