The Mediastinum Flashcards
What 4 structures does the mediastinum extend to?
Thoracic inlet/aperture
Diaphragm
Sternum and costal cartilages
Thoracic vertebrae
What features of the mediastinum make it highly mobile in living people?
Contains hollow, air or fluid-filled structures
Allows for movement of the lungs, heart, great vessels and oesophagus
What splits the mediastinum into its superior and inferior parts? What vertebral level is this at?
Transthoracic plane (manubriosternal joint/sternal angle) T4/5
What is the position of the aortic arch, tracheal bifurcation and central tendon when a person is in the supine position?
Aortic arch lies superior to transthoracic plane
Tracheal bifurcation transected to transthoracic plane
Central tendon lies at level of xiphisternal junction and T9
What is the position of the aortic arch, tracheal bifurcation and central tendon when a person is standing?
Arch of aorta transected by transverse thoracic plane
Tracheal bifurcation lies inferior to transthoracic plane
Central tendon may fall to middle of xiphoid process T9-10 IV disc
What is contained in the superior mediastinum?
Brachiocephalic veins and superior vena cava Great vessels Ascending and arch of aorta Trachea Oesophagus Thymus gland
What is contained in the inferior mediastinum?
Heart
Oesophagus
Descending aorta
Inferior vena cava
Which nerves run through the superior mediastinum?
Phrenic nerve (C3, 4 ,5 - innervation to diaphragm) Vagus nerve and recurrent laryngeal nerves
Which vessels/ducts are located in the superior mediastinum?
Brachiocephalic vein and superior vena cava
Arch of aorta and great vessels
Thoracic ducts and lymphatic trunks
What cranial nerve is the vagus nerve and what does it provide innervation to?
CN X - cranial nerve 10
Innervation to oesophagus, heart and bronchi
Recurrent laryngeal loops back to innervate larynx (right – under right subclavian artery,
left – under arch of aorta)
What vertebral level is the phrenic nerve at and what does it innervate?
C3-5
Motor to diaphragm
Sensory to pericardium, mediastinal pleura
Why and how often does phrenic nerve paralysis occur? What does it cause and how is it confirmed?
Rare (approx 8%) complication following chest surgery - mostly transient
Results in elevation of ipsilateral hemidiaphragm
Post-operative radiograph confirms
What vertebral level is the trachea at? What are some of its features?
C6-T4
Cartilaginous rings U shaped
Carina (bifurcation into primary bronchi) at transthoracic plane T4/5
Aorta arches over left main bronchus and lung root
What vertebral level is the oesophagus at? What are some of its features?
C6-10
Immediately posterior to trachea
Inclines to the left but compressed by the aortic arch (T4) and the root of the left lung (left main bronchus T5-T6)
What is the contents of the inferior mediastinum?
Anterior mediastinum o Thymus Middle mediastinum o Pericardium and heart Posterior mediastinum o Primary bronchi o Oesophagus (& oesophageal plexus) o Descending aorta o Thoracic duct o Azygos and hemi azygos veins
What are the features of the pericardium?
Tough outer fibrous pericardium stabilizes the heart
o Prevents over-dilation
Serous pericardium (the collapsed sac)
o Parietal pericardium
o Visceral pericardium
As heart grows into the serous sac is fills pericardial cavity
o Leaves potential space between layers of serous pericardium
What is the arterial supply to the posterior thoracic wall?
Posterior intercostal arteries are branches of descending aorta
Except 1 and 2, which branch from costocervical trunk which comes off the subclavian arteries
Where are the anterior intercostal arteries supplied from?
From internal thoracic artery which runs deep to costal cartilages
Internal thoracic artery from subclavian arteries
Where are the anterior intercostal arteries located?
Run in upper part of each intercostal space (with their corresponding nerve and vein in neurovascular bundle) in then costal groove
Smaller collateral branch in inferior part of the intercostal space
What do the anterior intercostal arteries anastomose with in each space?
Posterior intercostal arteries
What is the azygos system and what does it contain?
Thoracic venous drainage Veins more variations Anterior intercostal veins o Internal thoracic vein Posterior intercostal veins o Azygos vein – right o Hemiazygos veins – left
