Mediastinum

Question 1

Mediastinum is occupied by…

Answer 1

• Mass of tissue between 2 pulmonary/pleural cavities
• contains all thoracic viscera, nerves, and vessels except the lungs and those in thoracic wall

Question 2

Mediastinum is covered by…

Answer 2

• Mediastinal pleura
• surrounded by blood & lymphatic vessels, lymph nodes, nerves & fat

Question 3

Mediastinum extends from…

Answer 3

• superior thoracic aperture to diaphragm
• sternum & costal cartilages to bodies of thoracic vertebrae

Question 4

Mediastinum primarily consists of hollow visceral structures united by…

Answer 4

Loose CT (often adipose)

Question 5

Mediastinum is divided by…

Answer 5

Transverse thoracic plane at level of sternal angle & junction of T4-T5 (at IVD)

Question 6

Name the divisions of the mediastinum

Answer 6

• superior
• inferior: anterior, middle, posterior

Question 7

Contents of middle mediastinum

Answer 7

• pericardium
• heart
• roots of great vessels

Question 8

What is the pericardium?

Answer 8

• Fibroserous membrane
• closed sac covering heart and beginning of great vessels

Question 9

Name the layers of the pericardium

Answer 9

Fibrous
Parietal serous
Visceral serous

Question 10

Superior attachments of fibrous pericardium

Answer 10

• continuous with tunica adventitia of great vessels
• continuous with pretracheal layer of cervical fascia

Question 11

Anterior attachments of fibrous pericardium

Answer 11

To posterior surface of sternum by sternopericardial ligaments

Question 12

Posterior attachments of fibrous pericardium

Answer 12

Loose CT to structures of posterior mediastinum

Question 13

Inferior attachments of fibrous pericardium

Answer 13

Continuous with central tendon of diaphragm

Question 14

Pericardial cavity

Answer 14

• space between opposing layers of parietal & visceral serous pericardium
• contains fluid that enables heart to move & beat in frictionless environment

Question 15

Visceral serous pericardium forms the ____

Answer 15

Epicardium

Question 16

Visceral serous pericardium attachments

Answer 16

Extends onto beginning of great vessels, continuous with parietal layer of serous pericardium:
- where aorta & pulmonary trunk leave heart
- where superior vena cava (SVC) and inferior vena cava (IVC) and pulmonary veins leave atria

Question 17

Blood supply of pericardium

Answer 17

• pericardiacophrenic a. (Branch of internal thoracic a)
• musculophrenic a
• bronchial, esophageal, superior phrenic aa of thoracic aorta
• coronary aa (visceral serous pericardium only)

Question 18

Pericardium venous drainage

Answer 18

• pericardiacophrenic vv = tributaries of brachioceophalic v or internal thoracic vv
• various tributaries of azygous venous system

Question 19

Nerve supply to pericardium

Answer 19

• phrenic nerves (C3-C5) = sensory, pain
• vagus nerve (CN X) = parasympathetic
• sympathetic trunks = vasomotor functions

Question 20

Location of superior mediastinum

Answer 20

Superior to transverse thoracic plane

Question 21

Contents of superior mediastinum

Answer 21

• thymus
• great vessels & veins
• vagus, phrenic nerves
• cardiac plexus
• trachea
• esophagus
• recurrent laryngeal nerves
• thoracic duct & lymphatic trunks

Question 22

Location of thymus

Answer 22

• inferior neck & anterior portion of superior mediastinum anterior to fibrous pericardium
• largely replaced by fat after puberty

Question 23

Great vessels of superior mediastinum

Answer 23

• R & L brachiocephalic vv
• SVC
• ascending aorta
• arch of aorta
• thoracic (descending) aorta
• arch of azygous v
• brachiocephalic trunk
• L common carotid a
• L subclavian a

Question 24

Ligamentum arteriosum

Answer 24

• remnant of fetal ductus arteriosus
• passes from root of L pulmonary a to inferior surface of arch of aorta

Question 25

Where does Right vagus nerve enter the thorax?

Answer 25

Anterior to right subclavian a

Question 26

R vagus nerve gives rise to the ____

Answer 26

R. Recurrent laryngeal nerve

Question 27

Where does R vagus nerve travel in the superior mediastinum?

Answer 27

Posterior to R brachiocephalic vein, SVC, and root of lung

Question 28

Where does L vagus nerve enter mediastinum?

Answer 28

Between carotid and subclavian aa

Question 29

Where does L vagus nerve travel in the superior mediastinum?

Answer 29

- Descends in neck posterior to left common carotid a. - at arch of aorta, diverges posterior to left phrenic nerve

Question 30

L vagus nerve gives rise to the ____

Answer 30

Left recurrent laryngeal nerve

Question 31

R recurrent laryngeal nerve

Answer 31

- Hooks around R subclavian artery - ascends between trachea & esophagus to supply larynx

Question 32

L recurrent laryngeal nerve

Answer 32

- passes inferior to arch of aorta, lateral to ligamentum arteriosum - ascends to larynx

Question 33

R phrenic nerve pathway

Answer 33

- Passes along right side of R brachiocephalic vein, SVC, and pericardium over the R atrium - descends on right side of SVC to diaphragm

Question 34

L phrenic nerve pathway

Answer 34

- descends between L subclavian & common carotid aa - crosses left surface of aortic arch to vagus nerve - runs along fibrous pericardium superficial to L atrium & ventricle to diaphragm

Question 35

Cardiac plexus

Answer 35

- nerve network lies anterior to bifurcation of trachea - supplies sympathetics & parasympathetics to heart

Question 36

Trachea

Answer 36

- respiratory structure - divides into L & R bronchus at level of sternal angle

Question 37

Esophagus

Answer 37

- fibromuscular tube that extends from pharynx (back of throat) - enters mediastinum between trachea & vertebrae

Question 38

Location of thoracic duct

Answer 38

Lies on left side of esophagus, deep to arch of aorta

Question 39

Where does thoracic duct drain?

Answer 39

Into L brachiocephalic vein by confluence of L subclavian & internal jugular veins