8. Posterior Mediastinum

Question 1

What are the different divisions of the mediastinum?

Answer 1

Superior (above sternal angle)
Inferior (below the sternal angle)
Inferior is divided into anterior, middle and posterior

Question 2

Describe the arrangement of the vagus nerve and phrenic nerve in the mediastinum.

Answer 2

Vagus nerve runs posterior to the airways

Phrenic runs anterior to the airways and is embedded in the pericardium

Question 3

What do the left and right recurrent laryngeal nerves wind around?

Answer 3

Left: Aorta
Right: Right subclavian artery

Question 4

Contents of posterior mediastinum

Answer 4

Oesophagus
Descending aorta
Thoracic duct
Azygos venous system
Posterior mediastinal lymph nodes
Thoracic sympathetic trunks
Splanchnic nerves

Question 5

Where does the oesophagus begin and end?

Answer 5

Pharynx to stomach
Begins C7
Ends T11

Question 6

Where does the oesophagus pass through the diaphragm?

Answer 6

T10

Question 7

Describe the position of the oesophagus above and below T7

Answer 7

Above T7: Right of aorta

Below T7: Left of aorta

Question 8

Where are the 4 constrictions of the oesophagus?

Answer 8

Junction of oesophagus with pharynx
Where oesophagus is crossed by arch of aorta
Where oesophagus is compressed by left main bronchus
At the oesophageal hiatus (where oesophagus passes through diaphragm to abdominal cavity)

Question 9

Describe the position and orientation of the azygous vein.

Answer 9

Runs along the right side of the vertebral bodies and arches anteriorly over the right main bronchus to join the SVC.

Question 10

Arteries to the oesophagus

Answer 10

Branch of the aorta directly as adjacent to oesophagus

Question 11

Intercostal arteries

Answer 11

Posterior: Emerge from aorta
Anterior: Emerge from thoracic vessels

Question 12

What differs about the posterior blood supply to intercostal spaces 1 and 2? Why?

Answer 12

Aorta doesn’t extend that high
Posterior intercostal going to spaces 1 and 2 receive their supply from above (left and right subclavian arteries- which give rise to supreme intercostal artery)

Question 13

Describe the azygos venous system.

Answer 13

Azygos vein runs along the right side of the vertebral bodies and drains the right side of the chest wall. Accessory hemiazygos (superior to the hemiazygos) and the hemiazygos drain the left side of the chest wall and drain into the azygos.
Azygos then arches anteriorly over the lung root and joins the SVC just above right atrium

Question 14

What is the purpose of the azygous venous system

Answer 14

Drains posterior wall of chest, upper abdomen and posterior mediastinal organs

Question 15

Describe the relations of the azygos vein.

Answer 15

Azygos vein arches anteriorly over right lung root to join the superior vena cava.

Question 16

Describe the arrangement of the vagus nerve and phrenic nerve in the inferior mediastinum.

Answer 16

Vagus nerve runs posterior to the airways and forms plexus following oesophagus into abdomen
Phrenic runs anterior to the airways and crosses pericardium to diaphragm

Question 17

What are the main branches of the vagus nerve?

Answer 17

Parasympathetic: to heart and lungs (control of smooth and cardiac muscle + glands of gut and airways)
Large sensory fibres from gut and lungs
Recurrent laryngeal nerve (voluntary) is NOT parasympathetic: it runs up the neck to supply most skeletal muscles of the larynx

Question 18

What structure does the right vagus nerve lie on?

Answer 18

Trachea

Question 19

Describe the relations of the vagus nerves to the great arteries.

Answer 19

Run lateral to the 2 common carotid arteries.

Question 20

Describe the paths of the left vagus and left phrenic nerves.

Answer 20

Left vagus crosses anteriorly to the aortic arch and behind lung root
Left phrenic nerve crosses more anteriorly in front of the aortic arch.

Question 21

What structures do the phrenic nerves provide sensory and motor innervation to?

Answer 21

Motor: diaphragm
Sensory: 
central tendon of diaphragm
mediastinal pleura
pericardium
peritoneum of central diaphragm

Question 22

What vertebral level do the phrenic nerves emerge from?

Answer 22

C3, 4 and 5

Question 23

Where does the vagus nerve go through the diaphragm?

Answer 23

T10

Question 24

What is the nerve that branches off the vagus in the mediastinum near the left lung?

Answer 24

Left recurrent laryngeal nerve

Question 25

Describe the path of the right phrenic nerve to reach the diaphragm.

Answer 25

Right phrenic nerve passes along the right brachiocephalic vein, along the SVC, and along the right side of the heart and pericardium to the diaphragm.

Question 26

Describe the path of the left recurrent laryngeal nerve.

Answer 26

The left recurrent laryngeal nerve is a branch of the left vagus nerve, which arches around the ligamentum arteriosum and moves up towards the larynx.

Question 27

Describe the path of the right recurrent laryngeal nerve.

Answer 27

The right recurrent laryngeal nerve branches off the right vagus nerve more superiorly and loops around the right subclavian artery.

Question 28

Which positions do the right and left vagus nerves occupy?

Answer 28

Left: Occupies position on front, becomes Anterior vagal trunk
Right: Occupies position on back, becomes Posterior vagal trunk

Question 29

Which spinal nerves do the sympathetic trunk receive branches from?

Answer 29

T1-L2

Question 30

What is the role of sympathetic trunks?

Answer 30

Distribute sympathetic nerves to smooth muscle and glands throughout body

Question 31

Where do the nerves to the body wall synapse?

Answer 31

In ganglia of sympathetic trunks

Question 32

Where do the nerves to the internal organs synapse?

Answer 32

In local ganglia

Question 33

What do sympathetic trunks bring?

Answer 33

Pain fibres back to CNS from viscera

Question 34

What are the fibres in the lower sympathetic trunk called and which vertebral levels do they branch off at?

Answer 34

Splanchnic Nerves

T5-T12

Question 35

What vertebral levels do the IVC, oesophagus and aorta go through the diaphragm?

Answer 35

8, 10, 12