Mediastinum II

Question 1

what are the major divisions of the mediastinum?

Answer 1

Superior
Inferior (anterior, middle, posterior)

Question 2

what is in the superficial division of the mediastinum?

Answer 2

Internal thoracic aorta
Thymus
Superior vena cava
Parasternal lymphatics

Question 3

what is in the middle layer of the mediastinum?

Answer 3

Arch of the aorta
Pulmonary trunk
Vagus nerve
Phrenic nerve

Question 4

what is in the deep layer of the mediastinum?

Answer 4

Trachea
Esophagus
Recurrent laryngeal n.
Thoracic duct
Azygos vein
Sympathetic trunk

Question 5

what is contained in the superior mediastinum?

Answer 5

-Thymus, thoracic duct
- Internal thoracic blood vessels, great vessels of the heart, ligamentum arteriosum, azygous veins
- Vagus nerve, phrenic nerve, recurrent laryngeal nerve, sympathetic trunk
- Trachea
- Esophagus

Question 6

what are the 3 layers of the superior mediastinum?

Answer 6

-superficial
-middle
-Deep

*different on the left and right

Question 7

what is contained in the superficial layer of the superior mediastinum?

Answer 7

Internal thoracic arteries and veins
- inferior anterior mediastinum
Thymus
Superior vena cava and major branches
Parasternal lymphatics

Question 8

what are the features of the thymus?

Answer 8

Immediately posterior to sternum
Bi-lobar

Question 9

what is the role of the thymus?

Answer 9

Early development of the immune system
- T-cells multiply, differentiate into specialised immune cells, prevent autoimmunity

Question 10

what are the features of the thymus in children?

Answer 10

Root of the neck
- as far superiorly as thyroid cartilage
Inferior anterior mediastinum
- 4th costal cartilage

Question 11

what are the features of the thymus in adults?

Answer 11

-Atrophies after puberty
- Mostly fatty tissue

Question 12

what happens if the left BCV is distended?

Answer 12

it can extend above the superior media stinum
- becomes vulnerable to suprasternal incisions

Question 13

what are the features of the left and right brachiocephalic veins?

Answer 13

-Subclavian vein and internal jugular vein
- Posterior to medial ends of clavicles

The left BCV is longer than the right
- has to pass anterior to the branches of the aorta

Question 14

what do the brachiocephalic veins drain?

Answer 14

Drainage of the upper limb, head and neck

Question 15

what is contained within the middle layer of the superior mediastinum?

Answer 15

• Aortic arch and major branches (pulmonary trunk and pulmonary arteries (middle mediastinum))
• Ligamentum arteriosum
• Vagus nerve
  -phrenic nerve

Question 16

what are the features of the arch of the aorta?

Answer 16

• Emerges from pericardial sac as ascending aorta
• Sternal angle=arch

Course
- Superior (mid-manubrium), posterilateral (left)

3 main branches

Question 17

what are the ABC’s of the Aorta?

Answer 17

Arch
Brachiocephilic arch
left Common carotid artery
left Subclavian artery

Question 18

what are the features of the Pulmonary trunk and arteries?

Answer 18

• (middle mediastinum)
• Emerges: left of arch
• Passes: posterior to superior vena cava and arch of aorta

Question 19

where does the vagus nerve emerge from?

Answer 19

10th cranial nerve - brainstem

Question 20

what is the role of the vagus nerve?

Answer 20

Parasympathetic innervation to thoracic and abdominal organs

Question 21

where is the vagus nerve?

Answer 21

Lateral to trachea
Left: lateral to arch of aorta

Question 22

where does the phrenic nerve arise from?

Answer 22

C3, C4, and C5

Question 23

what does the vagus nerve innervate?

Answer 23

Esophageal plexus, cardiac plexus, pulmonary plexus

Question 24

what does the phrenic nerve innervate?

Answer 24

Diaphragm, pericardium (parietal serous and fibrous) and pleura

Question 25

where is the phrenic nerve?

Answer 25

-behind the subclavian vein, in front of the lung root - Lies as lateral as possible- in contact with mediastinal pleura - on the lateral aspect of the great vessles

Question 26

what is contained within the deep layer of the superior mediastinum?

Answer 26

Trachea Esophagus Left recurrent laryngeal nerve (vagus) Thoracic duct Azygos vein Sympathetic trunks

Question 27

what is the function of the lower esophageal sphincter?

Answer 27

Controls entrace into the stomach

Question 28

what are the narrowings of the esophagus?

Answer 28

- Upper esophageal sphincter (C6, cricoid) - Aortic arch - Left main bronchus - Esophageal hiatus (diaphragm)

Question 29

where does the esophagus run?

Answer 29

Joins the pharynx to the stomach - Cervical (skeletal muscle), thoracic, abdominal (smooth muscle)

Question 30

what is posterior to the esophagus?

Answer 30

Vertebral bodies

Question 31

what is anterior to the esophagus?

Answer 31

Trachea

Question 32

what is right to the esophagus?

Answer 32

Azygos vein

Question 33

what is left to the esophagus?

Answer 33

Arch of the aorta

Question 34

what is the recurrent laryngeal nerve?

Answer 34

Branch of the vagus nerve There are left and right

Question 35

what are the features of the left recurrent laryngeal nerve?

Answer 35

-superior mediastinum -ligamentum arteriosum -Arch of the aorta

Question 36

what are the features of the right recurrent laryngeal nerve?

Answer 36

-neck region -right subclavian artery

Question 37

what does the recurrent laryngeal nerve innervate?

Answer 37

Trachea Esophagus Larynx

Question 38

what can happen to the left recurrent laryngeal nerve?

Answer 38

It is susceptible to compression as it passes under the aortic arch the symptoms: vocal cord paralysis, hoarsenees of voice

Question 39

where is the thoracic duct?

Answer 39

Posterior infeior mediastinum - Cisterna chyli (T12) - Between aorta and azygous vein - Moves to the left (alongside aorta) behind esophagus

Question 40

what is the role of the thoracic duct?

Answer 40

Drains into left brachiocephalic vein - junction between the internal jugular vein and left subclavian vein Drains body of lymph - except right upper limb, right half of thorax, head and heck = right lymphatic duct

Question 41

what are the features of the Azygos vein?

Answer 41

- Right laternal aspect of vertebral bodies - Venous drainage: posterior thoracic wall (upper lumbar region)- posterior intercostal veins -Superior aspect is located within superior mediastinum

Question 42

where does the azygos vein enter?

Answer 42

Superior vena cava

Question 43

what is the sympathetic trunk of the nervous system?

Answer 43

-Parallel chains of nerves - Lateral to vertebral column (neck of ribs) -Sympathetic innervation thoracic and abdominal viscera Superior mediastinum (pulmonary, esophageal, cardiac plexuses)