The mediastinum is located in the middle of the thoracic cavity and contains the heart, great vessels, trachea, esophagus, and thymus gland. It is divided into superior and inferior portions by an imaginary line passing from the sternal angle to the fourth thoracic vertebrae. The inferior mediastinum is further divided into the anterior, middle, and posterior mediastinum. The document outlines the contents and clinical correlations of mediastinal infections, tumors, cysts, and the diagnostic procedure of mediastinoscopy.

1. Dr. Soran M Karim

3. References
Clinical anatomy by
regions, 10th edition,
Richard Snell's; pages
193-221
Netters atlas with
clinical correlations 5th
edition, pages 200-216.

8. Mediastinum:
• The mediastinum is located in
the middle of the thoracic cavity.
• The main contents include the
heart, trachea, esophagus, great
vessels, and thymus gland. The
mediastinum is lined mainly by
the parietal pleura.
• The mediastinum also contains
another cavity called the
pericardial cavity.
• The pericardial cavity surrounds
the heart and roots of the great
vessels.

11. Sub divisions
• Divided in superior and inferior
divisions by imaginary line
passing from the sternal angle
anteriorly to the lower border of
the 4th thoracic vertebrae.
• The inferior mediastinum is
further subdivided into the
middle mediastinum, which
consists of the pericardium and
heart, the anterior
mediastinum, which is a space
between the pericardium and the
sternum and the posterior
mediastinum, which lies
between the pericardium and the
vertebral column.

13. Superior mediastinum
• The superior mediastinum is the
region sandwiched between the
pleural sac on each side above an
imaginary line from the angle of
Louis in front to the fourth/fifth
thoracic intervertebral disc behind.
• Its important contents are the
oesophagus, trachea, great
veins, aortic arch and its branches, the
vagus, phrenic and left recurrent
laryngeal nerves, the upper part of
the thoracic duct and the thymus
gland.

16. Inferior mediastinum
Inferior mediastinum – extends
downwards, terminating at the
diaphragm.
It is further subdivided into the
anterior mediastinum, middle
mediastinum and posterior
mediastinum.

20. POSTERIOR MEDIASTINUM
CONTENTS:
1. Esophagus (most anterior structure)
2. Thoracic duct
3. Right & left vagus
4. Descending aorta
5. Azygos & hemiazygos veins
6. Right & left sympathetic trunks & their branches (splanchnic
nerves)
7. Lymph nodes

22. Clinical correlations
• Mediastinitis
Deep infection of the neck spread readily into the thorax, producing
a mediastinitis.
Penetrating wounds of the chest involving the esophagus may
produce a mediastinitis.

24. Clinical correlations; cont.
Deflection of Mediastinum
If air enters the pleural cavity (a
condition called pneumothorax),
the lung on that side immediately
collapses and the mediastinum is
displaced to the opposite side.
patient’s being breathless and in a
state of shock; on examination, the
trachea and the heart are found to
be displaced to the opposite side

25. Clinical correlations; cont
• Mediastinal Tumors or Cysts
Enlargement of mediastinal tumor
may compress the left recurrent
laryngeal nerve, producing
paralysis of the left vocal fold.
An expanding cyst or tumor can
partially occlude the superior vena
cava, causing severe congestion of
the veins of the upper part of the
body.
Other pressure effects can be seen
on the sympathetic trunks, phrenic
nerves, and sometimes the
trachea, main bronchi, and
esophagus.

26. Clinical correlations; cont
• Mediastinoscopy
diagnostic procedure by which
tracheobronchial lymph nodes are
obtained without opening the pleural
cavities.
A small incision is made in the
midline in the neck just above the
suprasternal notch, and the
superior mediastinum is explored
down to the region of the
bifurcation of the trachea.
The procedure can be used to
determine the diagnosis and
degree of spread of carcinoma of
the bronchus.

27. Summary
• Mediastinum: definition
• Boundaries and extensions
• Sub divisions
• Contents

28. Upcoming lecture; next week
• The heart and
pericardium
• Clinical anatomy
by region
• Chapter 4 ; pages
192-217