Superior and Posterior Mediastinum Flashcards
Boundaries of the medistinum
Central part of the thorax
Transverse thoracic plane is important
Superior medistinum boundaries
What does not follow vate?
Phrenic/vagus nerve and thoracic duct
Where is the transverse thoracic plane?
Superior mediastinum - orange
Inferior mediastinum - purple
Contents of the superior mediastinum
Thymus
VATE
Veins
Arteries
Trachea
Esophagus
Thoracic Duct
Phrenic Nerves
Vagus Nerves (CN X)
What is an enlarged thymus?
Thymoma - linked with myasthenia gravis
Thymic sail - normal finding on infant radiograph
Right and left brachiocephalic veins (joining into the superior vena cava)
The right is shorter than the left
Right and left internal carotid veins (descend to form the right and left brachiocephalic veins)
Right and left subclavian veins
Where is a preffered access point for a central line?
Right internal jugular vein
Where is the azygus vein located?
What is the innominate artery?
Synonymous with the brachiocephalic artery
Gives rise to the right subclavian and the right common carotid
Where does the bottom of the arch of the aorta end in respect to anatomical landmarks?
The transthoracic plane
Subclavian Steal
Occlusion of the proximal subclavian artery can cause reversal of flow
The subclavian and vertebral aretery are connected through the circle of Willis, which is what causes reversal of flow
Why are inhaled foreign bodies more likely to enlodge in the right main bronchus?
Right main bronchus is larger in diameter and has less of an ascending angle
Why does the cartilage of the trachea not fully circumscribe?
Because the posterior trachea abuts the anterior esophagus. C-shaped cartilaginous rings allow for passage of a food bolus
What is the trachea innervated by?
Vagus that forms the pulmonary plexus
The tracheoesophageal septum dividing the two structures
What is the most posterior structure in the superior mediastinum?
The thoracic duct
Crosses from right to left at the transthoracic plane (TV4-5)
Where are the phrenic nerves derived from?
The cervical plexus (C3-C5)
Interscalene Block
Blocks the cervical plexus, blocking sensation to the upper extremities (exept for a portion of the inner upper arm supplied by the intercostal brachial nerve)
The phrenic nerve can be blocked accidentally, leading to partial temporary or permeanent paralyzation of the diaphragm
Vagus nerves (CN X)
Recurrent laryngeal nerves
R - loops around the right subclavian artery
L - loops around the aorta at the level of the ligamentum arteriosum
Branching from the vagus
Vagus nerve
posterior to the phrenic nerve
adjacent to the trachea
Posterior to the root of the lung
Posterior to the SVC
Start with a mediolateral orientation before taking an anterior/posterior orientation
Boundaries of the posterior mediastinum
Where does the esophagus pass through the diagragm?
TV 10
Where does the aorta exit the diaphragm?
TV 12
Structures of the posterior mediastinum
DATES
Descending aorta
Azygos vein
Thoracic duct
Esophagus
Sympathetics
Coarctation of the aorta
Restriction of flow beyond the aortic arch
Azygos system of veins
What is the largest lympactic vessel?
The thoracic duct
Drains the entire left and lower right extrimity
What happens when the thoracic duct is injured?
Chylothorax
Greater and lesser splachnic nerve locations
Greater - off of T5-T9 (targest foregut derived structures)
Lesser - off of T10-T11 (targets midgut structures)
Least - supplies kidneys and medulla
1 - trachea
2 - superior vena cava
3 - right atrium
4 - aortic arch (knob)
5 - left ventricle
