1403- Anatomy-Mediastum

What is the mediastinum

The mediastinum is the central compartment of the thoracic cavity, located between the lungs. It contains vital structures such as the heart, trachea, esophagus, and major blood vessels and includes the mediastinal pleura.

Boundaries of the mediastinum

Anteriorly- the sternum

Posteriorly→ Vertebral column

Superiorly→ Thoracic inlet

Inferiorly → Diaphragm

On each side → Mediastinal pleura

Importance of knowing mediastinum boundaries

To monitor infection which can move throughout the mediastinal space as it communictes with both the neck and the retroperitoneum.

Fascial planes connect the mediastinum to other regions( neck and retroperitoneum), allowing for the spread of disease and influencing surgical approaches.

Subdivision- The superior mediastinum

Separated by imaginary plane at the sternal angle anteriorly.

Posteriorly- lower body of the fourth thoracic vertebra and extends to the thoracic inlet.

Subdivision - the inferior mediastinum

Separated into the middle, posterior and anterior mediastinum by the pericardium.

Anterior mediastinum

Subdivision of the inferior mediastinum.

Area in front of the pericardium, overlapped by thin anterior borders of both lungs.

Posterior mediastinum

Subdivision of the inferior mediastinum.

Area behind the pericardium.

Middle mediastinum

subdivision of the inferior mediastinum

The pericardium and its contents .

Boundaries of the superior mediastinum

Anteriorly- Manubrim sterni

Posteriorly- Upper four thoracic vertebrae

Superiorly- Plane of the thoracic inlet

Inferiorly- imaginary plan passing through the sternal angle in front, and the lower border body of the fourth thoracic vertebra behind.

On each side- Mediastinal pleura

Contents of the superior mediastinum

Trachea and oesphagus

Muscles

arteries

Veins

Nerves

Thymus

Thoracic duct

Lymph nodes

Muscles of the superior mediastinum

Origins of:

1. sternohyoid

2. sternothyroid

3. lower ends of the Longus colli

Arteries of the superior mediastinum

Arch of aorta

Branchiocephalic artery

Left common carotid artery

Left subclavian artery

Veins of the superior mediastinum

Left and right brachiocephalic veins

upper half of the superior vena cava

Left superior intercostal vein

Nerves of the superior mediastinum

Vagus

Phrenic cardiac nerves of both sides

Left recurrent laryngeal nerve

Lymph nodes of the suprior mediastinum

Paratracheal

Brachicephalic

Tracheobronchial

Boundaries of the anterior mediastinum

Anteriorly→ Body of sternum

Posteriorly→ Pericardium

superiorly- > Imaginary plane

Inferiorly→ Superior surface of the diaphram

on both sides → Mediastinal pleura

Contents of the anterior mediastinum

Sternopericardial ligaments

Lymph nodes with lymphatics

Small mediastinal branches of the internal thoracic artery

lowest part of the thymus

areolar tissue.

Boundaries of the middle mediastinum

anteriorly→ Sternopericardial ligaments

Posteriorly→ Esophagus, descending thoracic aorta and azygous vein

On each side → mediastinal pleuraa

Contents of middle mediastinum

Heart enclosed in pericardium

Arteries

Veins

Nerves

Lymph nodes

Arteries of the middle mediastinum

Ascending aorta

Pulmonary trunk

Two pulmonary arteries

Veins of the middle mediastinum

Lower half of the superior vena cava

Terminal part of the azygos vein

right and left pulmonary veins

Nerves of the middle mediastinum

Phrenic

Deep cardiac plexus

Lymph nodes of the middle mediastinum

Tracheobronchial nodes

Boundaries of the posterior mediastinum

Anteriorly→ Pricardium, bifurcation of trachea, pulmonary vessels and posterior part of the upper surface of the diaphragm.

Posteriorly→ lower eight thoracic vertebrae and intervening discs

on each side→ mediastinal pleura

Contents of the posterior mediastinum

Oesaphagus

arteries → descending aorta

Veins

nerves

Lymph nodes and lymphatics

Thoracis duct.

Veins of the posterior mediastinum

Azygos

Hemiazygos vein

Accessory hemiazygos vein

Nerves of the posterior mediastinum

Vagi

Splanchnic nerves → greate, lesser and least

Lymph nodes and lymphatics of the posterior mediastinum

Posterior mediastinal lymph nodes lying alongside the aorta

Thoracic duct.

Superior mediastinal mass

Most frequently caused by intrathoracic extension of the thyroid gland.

Middle mediastinal mass

Usually results from enlarged lymph nodes