Mediastinum

Question 1

Mediastinum:

1. Location
2. Borders

Answer 1

1. In the center between two pleural cavities (at sternum), but also projects left of sternum to include heart
   anterior: sternum
   posterior: thoracic vertebrae
   superior: superior thoracic aperture
   inferior: diaphragm

Question 2

What are the subdivisions of the mediastinum?

Answer 2

superior and inferior

inferior includes anterior, middle=pericardium, and posterior

Question 3

Transerse thoracic plane

1. Location
2. What does it separate

Answer 3

1. Sternal angle anteriorly to 4/5th intervertebral disc posteriorly

• Divides mediastinum into superior and inferior levels
• Also divides the aortic arch into its ascending and descending branches
• Defines superior limit of the pericardium

Question 4

What is the most anterior structure in the mediastinum? What does it do?

Answer 4

Thymus (not thyroid)

Lymphoid organ that makes T cells - large in children

involution at puberty = becomes fat

Question 5

What are the four layers of the pericardium?

Answer 5

1. Fibrous pericardium
2. Parietal serous layer
3. Pericardial cavity
4. Visceral serous layer = epicardium

Question 6

What are special features of the fibrous pericardium?

Answer 6

• Tough outer layer = does not stretch
• Fused to diaphragm and tunica adventitia of the great vessels

Question 7

Which two layers is the pericardial cavity between?

Answer 7

Parietal and visceral layers of serous pericardium

Question 8

Inferior vena:

1. blood from where
2. where does it enter the heart

3, Where does it pierce the diaphragm

Answer 8

1. deoxy blood from lower half of the body
2. inferior right atrium
3. T8

Question 9

Answer 9

Question 10

Answer 10

Question 11

Answer 11

Question 12

What are the immediate bracnhes of the aortic arch?

Answer 12

1. brachiocephalic
2. left common carotid
3. left subclavian

Question 13

Descending aorta

1. Where does it begin and end
2. Name the major branches

Answer 13

1. Begins at the transverse thoracic plane, ends at the T12 level of the diaphragm
2. bronchial arteries, esophageal arteries, posterior intercostal arteries

Question 14

Pulmonary trunk

1. What is it?
2. Where are its branches?

Answer 14

1. main pulmonary artery from the right ventricle
2. Right pulmonary artery = posterior to ascending aorta and SVC
3. Left pulmonary artery = anterior to thoracic aorta and SVC

Question 15

What is the function of the structure?

Answer 15

Ligamentum arteriosum - remnant of ductus arteriosus

Question 16

Answer 16

Question 17

Trachea

1. What is it posterior to?
2. Where does it bifurcate into the primary bronchi?

Answer 17

1. great vessels
2. T4 level

Question 18

Tracheal lymph nodes

Answer 18

Question 19

What are the openings in the diaphragm and what passes through each?

Answer 19

I 8 10 Eggs At 12

I 8: IVC at T8

10 Eggs: Esophagus at T10 (with vagus nerve)

At 12: Descending aorta at T12 (with thoracic duct)

Question 20

What is the esophagus continuous with?

Answer 20

Pharynx and stomach

Question 21

Azygous system

1. Right vs. Left of vertebral column
2. What does it drain from

Answer 21

Right: azygous vein

Left: accessory hemiazygous vein

Drains from posterior intercostal veins

Question 22

Azygous vein

1. Drain from
2. drain to

Answer 22

1. Veins from thoracic wall (posterior intercostal) and visceral veins
2. drains into SVC superiorly and IVC inferiorly (in abdomen) -> serves as collateral if IVC is blocked

Question 23

What is the largest lymphatic vessel in the body

Answer 23

Thoracic duct

Question 24

Thoracic duct

1. Drain from
2. Where does it begin
3. Drain to

Answer 24

1. receives lymph from the entire lower body and upper left quadrant
2. Begins as the cisterna chyli (major collecting point for lymph flow below abdomen)
3. Drains to venous system: left internal jugular and left subclavian veins

Question 25

Cadaver image

Answer 25

Question 26

Thoracic visceral plexus 1. What innervates it 2. What are its subdivisions and it locations

Answer 26

**1. Vagus nerve (parasympathetics)** 2. Cardiac plexus (on aortic arch), pulmonary plexus (near tracheal bifurcation), esophageal plexus (on esophagus)

Question 27

Thoracic Splanchnic nerves 1. Vertebral level 2. What does it innervate 3. Divisions

Answer 27

1. T5-T12 sympathetic ganglia 2. Abdominal and pelvic cavities only (not thoracic) 3. Greater splanchnic (T5-9), Lesser (T10-11), and Least (T12)

Question 28

Where does the right lymphatic duct receive its lymph?

Answer 28

Right upper quadrant of body

Question 29

What are the main nerves of the mediastinum?

Answer 29

1. phrenic nerves 2. vagus nerve 3. left recurrent laryngeal nerve

Question 30

Phrenic nerves 1. function 2. Vertebral level 3. Where does it enter mediastinum 4. what does it travel along

Answer 30

1. Breathing (somatic efferent fibers to diaphragm) 2. C 3,4,5 keeps the diaphragm alive 3. superior thoracic aperture 4. Runs down fibrous pericardium

Question 31

What vessels supply the pericardium and diaphragm? What does it travel with?

Answer 31

Pericardiaco**_phrenic_** vessels (travel with _phrenic_ nerves)

Question 32

Which nerve travels anterior to the root of the lung? Posterior?

Answer 32

Anterior: Phrenic nerve Posterior: Vagus nerve

Question 33

Vagus nerve 1. function 2. Vertebral level 3. Where does it enter mediastinum 4. what does it travel along

Answer 33

1. PNS, visceral afferent fibers (**to visceral plexuses**), somatic efferent fibers (to larynx) 2. Brainstem (CN X) 3. Superior thoracic aperture 4. Posterior to root of the lung

Question 34

Right vs. Left vagus nerve 1. Travel differences 2. Relation to esophageal plexus

Answer 34

Right: travels along trachea, enters posterior part of esophageal plexus Left: travels along aortic arch, enters anterior part of esophageal plexus

Question 35

Left recurrent laryngeal nerve 1. From what major nerve 2. Where does it arise 3. Function 4. Places of injury

Answer 35

1. Vagus nerve 2. Near aortic arch, loops around aorta & posterior to ligamentum arteriosum 3. somatic efferent fibers to larynx muscles 4. tracheal-esophageal groove, aortic anerurism, inflammation of ligamentum arteriosum -\> hoarseness of voice

Question 36

Describe structures of mediastinum from anterior to posterior

Answer 36

Thymus -\> Great vessels/Heart -\> Trachea -\> Esophagus -\> Azygous system/Thoracic duct -\>Symp trunk

Question 37

Where is the right recurrent laryngeal nerve located?

Answer 37

Wraps under the subclavian artery (NOT in mediastinum)