1.3 - The Mediastinum

Question 1

What are the main contents of the mediastinum?

Answer 1

Trachea, Oesophagus, Aorta, Superior Vena Cava, Heart, pericardium, thoracic duct, nerves

Question 2

What are the different divisions of the mediastinum?

Answer 2

Superior (above sternal angle), Inferior (below the sternal angle)

Inferior is divided into anterior, middle and posterior

Question 3

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

Answer 3

Vagus nerve runs posterior to the airways

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

Question 4

What vertebral level do the phrenic nerves emerge from?

Answer 4

C3, C4, C5

Question 5

What is the name of the connection between the pulmonary artery and the aorta? What is this a remnant of?

Answer 5

Ligamentum Arteriosum - remnant of the ductus arteriosus

Question 6

Where does the vagus nerve go through the diaphragm?

Answer 6

T10 - along with the oesophagus

Question 7

Describe the position and orientation of the azygous vein.

Answer 7

The azygous vein runs along the right side of the vertebral bodies and arches anteriorly over the right main bronchus to join the SVC.

Question 8

What are the three main branches of the aortic arch?

Answer 8

Brachiocephalic trunk, left common carotid, left subclavian

Question 9

Describe the arrangement of the veins that drain into the superior vena cava.

Answer 9

Right and Left brachiocephalic veins join together to form the SVC

Each brachiocephalic vein is made up of an internal jugular vein and a subclavian vein

Question 10

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

Answer 10

Left recurrent laryngeal nerve?

Question 11

What part of the diaphragm and at which vertebral level does the IVC go through the diaphragm?

Answer 11

T8

Question 12

Where do the right and left coronary arteries arise?

Answer 12

Ascending Aorta - from just above the cusps of the aortic valve

Question 13

Describe the position of the ascending and descending aorta in relation to the airways.

Answer 13

Ascending aorta is anterior to the airways and the arch loops around the left main bronchus posteriorly and the descending aorta is posterior to the left main bronchus.

Question 14

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

Answer 14

8, 10 and 12

Question 15

Other than the internal and external carotid arteries, what other arteries supply the head and neck?

Answer 15

Vertebral arteries from the subclavian arteries

Question 16

Where does the oesophagus begin and end?

Answer 16

C7 to T11

Question 17

What happens to the oesophagus at T7?

Answer 17

The oesophagus is to the right of the aorta above T7

Beyond T7 the oesophagus starts moving towards the left

The oesophagus also starts to bend more anteriorly

Question 18

How many constrictions does the oesophagus have?

Answer 18

4

Question 19

Where are the four constrictions of the oesophagus?

Answer 19

The junction between the pharynx and the oesophagus

Where the oesophagus is crossed by the arch of the aorta

Where the oesophagus is compressed by the left main bronchus

At the oesophageal hiatus

Question 20

Describe the azygos venous system.

Answer 20

The azygos vein runs along the right side of the vertebral bodies and drains the right side of the chest wall. The accessory hemiazygos (superior to the hemiazygos) and the hemiazygos drain the left side of the chest wall and drain into the azygos. The azygos then arches anteriorly over the lung root and joins the superior vena cava.

Question 21

Describe the relations of the azygos vein.

Answer 21

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

Question 22

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

Answer 22

Motor - diaphragm

Sensory - central tendon of diaphragm, mediastinal pleura, pericardium, peritoneum of central diaphragm

Question 23

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

Answer 23

The right phrenic nerve passes along the right brachiocephalic vein, along the superior vena cava, and along the right side of the heart and pericardium to the diaphragm.

Question 24

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

Answer 24

The vagus nerves run lateral to the two common carotid arteries.

Question 25

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

Answer 25

The left vagus crosses anteriorly to the aortic arch. The left phrenic nerve crosses more anteriorly in front of the aortic arch.

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

What structure does the right vagus nerve lie on?

Answer 28

Trachea

Question 29

What are the main branches of the vagus nerve?

Answer 29

Parasympathetic to the heart and lungs (control of smooth and cardiac muscle + glands of gut and airways)

Large sensory from the gut

Recurrent laryngeal nerve is NOT parasympathetic - it runs up the neck to supply most skeletal muscles of the larynx

Question 30

Which spinal nerves do the sympathetic trunk receive branches from?

Answer 30

T1-L2

Question 31

Where do the nerves to the body wall synapse?

Answer 31

In the sympathetic ganglia (Sympathetic trunk brings pain fibres to the CNS from the viscera )

Question 32

Where do the nerves to the internal organs synapse?

Answer 32

In the local ganglia.

Question 33

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

Answer 33

T5-T12 (Splanchnic nerves)

Question 34

Describe the arrangement of the thoracic duct.

Answer 34

The thoracic duct begins as the cisterna chyli (L2) below the diaphragm just to the right of the aorta (between aorta and oesophagus).

The thoracic duct then crosses to the left side between T4-T7.

The thoracic duct drains into the left brachiocephalic vein.

Question 35

What are the borders of the heart?

Answer 35

3rd CC - 1cm from sternal border

6th CC - 1cm from sternal border

2nd ICS/2nd CC - 2.5cm from sternal border

5th ICS to apex beat at MC line