Superior Mediastinum

Question 1

What separates the superior and inferior mediastinum?

Answer 1

Imaginary line running from sternal angle to T4 vertebrae

Question 2

What is the mediastinum

Answer 2

Central compartment of thoracic cavity, located between the pleural sacs, acts as conduit for transverse structures from thorax to abdomen

Question 3

Sternal angle

Answer 3

Angle formed by junction of sternal body and manubrium

Question 4

Superior mediastinum

Answer 4

Extends upwards, terminates at superior thoracic aperture

Question 5

Inferior mediastinum

Answer 5

Extends downwards, terminates at diaphragm. Subdivided into anterior mediastinum, middle mediastinum and posterior mediastinum

Question 6

Borders of the superior mediastinum

Answer 6

Superior - thoracic inlet
Inferior - continuous with inferior mediastinum at level of the sternal angle
Anterior - manubrium of the sternum
Posterior - vertebral bodies of T1-4
Lateral - pleurae of the lungs

Question 7

3 major branches of aortic arch arise within

Answer 7

Superior mediastinum

Question 8

Brachiocephalic artery

Answer 8

Supplies right side of the head and neck and right upper limb

Question 9

Left common carotid artery

Answer 9

To the left side of the head and neck

Question 10

Left subclavian artery

Answer 10

To the left upper limb

Question 11

Brachiocephalic veins (superior vena cava)

Answer 11

Drain blood from the upper body

Question 12

Left superior intercostal vein (superior vena cava)

Answer 12

Collects blood from the left 2nd and 3rd intercostal vein. It drains into left Brachiocephalic vein

Question 13

Supreme intercostal vein

Answer 13

Drains the vein from first intercostal space directly into the Brachiocephalic veins

Question 14

Azygous vein

Answer 14

Receives blood from right posterior intercostal veins. The left intercostal veins drain first into the hemiazygos and accessory hemiazygos veins before joining the azygos vein around T7-T9

Question 15

Nerves in superior mediastinum

Answer 15

Right vagus nerve, left vagus nerve, phrenic nerve, cardiac nerves, sympathetic trunk

Question 16

Right vagus nerve

Answer 16

Runs parallel to the trachea and passes posteriorly to the superior vena cava and right primary bronchus

Question 17

Left vagus nerve

Answer 17

Enters superior mediastinum between the left common carotid and the left subclavian arteries. It descends anteriorly to the aortic arch, before travelling posterior to the left bronchus

Question 18

Left recurrent laryngeal nerve

Answer 18

Arises from left vagus nerve as it passes the aortic arch. Loops under the arch to the left ligamentum arteriosum before continuing to the larynx in the tracheal-oesophageal groove

Question 19

Phrenic nerve

Answer 19

From anterior surface of anterior scalene muscle, phrenic nerves (roots C3,C4,C5) enter the superior mediastinum lateral to the great vessels. They then descend anteriorly into the middle mediastinum and pass anteriorly to the hilum of the lungs

Question 20

Cardiac nerves

Answer 20

Originate from superior, middle, inferior cardiac ganglion and form the superficial and deep cardiac plexuses in superior mediastinum. The superior plexus sits between the aortic arch and right pulmonary artery. The deep plexus lies on the surface of the trachea at the point of bifurcation.

Question 21

Sympathetic trunk

Answer 21

Runs bilaterally to the vertebral bodies along the entire length of the vertebral column

Question 22

Other structures in superior mediastinum

Answer 22

Thymus, trachea, oesophagus, thoracic duct, muscles

Question 23

Thymus (superior mediastinum)

Answer 23

Most anterior structure. Sits against posterior surface of sternum and extends into anterior mediastinum, can reach into the neck

Question 24

Trachea (superior mediastinum)

Answer 24

Trachea bifurcates into primary bronchi posterior to ascending aorta at level of sternal angle

Question 25

Oesophagus (superior mediastinum)

Answer 25

Ascends towards pharynx, joins at the level of C6

Question 26

Thoracic duct (superior mediastinum)

Answer 26

Thoracic duct passes to the left of oesophagus to the junction of the left internal jugular and subclavian veins

Question 27

Muscles (superior mediastinum)

Answer 27

Sternohyoid and sternothyroid muscles originate from posterior surface of the manubrium (part of the infrahyoid muscle group of neck)
Inferior aspect of longus colli muscle originates within superior mediastinum