T1 L11: Posterior mediastinum

• Posterior mediastinum boundaries

  Anterior: posterior pericardium

  Posterior: T5-T12 vertebral bodies

  Lateral: mediastinal pleura

  Superior: transverse thoracic plane

  Inferior: diaphragm

  
• Contents of the posterior mediastinum

  Organs: oesophagus

  arteries: descending aorta, posterior intercostal arteries

  veins: azygos system, posterior intercostal veins

  lymphatics: thoracic duct

  nerves: vagus nerve (CN X), sympathetic trunk, splanchnic nerves
• Autonomic supply to the thorax

  Sympathetic supply: T1 - T5

  Parasympathetic supply: Vagus nerve (arise from brainstem)
• The sympathetic chain

  Spinal nerves are able to travel up or down the chain to reach different vertebral levels. They synapse once they reach the desired vertebral level.

  
• Splanchnic nerves

  Carry preganglionic sympathetic fibres to abdominal viscera.

  Also carry visceral afferent fibres from abdominal viscera.

  Great splanchnic nerve: T5 -9

  Lesser splanchnic nerve: T10-11

  Least splanchnic nerve: T12

  
• Referred pain

  pain felt in a location different from the cause

  Dermatome: area of skin innervated by a specific spinal cord segment

  eg visceral afferent nerves return to spinal cord following sympathetic nerve, joined by somatic sensory nerves of T1-4 dermatome. Brian is unable to make a distinction between locations.

  
• Vagus Nerve

  Cranial nerve 10 (CN X)

  Pass posterior to main bronchi

  Provides parasympathetic supply via pulmonary, cardiac and oesophageal plexuses.

  Recurrent laryngeal branches travel superiorly to provide motor supply to the larynx.

  
• Recurrent Laryngeal Nerves

  Innervation to majority of laryngeal muscles

  Right Recurrent Laryngeal Nerve: loops under subclavian artery

  Left Recurrent Laryngeal Nerve: loops under aortic arch

  
• Parts of aorta and their locations

  Ascending: Middle mediastinum

  Arch: Superior mediastinum

  Descending: Posterior mediastinum

  
• Branches of the descending (thoracic) aorta

  Paired branches:

  • posterior intercostal
  • subcostal
  • superior phrenic

  Unpaired branches:

  • bronchial
  • mediastinal (pericardial)
  • oesophageal

  
• Azygos system

  Veins of the thoracic wall drain into the azygos vein

  Azygos vein drains into the superior vena cava

  Called 'azygos' because not a paired system

  
• Azygos vein

  Formed by the union of:

  • right subcostal vein
  • right ascending lumbar vein

  Trubutaries:

  • right posterior intercostal veins (T5-T11)
  • Hemiazygos vein
  • Accessory hemiazygos vein
  • Right superior intercostal vein

  Passes through aortic hiatus of the diaphragm

  Arches over the root of the right lung

  Drains into posterior aspect of superior vena cava

  
• Hemiazygos vein:

  Formed by left subcostal vein and left ascending lumbar vein

  Drains the left posterior intercostal veins (T9-T11)

  
• Accessory Hemiazygos vein

  Drains the left posterior intercostal veins (levels T4-T8)

  
• Thoracic duct


  Largest lymph channel in the body

  Originates from Cisterna Chyli in abdomen L2

  Ascends through aortic hiatus

  Drains into venous system at the left venous angle
• Oesophagus


  Runs right to the aorta in posterior mediastinum before moving left

  Travels though diaphragmatic hiatus at T10

  Innervated by vagus nerve CNX and sympathetic nerves from the sympathetic chain via oesophageal plexus

  Three constriction points along its course:

  • Arch of aorta
  • left main bronchus
  • diaphragm

  
• What is the route of the azygos vein?

  pass through aortic hiatus of diaphragm → arch over root of right lung → drain into posterior superior vena cava

  
• How does the hemiazygos vein go?

  left subcostal vein + left ascending lumbar vein → hemiazygos vein → posterior intercostal veins

  
• What does the accessory hemiazygos vein drain into?


  left posterior intercostal veins

  
• From where does the thoracic duct drain lymphatic fluid from?


  all portions of body except:

  • right head and neck
  • right thorax
  • right limb

  
• What are the 3 constrictions of the oesophagus?

  arch of aorta

  left main bronchus

  diaphragm (oesophageal hiatus)

  most common sites for foreign body to become lodged or food impaction

  
• What vertebral body does the inferior vena cava pass through the diaphragm?

  T8
• What vertebral level does the aorta pass through the diaphragm?

  T12
• What vertebral level does the oesophagus pass through the diaphragm?

  T10