Anatomy of Middle Mediastinum

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Questions and Answers

What is the termination point of the aortic arch?

Lower border of 4th thoracic vertebra, continues as the descending aorta

What structures does the aortic arch pass over?

Hilum of the left lung and bifurcation of the trachea

What is the relation of the aortic arch to the trachea?

Posteriorly, the aortic arch is related to the trachea

What are the branches of the descending thoracic aorta?

Posterior intercostal arteries, subcostal arteries, and pericardial branches Signup and view all the answers

Where does the descending thoracic aorta terminate?

Aortic opening of the diaphragm in the midline Signup and view all the answers

What is the relation of the descending thoracic aorta to the vertebral column?

Posteriorly, the descending thoracic aorta is related to the vertebral column Signup and view all the answers

What forms the anterior border of the pericardium?

Anterior border of pericardium Signup and view all the answers

What are the three parts of the great vessels found in the middle mediastinum?

Ascending aorta, Pulmonary trunk with left and right pulmonary arteries & veins, Inferior half of superior vena cava Signup and view all the answers

What nerves are found in the middle mediastinum?

Phrenic nerve and Deep part of cardiac plexus Signup and view all the answers

What are the boundaries of the posterior mediastinum?

Transverse thoracic plane (superiorly), Posterior 1/3rd diaphragm (inferiorly), Tracheal bifurcation, fibrous pericardium, pulmonary vessels (anteriorly), 4th/5th - 12th thoracic vertebrae (posteriorly), Mediastinal pleura (laterally) Signup and view all the answers

What is found in the aorto-oesophageal recess in the posterior mediastinum?

Azygos and hemiazygos veins Signup and view all the answers

What are the four main structures found in the posterior mediastinum?

Posterior mediastinal lymph nodes & thoracic duct, Descending aorta & its branches, Azygos, hemiazygos, accessory hemiazygos veins, Oesophagus (thoracic part) & vagus nerve & eosophageal nerve plexus Signup and view all the answers

What is the origin of the right subclavian artery and where is it located?

The origin of the right subclavian artery is the brachiocephalic trunk, posterior to the sternoclavicular joint. Signup and view all the answers

What is the course of the left subclavian artery?

The left subclavian artery ascends into the neck, posterior to the scalenus muscle, and then inferolaterally to the external border of the 1st rib to become the left axillary artery. Signup and view all the answers

What is the relationship between the brachiocephalic trunk and the trachea?

The brachiocephalic trunk is anterior to the trachea. Signup and view all the answers

Where does the left common carotid artery pass posterior to?

The left common carotid artery passes posterior to the left sternoclavicular joint. Signup and view all the answers

What is the superior phrenic branch of the aorta responsible for supplying?

The superior phrenic branch of the aorta is responsible for supplying the superior aspect of the diaphragm. Signup and view all the answers

What is the mediastinal branch of the aorta responsible for supplying?

The mediastinal branch of the aorta is responsible for supplying the posterior mediastinum. Signup and view all the answers

What is the length of the thoracic part of the superior vena cava?

7cm Signup and view all the answers

What is the function of the brachiocephalic veins?

Drain blood from the head, neck, and upper limb Signup and view all the answers

What is the direction of the right brachiocephalic vein?

Descend almost vertical, anterolateral to the brachiocephalic trunk Signup and view all the answers

What is the relation of the superior vena cava to the trachea?

Posteromedially Signup and view all the answers

What is the length of the left brachiocephalic vein?

6cm Signup and view all the answers

What is the clinical application of the superior vena cava?

Superior vena cava obstruction Signup and view all the answers

What is the purpose of the fibrous pericardium in relation to disease?

To provide a physical barrier Signup and view all the answers

What is the connection between the inferior part of the fibrous pericardium and the diaphragm?

Continuous with central tendon of diaphragm (pericardiophrenic ligament) Signup and view all the answers

What is the composition of the visceral layer of the serous pericardium?

Mainly ciliated mesothelial cells Signup and view all the answers

What is the significance of the reflection of serous pericardium around great vessels?

Forms pericardial sinuses Signup and view all the answers

What is the function of the pericardium in relation to cardiac stability?

Provides intrathoracic cardiac stability Signup and view all the answers

What is the function of the pericardium in relation to atrial filling?

Facilitates atrial filling Signup and view all the answers

Study Notes

Aortic Arch and Descending Thoracic Aorta

The aortic arch ascends anterior to the right pulmonary artery and bifurcation of the trachea, then passes over the hilum of the left lung and descends posterior to the left T4 vertebra.
Termination: Lower border of the 4th thoracic vertebra, continuing as the descending aorta.

Aortic Arch Relations

Anteriorly: Left lung and pleura, remains of thymus, left superior intercostal vein, left phrenic nerve, and left vagus nerve and its branches.
Posteriorly: Trachea, oesophagus, thoracic duct, and vertebral column.
Superiorly: Brachiocephalic trunk, left common carotid, and left subclavian arteries.
Inferiorly: Bifurcation of pulmonary trunk, left bronchus, ligamentum arteriosum, and left recurrent laryngeal nerve.

Descending Thoracic Aorta

Origin: Continuation from the arch of aorta at the left lower border of the 4th thoracic vertebra.
Course: Descends on the left side of T5 – T12 vertebrae, lying posterior to the root of the left lung, pericardium, and oesophagus.
Termination: Aortic opening of the diaphragm in the midline.

Descending Thoracic Aorta Relations

Anterior: Hilum of the left lung, oesophagus.
Posterior: Vertebral column, accessory hemiazygos, and hemiazygos.
Right: Thoracic duct and azygos vein.
Inferior: Mediastinal pleura of both lungs.

Descending Thoracic Aorta Branches

Posterior intercostal arteries (3rd – 11th post. intercostal arteries on each side).
Subcostal arteries (both sides) – Running along the lower border of the 12th rib.
Pericardial branches:
- Anterior border of pericardium – anteriorly.
- Posterior border of pericardium – posteriorly.
- Mediastinal parietal pleura – laterally.

Middle Mediastinum Content

Heart and pericardium.
Great vessels:
- Ascending aorta.
- Pulmonary trunk with left and right pulmonary arteries and veins.
- Inferior half of superior vena cava.
Nerves:
- Phrenic nerve.
- Deep part of cardiac plexus.
Tracheal bifurcation and main bronchi.
Root of the lungs.
Subcarinal and lower paratracheal (tracheobronchial) lymph nodes.

Posterior Mediastinum

Longest and narrowest inferior mediastinum.
Boundaries:
- Transverse thoracic plane – superiorly.
- Posterior 1/3rd diaphragm – inferiorly.
- Tracheal bifurcation, fibrous pericardium, and pulmonary vessels – anteriorly.
- 4th/5th – 12th thoracic vertebrae – posteriorly.
- Mediastinal pleura – laterally.

Posterior Mediastinum Content

Posterior mediastinal lymph nodes and thoracic duct.
Descending aorta and its branches.
Azygos, hemiazygos, and accessory hemiazygos veins.
Oesophagus (thoracic part).
Vagus nerve and oesophageal nerve plexus.

Clinical Applications

Posterior pericardium.
Oesophageal branches.
Distal thoracic oesophagus.
Bronchial arteries.
Pulmonary areolar tissue and visceral pleura.
Mediastinal branches.
Posterior mediastinum.
Superior phrenic branches – Supplying superior aspect of diaphragm.

Brachiocephalic Trunk

First and largest branch of the aortic arch, 4 – 5 cm length.
Anterior to trachea and posterior to left brachiocephalic vein.
Course: Ascends superolaterally to the right of trachea, dividing into right subclavian and right common carotid arteries behind the right sternoclavicular joint.

Right Common Carotid Artery and Right Subclavian Artery

Origin: Brachiocephalic trunk, posterior to sternoclavicular joint.
Course: Ascends superolaterally to 1st rib (posterior to sternal end of clavicle and scalenus anterior), then inferolaterally across superior 1st rib becoming axillary artery at its external border.

Left Subclavian Artery

Origin: Third branch of the aortic arch, lies posterior to left common carotid artery.
Course: Ascends into neck (post to scalenus muscle), then inferolaterally to external border 1st rib to become left axillary artery.

Left Common Carotid Artery

Origin: Second branch of the aortic arch, lies posterior to and to the left of the brachiocephalic trunk.
Course: Ascends anterior to left subclavian artery to the left of trachea, then passes posterior to left sternoclavicular joint to enter the neck.

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Description

Test your knowledge of the middle mediastinum's contents, including the heart, great vessels, nerves, and other structures. Identify the different components and their locations.