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MEDIASTINUM

 

DEFINE MEDIASTINUM. DESCRIBE THE SUPERIOR MEDIASTINUM UNDER THE FOLLOWING HEADINGS: (A) BOUNDARIES (B) CONTENTS (C) APPLIED ASPECT. (LE)

DIVISION OF MEDIASTINUM AND NAME THE CONTENTS OF SUPERIOR MEDIASTINUM? (SE)

SUPERIOR MEDIASTINUM- BOUNDARIES AND CONTENTS. (SA)

Mediastinum is the space in the thoracic cavity in between the two pleural cavities

Divisions of the mediastinum

Mediastinum is divided into superior and inferior mediastinum by an imaginary plane passing through sternal angle ( anteriorly) and the lower border of 4TH thoracic vertebra ( posteriorly).

The inferior mediastinum is further divided into anterior, middle and posterior mediastinum.

It is divided by the pericardium which occupies the middle mediastinum.

The part of mediastinum in front of the pericardium is anterior mediastinum, and that behind the pericardium is the posterior mediastinum.

Superior mediastinum

Boundaries:-

Anteriorly- manubrium sterni Posteriorly- upper four thoracic vertebra

Inferiorly- by an imaginary plane passing through sternal angle ( anteriorly) and the lower border of 4TH thoracic vertebra ( posteriorly).

On each side- mediastinal pleura

Contents

Arteries

1)arch of aorta

2)brachioephalic artery

3)left comman carotid artery

4)left subclavian artery

Veins

1)right and left brachiocephalic veins

2 ) upper half of superior venacava 3)left superior intercostal vein

Nerves Phrenic nerves vagus nerves

sympathetic trunks and cardiac nerves left recurrent laryngeal nerve

Trachea and oesophagus Muscles-

origins of sternhyoid , sternothyroid Thymus

Thoracic duct Lymph nodes-

Applied aspects

Mediastinitis-

The prevertebral layer and pre tracheal layer of deep cervical fascia extend to the superior mediastinum. Hence neck infections between these fasciae can spread into the superior mediastinum.

In the superior mediastinum all large veins are on the right side and arteries on the left side. thus there is much dead space on the right side and it is into this space that tumour or cysts tend to project.

Mediastinal syndrome-

Compression of mediastinal structures by any tumours or cysts give rise to a group of symptoms known as mediastinal syndrome.

Causes

Bronchogenic carcinoma, Hodgkins disease, aortic aneurysm.

Clinical features

Engorgement of veins in the upper half of the body- due to obstruction of superior venacava. Dyspnea( difficulty in breathing) – due to compressin of trachea

Dysphagia- due to compression of esophagus

Dysphonia- - due to compression of recurrent laryngeal nerve. Intercostal neuralgia- due to pressure on the intercostal nerves

DEFINE MEDIASTINUM. MENTION THE CONTENTS OF POSTERIOR MEDIASTINUM. DESCRIBE THE THORACIC PART OF OESOPHAGUS. ADD A NOTE ON ITS APPLIED ANATOMY. (LE)

Mediastinum is the space in the thoracic cavity in between the 2 pleural cavities.

Mediastinum is divided into superior and inferior mediastinum by an imaginary plane passing through sternal angle ( anteriorly) and the lower border of 4TH thoracic vertebra ( posteriorly).

Contents of posterior mediastinum:-

Oesophagus

Arteries-

descending thoracic aorta and its branches

Veins

Azygos vein Hemiazygos vein Accessory hemiazygos vein

Nerves Vagus

Splanchnic nerves- greater, lessor and least Sympathetic trunk

Thoracic duct and posterior mediastinal lymph nodes.

structures in the posterior mediastinum

Oesophagus Arteries

descending thoracic aorta and its branches

Veins

Azygos vein Hemiazygos vein Accessory hemiazygos vein

Nerves Vagus

Splanchnic nerves- greater, lessor and least Sympathetic trunk

Thoracic duct and posterior mediastinal lymph nodes.

Oesophagus is a 25 cm long muscular tube connecting the pharynx to the stomach. It is divided into 3 parts:-

Cervical part Thoracic part Abdominal part

The thoracic part extends from superior border of manubrium sterni to the oesophageal opening in the diaphragm.

Relations of thoracic part of oesophagus Anteriorly ( from above downwards)

Trachea

Arch of aorta

Right pulmonary artery

Left principal bronchus

Left atrium enclosed in pericardium

Diaphragm

Posteriorly

Vertebral column

Right posterior intercostals arteries

Thoracic duct

Azygos vein

Hemiazygos veins

Descending thoracic aorta

To the right

Right lung and pleura

Azygos vein

Right vagus nerve

To the left

Arch of aorta

Left subclavian artery

Thoracic duct

Left lung and pleura

Left recurrent laryngeal nerve

Descending thoracic aorta

Blood supply

Arteries

Oesophageal branches of Descending thoracic aorta

Bronchial arteries

Venous drainage

Azygos vein

Hemiazygos vein

Lymphatic drainage

To Posterior mediastinal lymph nodes.

Applied aspect

Oesophagoscopy- is performed to visualise the interior of oesophagus. Malignant tumours of oesophagus are more comman in the lower 1/3rd.

Posterior mediastinum- boundaries and contents.

Boundaries of posterior mediastinum:-


Anteriorly –

Pericardium Bifurcation of trachea Pulmonary vessels

Posterior part of the upper surface of diaphragm Posteriorly –

Lower eight thoracic vertebrae and intervening discs On each side -

mediastinal pleura

Contents of posterior mediastinum

Oesophagus

Arteries-

Descending thoracic aorta and its branches

Veins

Azygos vein

Hemiazygos vein

Accessory hemiazygos vein

Nerves

Vagus

Splanchnic nerves- greater, lessor and least

Sympathetic trunk

Thoracic duct and posterior mediastinal lymph nodes

ANTERIOR MEDIASTINUM- BOUNDARIES AND CONTENTS (SA) Boundaries

Anteriorly – body of sternum Posteriorly – pericardium

Superiorly – imaginary plane separating the superior from inferior mediastinum. Inferiorly - superior surface of diaphragm

On each side - mediastinal pleura

Contents

Sternopericardial ligaments

Lymph nodes with lymphatics

Mediastinal branches of internal thoracic artery

Lower portion of thymus (in children)

Areolar tissue.

MIDDLE MEDIASTINUM - CONTENTS (SA)

Contents of middle mediastinum are- heart

Pericardium

Arteries- ascending aorta, pulmonary trunk

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Veins- superior venacava, azygos vein Nerves – phrenic nerve, deep cardiac plexus Lymph nodes- tracheobronchial Bifurcation of trachea

Posterior mediastinum- contents

Contents of posterior mediastinum are:- Oesophagus

Arteries-

Descending thoracic aorta and its branches Veins

Azygos vein Hemiazygos vein Accessory hemiazygos vein

Nerves Vagus

Splanchnic nerves- greater, lessor and least Sympathetic trunk

Thoracic duct and posterior mediastinal lymph nodes

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