Mediastinum

Mediastinum

It is the medial septum of the thorax between two lungs and include mediastinal pleura.

Boundaries of mediastinum

Anteriorly - Sternum.
Posteriorly - Vertebral column.
Superiorly -Thoracic inlet.
Inferiorly - Diaphragm.
On each side - Mediastinal pleura.

Subdivisions of the mediastinum

Division of mediastinum

Mediastinum divided into two parts...
1. Superior mediastinum
2. Inferior mediastinum
inferior mediastinum further divided into 3 parts...
a. Anterior mediastinum
b. Middle mediastinum
c. Posterior mediastinum

Superior Mediastinum

Boundaries

Anteriorly - Manubrium sterni.
Posteriorly - Upper four thoracic vertebra.
Superiorly - Thoracic inlet.
Inferiorly - An imaginary plane ( passing through the sternal angle and the lower border of 4th thoracic vertebra).
On each side - Mediastinal pleura.

Contents

1. Trachea and oesophagus.

2. Muscles - Origin of ...(i. Sternohyoid, ii.Sternothyroid, iii. Lower end of longus colli ).

3. Arteries -( i. Arch of aorta, ii. Brachiocephalic artery, iii. Left common carotid artery, Left subclavian artery ).

4. Veins -( i. Right and left brachiocephalic veins, ii. Upper half of the superior vena cava, iii. Left superior intercostal vein ).

5. Nerves - ( i. Vagus, ii. Phrenic, iii. Cardiac nerves of both side, iv. Left recurrent laryngeal nerve ).

6. Thymus.

7. Thoracic duct.

8. Lymph nodes.

Anterior Mediastinum

It is a very narrow space in front of pericardium.
It is continue to the superior mediastinum.

Boundaries

Anteriorly - Body of sternum.
Posteriorly - Pericardium.
Superiorly - an imaginary line passing through the sternal angle and the lower border of 4th thoracic vertebra ( inferior border of superior mediastinum ).
Inferiorly - Diaphragm.
On each side - Mediastinal Pleura.

Contents

1. Sternopericardial ligaments.

2. Lymph nodes with lymphatics.

3. Small mediastinal branches of internal thoracic artery.

4. The lowest part of the thymus.

5. Areolar tissue.

Middle Mediastinum

Boundaries

Anteriorly - Sternopericardial ligaments ( Posterior border of anterior mediastinum).
Posteriorly - Anterior border of the posterior mediastinum.
Superiorly - Lower border of superior mediastinum.
Inferiorly - Diaphragm.
On each side - Mediastinal pleura.

Contents

1. Heart and pericardium.

2. Arteries - ( i. Ascending aorta, ii. Pulmonary trunk, iii. Two pulmonary arteries ).

3. Veins - ( i. Lower half of superior vena cava, ii. Terminal part of azygos vein, iii. Right and left pulmonary vein ).

4. Nerves - ( i. Phrenic nerves, ii. Deep cardiac plexus ).

5. Lymph nodes - Tracheobronchial lymph nodes.

6. Right and left principal bronchi.

Posterior Mediastinum

Boundaries

Anteriorly - Pericardium and bifurcation of trachea ( Posterior border of middle mediastinum).
Posteriorly - Lower eight thoracic vertebra.
Superiorly - Lower border of superior mediastinum.
Inferiorly - Diaphragm.
On each side - Mediastinal pleura.

Contents

1. Oesophagus.

2. Descending aorta.

3. veins - ( i. Azygos, ii. Hemiazygos, iii. Accessory hemiazygos ).

4. Nerves - ( i. Vagus, ii. Splanchnic nerves ).

5. Lymph nodes - ( i. Posterior medistinal lymph node, ii. Thoracic duct  ).

Applied

1. Mediastinal syndrome.
2. Mediastinal shift.