mediastinum and imaging :

Question 1

what is the mediastinum ?

Answer 1

Thick midline partition that separates the two pleural cavities.

Question 2

what are the boundaries of the mediastinum?

Answer 2

superior : superior thoracic aperture inferior :inferior thoracic aperture anterior :manubrium of sternum posterior : thoracic vertebrae

Question 3

function of the mediastinum?

Answer 3

• allows the passage of structures through from one body region to another - connects thoracic organs to other body regions

Question 4

recap what is the thoracic inlet?

Answer 4

• consists of the 1st thoracic vertebrae - 1st ribs - manubrium - the great vessels - oesophagus - trachea - nerves - lymphatics

Question 5

where does the apex of the lung sit?

Answer 5

• 3cm above the clavicle in the neck

Question 6

where does the right phrenic nerve sit? where does the thoracic duct and azygos vein sit?

Answer 6

• T8 - T12

Question 7

where is the division of the mediastinum?

Answer 7

• transverse plane between the sternal angle ( CC2) and T4/5

Question 8

what does the mediastinum split into?

Answer 8

• superior - above sternal angle - inferior - below sternal angle anterior - : anterior to heart in pericardial sac middle - heart in pericardial sac posterior - posterior to pericardial sac and diaphragm

Question 9

what are the contents of the mediastinum?

Answer 9

• trachea (from C6 to T4) - oesophagus C6 pierces diaphragm at T10 - heart and pericardium - thoracic duct - lymphathic drainage - nerves - great vessels

Question 10

label a thoracic inlet?

Answer 10

Question 11

what does the superior mediastinum contain?

Answer 11

• thymus
• great veins
• SVC
• phrenic nerves
• main lymphathic trunks
• vagus nerve
• great arteries
• trachea
• main bronchi
• upper oesophagus

Question 12

label a superior mediastinum:

Answer 12

Question 13

what does the posterior mediastinum contain?

Answer 13

• oesophagus
• descending aorta
• thoracic duct
• azygos venous system
• —Posterior mediastinal lymph nodes
• —Thoracic sympathetic trunks
• —Splanchnic nerves

Question 14

what is the passage of the oesophagus?

Answer 14

• begins at C7 vertebra
• •Enters superior thoracic inlet into superior mediastinum
• enters the posterior mediastinum
• at T7 it deviates to the left and inclines anteriorly so it passes in front of the descending thoracic aorta
• passes through the diaphragm at T10

Question 15

what are the constrictions of the oesophagus?

Answer 15

• the junction between the pharynx and oesophagus
• where the oesophagus passes the arch of the aorta
• where the oesophagus is compressed by left main bronchus
• at the oesophageal hiatus (the diaphragm)

Question 17

label the passage of the oesophagus:

Answer 17

Question 18

what is the superior vena cava made from?

Answer 18

• formed by the asymmetric union of the left and right brachiocephalic veins
• —Each brachiocephalic vein – formed by Internal jugular vein + subclavian vein.

Question 19

what does brachiocephalic actually mean?

Answer 19

brachio - arm

cephalic - head

therefore drains venous blood from brain and arm

Question 20

label the azygos venous system

Answer 20

refer to netters 3- 15

Question 21

what is the function of the azygos veins?

Answer 21

• drains the posterior walls of the chest and the upper abdomen

and also the posterior mediastinal organs

Question 22

what do the hemiazygos veins do?

Answer 22

—Accessory hemiazygos (upper) + hemiazygos (lower) veins on left cross thoracic vertebral bodies to join single azygos vein on right

Question 24

is the azygos symmetrical or asymmetrical?

Answer 24

asymmetrical

Question 25

what is the thoracic duct?

Answer 25

• the largest lymphatic vessel
• begins on the level of T12
• it enters the thorax through the diaphragm at T12
• —At T5, it crosses the midline to the left side and enters the superior mediastinum

Question 26

what are the great arteries?

Answer 26

—Ascending aorta – middle (origin at the left 3rd CC)

—Arch of the aorta – superior ( called this from the 2nd CC)

—Descending aorta - posterior ( starts at T4)

—

Question 27

label the arteries of the thoracic aorta?

Answer 27

refer to netters 3- 14

Question 28

where is the aorta in regard to the trachea and left main brainchus

Answer 28

• the aortic arch arises anterior to the trachea and arches over the left main bronchus

Question 29

where does the trachea lie?

Answer 29

the trachea lies behind and between the brachiocephalic and left common carotid artery

Question 30

where are the phrenic nerves formed?

Answer 30

in the cervical plexus from C3 C4 C5

Question 31

where does the motor phrenic nerve innervate

where do the sensory phrenic nerves innervate

Answer 31

motor - diaphragm

sensory - —central tendon of the diaphragm

mediastinal pleura

pericardium

the peritoneum of the central diaphragm

Question 32

what surfaces does the right phrenic nerve run on to reach the diaphragm ?

Answer 32

lies on the surface of :

• right brachiocephalic nerve
• superior vena cava
• right side of the heart and the pericardium

Question 33

what is the general rule of the positioning of the phrenic nerve and the vagus nerve?

Answer 33

phrenic nerve is anterior to the lung root

the vagus nerve is posterior to the lung root

Question 34

where are the vagus nerves positioned?

where are vagus nerves compared to common carotids?

where does the left vagus nerve pass?

when does the left phrenic nerve pass the vagus?

Answer 34

• vagus nerves are posterior to the lung roots and form plexus following the oesophagus into the abdomen giving branches to heart and lungs on the way
• the vagus nerves are lateral to the common carotids
• the left vagus nerve passes anterior to the aortic arch
• the left phrenic nerve crosses the vagus to cross the aortic arch more anteriorly

Question 35

where do the left vagus phrenic and vagus nerves sit?

Answer 35

• Cross arch of aorta
• —Left phrenic descends in front of lung root
• Left vagus crosses behind root lung gives off left recurrent

Question 37

how does the laryngeal nerve sit?

Answer 37

• it recurs around the ligamentum arteriosum and the aortic arch
• it then breaks up into many branches around the oesophagus

Question 39

where does the right vagus nerve lie?

Answer 39

• it lies on the trachea
• it crosses behind the lung root

Question 40

what happens to the recurrent laryngeal branch?

Answer 40

• it recurs back around the right subclavian artery
• it also breaks up into branches on the oesophagus

Question 42

what does the vagus nerve provide parasympathetic control to?

Answer 42

control of smooth and cardiac muscle and the glands of gut and airways

Question 43

where does the vagus nerve act as a sensory nerve?

Answer 43

• the guts and the lungs

Question 44

what is the recurrent laryngeal nerve?

Answer 44

• it is not parasympathetic
• it runs back up the neck to supply most of the skeletal muscles of the larynx

Question 45

why is the recurrent laryngeal nerve important?

Answer 45

• it contributes to the muscles allowing us to speak
• in neck surgery if these nerves are damaged then it may cause of voice which is called paralysis

Question 46

label this diagram

Answer 46