The Mediastinum
Prof.Dr.Abduljabar AlhubaityHead Dep.of Anatomy,Histology& Embryology
College of Medicine/ Mosul University
Mosul / IRAQ
10th April 2017
The Mediastinum can be defined as the space
Occupied by a septum of connective tissueEmbedded in it so many structures as nerves,
Vessels, lymphatics & lymph nodes and so
This space is enclosed between the medial surface of the 2 lungs (on each side ), middle part of the inlet of the thorax ( above ) and
The middle part of the outlet of the thorax (below) ,between the back of the sternum (anteriorly) and in front of the all the 12 thoracic vertebrae ( posteriorly ).
It is subdivided by an imaginary plane passing
Between the sternal angle (anteriorly ) and the intervertebral disc between 4th thoracic vertebra( T 4 ) & the 5th thoracic vertebra (T5).
Into a superior mediastinum just above this imaginary plane & an inferior mediastinum just below this imaginary plane. The inferior
Mediastinum is subdived into 3 parts by the presence of the pericardium containing the heart ( This is middle one).The space infront of it (anterior one )& the part behind pericardium and infront of the lower 8 thoracic vertebrae (T5-T12)is the posterior mediastinum .
The Superior Mediastinum
The superior mediastinum contains the followings:1-The Arch of the Aorta & the 3 main As arising from it ( L.subclavian,L common carotid & the
Brachiocephalic Trunk on the right side ( it gives
The R.Subclavian & R. Common Carotid As ).
2-The The R.& L. vagi Nerves .
3-The R& L Phrenic Nerves ( C3-C5).
4-The R & L subclavian Veins (unite to form S.V.C)
5-The upper half of the Superior vena cava (S.V.C)
6-The R & L Sympathetic trunks.
7-The Thymus gland in children.
8-The lymph nodes & vessels embedded in it.
9-The Trachea.10-The Esophagus.
11-The Left. recurrent laryngeal nerve running in
The groove between the trachea & esophagus .
12-The Thoracic duct.
13-The arch of tha Azygoes vein as it arches to reach the superior vena cava.
The Middle Mediastinum
It contains the following structures:1-The Pericardium containing the Heart inside it.
2-The Ascending Aorta.
3-The Pulmonary Trunk.
4-The lower half of the Superior Vena Cava.
5-The terminal part of the Inferior Vena Cavas .
6- The root of the lung on each side (contains so
Many structures as A.,V., Bronchus & lymphatics).
7-The R.&L. Phrenic Nerve running on each side.
8-The Pericardiophrenic vessels parallel to the
Phrenic Nervs on each side.
The Posterior Mediastinum
Is the Space posterior to the pericardium(contains the Heart ) & the sloping part of the diaphragm.The space lies anterior to the lower 8 thoracic vertebrae ( T5-T12).It contains :1-The Esophagus.
2-The Descending thoracic Aorta.
3-The The Esophageal Plexus of nerve on surface of
The Esophagus ( represents R .& L. Vagi Nerves).
4-The Thoracic Duct.
5-The Azygoes venous system .
6-The R.&L. Sympathetic Nerves.
7-The posterior mediastinal Lymph node groups.
The Anterior Mediastinum
It encloses between the back of the body of the Sternum (infront ) & anterior to the Pericardium(behind).It contains the following structures:
1-The lower part of the Thymus in children may reach the upper part of anterior mediastinum.
2-Superior & Inferior Sternopericardial ligaments.
3-Anterior mediastinal lymph nodes group.
4-The internal thoracic (internal mammary) vessels
Just behind the costal cartilages on each side of the body of the sternum.
