Introduction to the Mediastinum and Great Vessels

Question 1

What is the mediastinum?

Answer 1

central compartment of the thoracic cavity, located between the 2 pleural sacs

Question 2

Borders of the superior mediastinum

Answer 2

superior: thoracic inlet
inferior: continuous with inferior mediastinum at the level of sternal angle
anterior: manubrium
posterior: vertebral bodies of T1-4
lateral: pleurae of the lungs

Question 3

Great vessels that pass into the superior mediastinum and their branches

Answer 3

arch of aorta - brachiocephalic artery, left common carotid, left subclavian artery
superior vena cava - brachiocephalic veins, left superior intercostal vein, azygous vein

Question 4

Nerves that pass into the superior mediastinum

Answer 4

vagus nerve - right and left ( -> left recurrent laryngeal)
phrenic
cardiac nerves
sympathetic trunk

Question 5

Route of the left recurrent laryngeal nerve

Answer 5

arises from left vagus nerve as it passes the aortic arch
loops under the arch to the left of ligamentum arteriosum
travels to larynx in the tracheal-oesophageal groove

Question 6

Route of the phrenic nerve

Answer 6

from roots C3-5 to anterior surface of the anterior scalene muscle
enters superior mediastinum lateral to great vessels
descend anteriorly into middle mediastinum, passing anteriorly to the hilum of the lungs

Question 7

Other structures in the superior mediastinum

Answer 7

thymus gland
trachea - bifurcates at level of sternal angle
oesophagus - ascends to pharynx, joins at C6
thoracic duct - left of oesophagus, to junction of LIGV and subclavian veins
muscles - sternohyoid and sternothyroid originate from the posterior surface of the manubrium