The Mediastinum Flashcards
What is the mediastinum?
Middle compartment of the thoracic cavity.
What is the extent of the mediastinum? (5)
o superior- superior thoracic aperture
o inferior- diaphragm
o anterior- sternum
o posterior- thoracic vertebrae
o lateral- lungs and pleura
What is the superior border of the superior mediastinum?
superior thoracic aperture
What is the inferior border of the superior mediastinum?
level of T4
What is the Anterior border of the superior mediastinum?
manubrium
What is the posterior border of the superior mediastinum?
T1-T4 vertebrae
What is the lateral border of the superior mediastinum?
Lungs and pleurae
What are the contents of the superior mediastinum? (7) (NB: TVATONT)
Thymus gland (remnant)
Veins (brachiocephalic vv. and SVC)
Arteries (pulmonary trunk and branches, arch of aorta and branches)
Trachea (vagus nerve just posterior)
Oesophagus
Nerves (cardiac plexus and left laryngeal nerve)
Thoracic duct and lymphatics
What are the subdivisions of the inferior mediastinum?
Anterior, Posterior and Middle subdivisions.
What is the superior border of the anterior subdivision of the inferior mediastinum?
Level of T4
What is the inferior border of the anterior subdivision of the inferior mediastinum?
Diaphragm
What is the anterior border of the anterior subdivision of the inferior mediastinum?
Body of sternum and xiphoid process
What is the posterior border of the anterior subdivision of the inferior mediastinum?
Pericardium
What is the lateral border of the anterior subdivision of the inferior mediastinum?
Lungs and pleurae
What are the contents of the anterior subdivision of the inferior mediastinum?
Remnant of thymus gland
What are the contents of the anterior subdivision of the inferior mediastinum?
Remnant of the thymus gland
What is the superior border of the posterior subdivision of the inferior mediastinum?
Level of T4
What is the inferior border of the posterior subdivision of the inferior mediastinum?
Diaphragm
What is the anterior border of the posterior subdivision of the inferior mediastinum?
Pericardium
What is the posterior border of the posterior subdivision of the inferior mediastinum?
T5-T12 vertebrae
What is the lateral border of the posterior subdivision of the inferior mediastinum?
Lungs and pleurae
What are the contents of the inferior mediastinum? (7)
Oesophagus
Vagus nerve
Thoracic duct
Azygos vein
Descending aorta
Sympathetic trunks (right and left)
Lymph nodes
What are the boundaries of the middle subdivision of the inferior mediastinum? (4)
- Space enclosed by the pericardium
- Between the mediastinal pleurae
- Lies in the inferior mediastinum
- Largest division of the inferior mediastinum
What are the contents of the middle subdivision of the inferior mediastinum? (4)
- Pericardium and heart
- Great vessels (ascending aorta, SVC, pulmonary trunk)
- Cardiac plexus
- Phrenic nerve and pericardiophrenic vessels
What are the contents of the right side of the mediastinum? (10)
- Right vagus nerve
- Azygos vein and its arch
- SVC
- Phrenic n. and pericardiophrenic arteries
- IVC
- Trachea
- Sympathetic trunk
- Oesophagus
- Pericardium
- Root of lung
What are the contents of the left side of the mediastinum? (10)
- Left subclavian artery
- Left vagus nerve and left recurrent laryngeal nerve
- greater splanchnic nerve
- Phrenic n. and pericardiophrenic arteries
- Thoracic duct
- Aortic arch and thoracic aorta
- Sympathetic trunk
- Oesophagus
- Pericardium
- Root of lung
What are the important structures of the mediastinum? (6)
- Thoracic duct
- Trachea
- Phrenic nerves
- Right vagus nerve
- Left vagus nerve
- Thoracic oesophagus
What is the origin of the thoracic duct?
Origin- chyle cistern in the abdomen
What is the course of the thoracic duct? (6)
o ascends through aortic hiatus in the diaphragm at T12
o ascends in the posterior mediastinum between the oesophagus and azygos vein
o At T4 it crosses to the left
o Ascends to superior mediastinum
o Arches laterally and then inferiorly, anterior to subclavian artery
o Enters at the union of left internal jugular and subclavian veins
What is the blood supply of the trachea? (2)
o Inferior thyroid a.
o Bronchial aa.
What is the venous drainage of the trachea?
o Inferior thyroid venous plexus
What is the innervation of the trachea? (3)
o vagus nn.
o recurrent laryngeal nn.
o sympathetic trunks
What is the origin of the phrenic nerves?
Origin- descends over scalenus anterior to enter the thorax
What are the phrenic nerves accompanied by?
o Accompanied by pericardiophrenic vessels
The phrenic nerve pass anterior to lung roots between ________ pleura and _______.
pleura
pericardium
What do the sensory fibres of the phrenic nerves supply?
Sensory fibers supply pleurae, pericardium and diaphragm
What do the motor fibres of the phrenic nerves supply?
Motor fibers supply diaphragm
What does the Right vagus nerve give rise to?
o Gives rise to right recurrent laryngeal nerve
What does the right vagus nerve run parallel to?
o Runs parallel to right side of trachea
What is the course of the right vagus nerve?
o Passes posterior to right brachiocephalic vein, SVC and root of right lung
What are the features of the Left vagus nerve? (2)
o Loops around arch of aorta
o Gives rise to left recurrent laryngeal nerve
Where does the Thoracic oesophagus enter?
o Enters superior mediastinum at level of T1
What are the features of the superior mediastinum in the Thoracic oesophagus? (3)
o Posteriorly- T1-T4
o On the left- aortic arch, thoracic duct, left rec. laryngeal n., left common carotid a.
o On the right- right rec. laryngeal n. and right vagus n.
What are the features of the inferior mediastinum in the Thoracic oesophagus? (4)
o Posteriorly- T5-T10, thoracic duct, branches of hemiazygos vein
o Anteriorly- pericardium
o On the left- thoracic aorta
o On the right- azygos vein
What is the Thoracic oesophagus constricted by? (3)
o Aortic arch on the left
o Left main bronchus anteriorly
o Oesophageal hiatus
What is the innervation of the Thoracic oesophagus? (3)
o Oesophageal plexus
o Vagus nn.
o Sympathetic trunk
What are the major openings of the diaphragm? (3)
- Caval hiatus
- Oesophageal hiatus
- Aortic hiatus
Caval hiatus
Level:
Contents:
T8
IVC
Terminal branches of right phrenic n.
Oesophageal hiatus
Level:
Contents:
T10
Oesophagus
Right and left vagus nn.
Aortic hiatus
Level:
Contents:
T12
Descending aorta
Thoracic duct