Mediastinum Flashcards
What is the mediastinum?
Central compartment of the thorax between the pleural cavities
Where is the transverse thoracic plane?
Sternal angle/manubriosternal joint anteriorly
T4/T5 posteriorly
What divides the inferior mediastinum into anterior, middle and posterior?
Pericardial sac
Where is the anterior inferior mediastinum?
Under transverse thoracic plane
Behind sternum
In front of pericardium
Where is the posterior inferior mediastinum?
Under transverse thoracic plane
Behind pericardium
In front of vertebrae T5 to T12
What is contained in the superior mediastinum? (9)
Aortic arch
Brachiocephalic veins –> upper half of superior vena cava
Sympathetic chain
Vagus and phrenic nerves
Trachea
Oesophagus
Thoracic duct
Thymus (remnant)
Lymph nodes
What are the three branches of the aortic arch?
Brachiocephalic trunk
Left common carotid
Left subclavian
Which veins come together to form the brachiocephalic veins?
Internal jugular vein
Subclavian vein
Where does the sympathetic nervous system originate?
T1-L2
What cranial nerve is the vagus nerve?
CNX
Where in the superior mediastinum are the brachiocephalic veins?
Anterior
Where does the vagus nerve run?
Carotid sheath - vagus, common carotid, internal jugular
Behind root of lung
More medially than phrenic
Where and what is the cardiac plexus?
Arch of aorta
Autonomic innervation to heart
What is the path of the left recurrent laryngeal nerve?
Branches off vagus
Swoops beneath aorta and back up to larynx
Where does the phrenic nerve originate?
C3, 4, 5
What does the phrenic nerve innervate?
Diaphragm
What happens to the trachea at the transverse thoracic plane?
Bifocates into bronchi
What hugs the oesophagus?
Vagus nerves
What is the thoracic duct?
Largest lymphatic vessel in the body
Where does the vagus nerve originate?
Brainstem
What is contained in the anterior inferior mediastinum?
Thymus (remnant)
What is contained in the middle inferior mediastinum?
Pericardium and heart
What is contained in the posterior inferior mediastinum?
Descending aorta
Primary bronchi
Oesophagus
Azygos vein system
Thoracic duct
What structures are anterior in the posterior inferior mediastinum?
Descending aorta
Primary bronchi
Oesophagus
What structures are posterior in the posterior inferior mediastinum?
Azygos vein system
Thoracic duct
On what side of the vertebral column is the descending aorta?
Left
At what level does the inferior vena cava pass through the diaphragm?
T8
At what level does the oesophagus pass through the diaphragm?
T10 (muscular component)
At what level does the descending aorta pass through the diaphragm?
T12
What are the branches of the descending aorta?
Posterior intercostal arteries from T3 downwards
Left bronchial artery
What does the right bronchial artery branch off?
Third posterior intercostal artery
What does the brachiocephalic trunk branch into?
Right common carotid
Right subclavian
What branches from the right subclavian artery?
- Right internal thoracic artery
Branches into anterior intercostals and pericardiophrenic artery
- Costocervical trunk
Where does the right internal thoracic artery run?
Directly behind sternum
What does the pericardiophrenic artery supply?
Pericardium
Diaphragm
What does the costocervical trunk supply?
Branches for T1 and T2 intercostals
Where does the oesophagus pass through the diaphragm in relation to the aorta?
Antero-superiorly
What do the right posterior intercostal veins drain into?
Azygos vein
What side of the vertebral bodies does the azygos vein run?
Right
What do the left posterior intercostal veins drain into?
Accessory hemiazygos vein
Hemiazygos vein
What side of the vertebral bodies do the accessory hemiazygos and hemiazygos veins run?
Left
Where does the azygos vein drain?
Upward and over the root of the right lung into the superior vena cava
What do the accessory hemiazygos and hemiazygos veins drain into?
Azygos vein (branch across vertebral column)
What do the anterior intercostal veins drain into?
Internal thoracic vein
What does the internal thoracic vein drain into?
Subclavian vein
What does the thoracic duct do?
Collects lymph from lower limbs and intestines
What is the cysterna chyli?
Dilated sac at lower end of thoracic duct
All fluid from below diaphragm passes through
What is the path of the thoracic duct?
Runs superiorly between oesophagus and descending aorta
Crosses right to left at T4/T5 lying between azygos vein and aorta
Where does the thoracic duct drain?
Venous system where left internal jugular and left subclavian meet
What drains the tissue fluid of the right arm, head and neck?
Right lymphatic duct
Where does the right lymphatic duct drain?
Venous system where right internal jugular and right subclavian meet
From which rami do the intercostal nerves originate?
Anterior
Which rami leads to the sympathetic chain?
White
Which rami leads away from the sympathetic chain?
Grey
What protects the intercostal nerves?
Intercostal groove
Where is the lateral horn?
T1-L2
Grey matter of spinal cord
(Intermediolateral column)
What does the sympathetic chain contain?
POSTganglionic sympathetic cell bodies
Where are sympathetic preganglionic cell bodies located?
Lateral horn
What is the function of sympathetic stimulation in the lungs?
Bronchodilation
Vasoconstriction
What is the function of the sympathetic stimulation in the heart?
Increase heart rate
Increase contractility
