Thorax - Superior Mediastinum (1)

Question 1

What are the contents of the superior mediastinum?

Answer 1

Thymus. Great vessels. Inferior portion of the trachea and oesophagus. Lymphatics.

Question 2

What is the name of the imaginary plane forming the inferior border of the superior mediastinum?

Answer 2

The transverse thoracic plane.

Question 3

Do adults have a thymus?

Answer 3

Yes, but it is scarcely recognizable because it is usually replaced by adipose tissue. However, it continues to produce T-lymphocytes.

Question 4

How far up the great vessels (superiorly) does the pericardium travel? Which great vessels does it cover?

Answer 4

The pericardium covers the ascending aorta, but not the aortic arch.

Question 5

What is the location of the start of the aortic arch? And the location where it becomes the descending aorta?

Answer 5

The aortic arch starts at the 2nd sternocostal joint. It becomes the descending aorta near the T4 vertebra.

Question 6

What is the difference between the origins of the right and left subclavian arteries?

Answer 6

The left subclavian artery comes directly from the aortic arch. The right subclavian artery comes from the brachiocephalic trunk.

Question 7

What is the course of the left recurrent laryngeal nerve?

Answer 7

It comes from the left vagus nerve, which descends, then a branch from it loops under the aortic arch, and then ascends as the recurrent laryngeal nerve.

Question 8

What is the course of the right recurrent laryngeal nerve?

Answer 8

It comes from the right vagus nerve, which descends, then a branch from it loops under the right subclavian artery, and then ascends as the recurrent laryngeal nerve.

Question 9

Apart from the recurrent laryngeal nerves, what other important nerves traverse the superior mediastinum?

Answer 9

The left and right phrenic nerves, supplying the diaphragm.

Question 10

Where do the phrenic nerves come from?

Answer 10

They arise from the anterior rami of C3-C5 nerves.

Question 11

What does each phrenic nerve supply?

Answer 11

Each phrenic nerve supplies one side of the diaphragm, in the central portion.

Question 12

What are the structures that lie in the transverse thoracic plane?

Answer 12

T4 vertebral body
Manubriosternal joint
Azygous vein draining into the SVC
Junction of superior and inferior mediastinum