Lecture 4: Posterior mediastinum

Question 1

What are the boundaries of the posterior mediastinum?

Answer 1

Anterior - posterior pericardium
Posterior - vertebrae T5-12
Lateral - mediastinal pleura 
Superior - transverse thoracic plane
Inferior - diaphragm

Question 2

What is the contents of the posterior mediastinum?

Answer 2

Oesophagus
Thoracic aorta
Azygos system of veins
Thoracic duct
Vagus nerve
Sympathetic trunk
Splanchnic nerves

Question 3

What is the sympathetic trunk?

Answer 3

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

Question 4

Describe the upper 5 ganglia in the sympathetic trunk.

Answer 4

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

Question 5

What is a dermatome?

Answer 5

An area of skin supplied by a single spinal cord level or spinal nerve

Question 6

Describe the lower 7 ganglia in the sympathetic trunk.

Answer 6

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

Question 7

Which levels form the greater splanchnic nerves?

Answer 7

T5-T9

Question 8

Which levels form the lesser splanchnic nerves?

Answer 8

T10-T11

Question 9

Which levels form the least splanchnic nerves?

Answer 9

T12

Question 10

What types of fibres are carried in the splanchnic nerves?

Answer 10

Preganglionic sympathetic fibers to the abdominal viscera

Visceral afferent fibers from the abdominal viscera

Question 11

Where does the vagus nerve originate?

Answer 11

CNX

Question 12

Where do the vagus nerves enter the superior mediastinum?

Answer 12

Posterior to the sternoclavicular joint

Question 13

Which plexi do the vagus nerves contribute to?

Answer 13

Pulmonary, cardiac and oesophageal plexi

Question 14

What type of supply is carried by the vagus nerve?

Answer 14

Parasympathetic

Question 15

Where does the right recurrent laryngeal nerve travel?

Answer 15

Hooks under right subclavian artery and ascends between trachea and oesophagus

Question 16

Where does the right vagus nerve travel?

Answer 16

Continues posterior to the right of the trachea, posterior to right brachiocephalic vein and lung root

Question 17

Where does the left recurrent laryngeal nerve travel?

Answer 17

Hooks inferiorly to the aortic arch, immediately lateral to ligamentum arteriosum

Question 18

Where does the left vagus nerve travel?

Answer 18

Runs posteriorly to lung root

Question 19

Which side of the vertebral column is the thoracic aorta?

Answer 19

Left

Question 20

At what vertebral levels is the descending aorta?

Answer 20

T5-T12

Question 21

Where is the oesophagus in relation to the thoracic aorta?

Answer 21

To its right

Question 22

At what level does the aorta enter the abdomen?

Answer 22

T12

Question 23

Where are the thoracic duct and azygos vein in relation to the thoracic aorta?

Answer 23

On its right side

Question 24

What are the branches of the thoracic aorta?

Answer 24

Bronchial (paired)
Posterior intercostal
Subcostal
Pericardial
Oesophageal 
Superior Phrenic

Question 25

Which vessels drain into the azygos vein?

Answer 25

Posterior intercostal veins Bronchial veins Vertebral venous plexus

Question 26

Which levels of intercostal veins drain into the hemi-azygos vein?

Answer 26

Left side T9-T11

Question 27

Which levels of intercostal veins drain into the accessory hemi-azygos vein?

Answer 27

Left side T5-T8

Question 28

At what vertebral level does the (accessory) hemi-azygos cross to meet the azygos?

Answer 28

T7/T8

Question 29

What is the thoracic duct?

Answer 29

Largest lymph channel Conveys all lymph from body except the head, neck, upper limb and thorax on the right side

Question 30

Where does the thoracic duct originate?

Answer 30

At the cisterna chyli

Question 31

At what vertebral level is the cisterns chyli?

Answer 31

L2

Question 32

Where in the diaphragm does the thoracic duct pass through?

Answer 32

Aortic hiatus

Question 33

Where does the thoracic duct drain into?

Answer 33

Left venous angle (junction internal jugular and subclavian junction)

Question 34

Which region of the heart is just anterior to the oesophagus?

Answer 34

The left atrium

Question 35

At what level does the oesophagus pierce the diaphragm?

Answer 35

T10

Question 36

At what level does the oesophagus enter the stomach?

Answer 36

T11

Question 37

What are the three constrictions of the oesophagus?

Answer 37

Arch of aorta Left main bronchus Diaphragm

Question 38

What innervates the oesophagus?

Answer 38

CNX and sympathetic trunk via the oesophageal plexus

Question 39

Which structures transcend from the superior mediastinum to the posterior mediastinum?

Answer 39

``` Oesophagus Thoracic duct Vagus nerve Phrenic nerve Aorta ```