The Superior and Posterior Mediastinum

Question 0

What are the 12 contents of the superior mediastinum?

Answer 0

1) Thymus 7) Esophagus
2) Right and Left brachiocephalic veins 8) Phrenic Nerves
3) Left superior intercostal vein 9) Vagus nerves
4) Superior vena cava 10) Left recurrent laryngeal nn.
5) Arch of the aorta w/ its 3 branches 11) Thoracic duct
6) Trachea 12) Azygos vein

Question 1

What are the boundaries of the superior mediastinum?

Answer 1

Anterior: Manubrium of the sternum, Posterior: The bodies of T1-T4 vertebrae
Superior: an oblique line b/n jugular notch and T1 vertebrae, Inferior: transverse plane b/n sternal angle to intervertebral disc (b/n T4 and T5)
Laterally: mediastinal parts of the parietal pleura on either side

Question 2

Understand the anatomical relationships b/n the contents of the superior mediastinum.

Answer 2

Pic. on pp. 7 of presentation

Question 3

What are the first structures found posterior to the thymus?

Answer 3

Right and Left brachiocephalic veins (brachio-arms, cephalic-head—drain blood from the arm and head)
NOTE: the thymus is the most anterior compartment of the superior mediastinum (barely identifiable in adults)

Question 4

Label the cross-sectional view below:

Answer 4

pp. 9

Question 5

Label the following image of the lateral view of the right side:

Answer 5

pp. 10

Question 6

Label the lateral view of the left side:

Answer 6

pp. 11

Question 7

Explain the course of the left recurrent laryngeal nerve.

Answer 7

The left vagus nerve gives off the left recurrent laryngeal nerve at the inferior margin of the arch of the aorta just lateral to the ligamentum arteriosum. Then the recurrent laryngeal nerve passes inferior to the arch of the aorta and ascends in a groove b/n trachea and esophagus to enter the neck where it innervates the larynx.

Question 8

What are the boundaries of the posterior mediastinum?

Answer 8

Anterior: the pericardial sac and diaphragm, Posterior: bodies of mid and lower thoracic vertebrae
Superior: transverse plane from sternal angle to intervertebral disc b/n T4 and T5, Inferior: the diaphragm
Laterally: mediastinal parts of the parietal pleura on either side
NOTE: In actuality, the posterior and superior mediastinum are continuous.

Question 9

What are the 5 main contents of the posterior mediastinum?

Answer 9

1) Esophagus
2) Thoracic aorta
3) Azygos system of veins
4) Thoracic duct and associated lymph nodes
5) Thoracic splanchnic nerves
NOTE: sympathetic trunks NOT considered part of the posterior mediastinum b/c they lie lateral (not anterior) to the vertebral bodies.

Question 10

The esophagus, thoracic aorta, and inferior vena cava course through openings in the diaphragm. At what levels do they pass through the diaphragm?

Answer 10

Esophagus-T10
Aorta-T12
Inferior vena cava-T8

Question 11

Where does the esophagus receive sensory and motor innervation?

Answer 11

The vagus nerve (parasympathetic) and the sympathetic chan via the esophageal plexus.

Question 12

Fibers of left and right vagus nerve mix resulting in 2 trunks:____and___

Answer 12

Anterior Vagal Trunk: anterior to the esophagus (mainly fibers from the left vagus nerve)
Posterior Vagal Trunk: posterior to the esophagus (mainly fibers from the right vagus nerve)
NOTE: Both trunks continue into abdomen with the esophagus

Question 13

Where does the thoracic aorta start and end?

Answer 13

Starts lower edge of T4 vertebrae (as a continuation of the arch of aorta) ends as it passes via aortic hiatus (posterior to the diaphragm at the level of T12 vertebrae)

Question 14

What are some of the branches of the thoracic aorta?

Answer 14

• posterior intercostal arteries (Identify on cadaver)
• esophageal branches
• mediastinal branches
• left bronchial artery
• right bronchial artery

Question 15

What is the function of the azygos system of veins?

Answer 15

• Longitudinal vessels on each side of the body that drain blood from the body wall and return it to the vena cava.
• It also makes anastomotic connections with abdominal veins and is capable of returning blood from the lower part of the body if inferior vena cava is blocked.

Question 16

What are the 3 main veins in the azygos system of veins?

Answer 16

Azygos veins (on the right)
Hemiazygos veins and Accessory hemiazygos veins (on the left)

Question 17

What is the major channel where lymph from the majority of the body is returned to venous system?

Answer 17

Thoracic Duct

Question 18

Where does the thoracic duct begin and end?

Answer 18

Begins at cisterna chyli (a confluence of lymphatic trunks) in the abdomen and extend into the neck where it empties into the junction of -left subclavian vein and -internal jugular vein

Question 19

T/F The sympathetic nerve is part of the posterior mediastinum.

Answer 19

F. The splanchnic nerves lie anterior to the vertebral bodies and are a part of the posterior mediastinum but the sympathetic chain is not.

Question 20

Label the right and left lateral view of the mediastinum.

Answer 20

pp. 23 and 24

Question 21

Identify the structures common to more than one mediastinum.

Answer 21

Superior and Anterior: Thymus
Superior and Middle: Phrenic nn, Superior vena cava
Superior and Posterior: Vagus nn, Thoracic Duct, Esophagus, Azygos Vein

Question 22

Content of Anterior mediastinum are:

Answer 22

Thymus/Fat

Pericardial ligaments

Question 23

Content of the Middle mediastinum are:

Answer 23

Pericardium and heart
Ascending aorta
Pulmonary arteries and veins
Superior and Inferior vena cava
Phrenic nerves