Lecture 4: Posterior mediastinum Flashcards
What are the boundaries of the posterior mediastinum?
Anterior - posterior pericardium Posterior - vertebrae T5-12 Lateral - mediastinal pleura Superior - transverse thoracic plane Inferior - diaphragm
What is the contents of the posterior mediastinum?
Oesophagus Thoracic aorta Azygos system of veins Thoracic duct Vagus nerve Sympathetic trunk Splanchnic nerves
What is the sympathetic trunk?
Vertical chain of sympathetic nerves running the entire length of the vertebral column
Located on both sides of vertebral bodies
Paravertebral ganglia located along its length
In the thoracic spine usually one ganglion per spinal level
Describe the upper 5 ganglia in the sympathetic trunk.
Preganglionic sympathetic fibers leave the spinal cord (white rami communicantes) and synapse at the ganglion
Postganglionic sympathetic fibers leave the ganglion (grey rami communicantes) and pass to the pulmonary, cardiac & oesophageal plexi
These also carry afferent fibers (carrying sensory information) from the thoracic viscera they supply back to the brain
What is a dermatome?
An area of skin supplied by a single spinal cord level or spinal nerve
Describe the lower 7 ganglia in the sympathetic trunk.
Preganglionic sympathetic fibers leave the spinal cord (white rami communicantes) and enter the ganglion but don’t synapse
Hence, Preganglionic sympathetic fibers leave these ganglia and pass to the abdominal viscera
These form the 3 Splanchnic nerves
Which levels form the greater splanchnic nerves?
T5-T9
Which levels form the lesser splanchnic nerves?
T10-T11
Which levels form the least splanchnic nerves?
T12
What types of fibres are carried in the splanchnic nerves?
Preganglionic sympathetic fibers to the abdominal viscera
Visceral afferent fibers from the abdominal viscera
Where does the vagus nerve originate?
CNX
Where do the vagus nerves enter the superior mediastinum?
Posterior to the sternoclavicular joint
Which plexi do the vagus nerves contribute to?
Pulmonary, cardiac and oesophageal plexi
What type of supply is carried by the vagus nerve?
Parasympathetic
Where does the right recurrent laryngeal nerve travel?
Hooks under right subclavian artery and ascends between trachea and oesophagus
Where does the right vagus nerve travel?
Continues posterior to the right of the trachea, posterior to right brachiocephalic vein and lung root
Where does the left recurrent laryngeal nerve travel?
Hooks inferiorly to the aortic arch, immediately lateral to ligamentum arteriosum
Where does the left vagus nerve travel?
Runs posteriorly to lung root
Which side of the vertebral column is the thoracic aorta?
Left
At what vertebral levels is the descending aorta?
T5-T12
Where is the oesophagus in relation to the thoracic aorta?
To its right
At what level does the aorta enter the abdomen?
T12
Where are the thoracic duct and azygos vein in relation to the thoracic aorta?
On its right side
What are the branches of the thoracic aorta?
Bronchial (paired) Posterior intercostal Subcostal Pericardial Oesophageal Superior Phrenic
Which vessels drain into the azygos vein?
Posterior intercostal veins
Bronchial veins
Vertebral venous plexus
Which levels of intercostal veins drain into the hemi-azygos vein?
Left side T9-T11
Which levels of intercostal veins drain into the accessory hemi-azygos vein?
Left side T5-T8
At what vertebral level does the (accessory) hemi-azygos cross to meet the azygos?
T7/T8
What is the thoracic duct?
Largest lymph channel
Conveys all lymph from body except the head, neck, upper limb and thorax on the right side
Where does the thoracic duct originate?
At the cisterna chyli
At what vertebral level is the cisterns chyli?
L2
Where in the diaphragm does the thoracic duct pass through?
Aortic hiatus
Where does the thoracic duct drain into?
Left venous angle (junction internal jugular and subclavian junction)
Which region of the heart is just anterior to the oesophagus?
The left atrium
At what level does the oesophagus pierce the diaphragm?
T10
At what level does the oesophagus enter the stomach?
T11
What are the three constrictions of the oesophagus?
Arch of aorta
Left main bronchus
Diaphragm
What innervates the oesophagus?
CNX and sympathetic trunk via the oesophageal plexus
Which structures transcend from the superior mediastinum to the posterior mediastinum?
Oesophagus Thoracic duct Vagus nerve Phrenic nerve Aorta
