Dissection of the Superior Mediastinum Flashcards
(93 cards)
1
Q
Position of right pulmonary artery?
A
Posterior to SVC and aorta
2
Q
Position of left pulmonary artery?
A
Anterior to descending aorta
3
Q
Boundaries of superior mediastinum?
A
- Superiorly: thoracic aperture
- Inferiorly: sternal angle
- Laterally: mediastinal surfaces of parietal pleura
4
Q
12 major structures found in the superior mediastinum?
A
- Thymus
- Right and left brachiocephalic veins
- Left superior intercostal vein
- SVC
- Aortic arch and its 3 branches
- Trachea
- Esophagus
- Phrenic nerves
- Vagus nerves
- Left recurrent laryngeal nerve
- Thoracic duct
- Other small nerves, vessels, and lymphatics
5
Q
From what nerves do the recurrent laryngeal nerves branch?
A
Vagus nerves
6
Q
Most anterior component of the superior mediastinum?
A
Thymus
7
Q
What is located immediately posterior to the thymus?
A
Left and right brachiocephalic veins
8
Q
At what junction do the right and left brachiocephalic veins form?
A
Junction of subclavian and jugular veins
9
Q
Which brachiocephalic vein crosses the midline? At what level does it do this?
How is this different in children?
A
Left one posterior to manubrium
In children in passes the midline superior to manubrium so is less protected
10
Q
Position of beginning of right and left brachiocephalic veins?
A
Posterior to medial end of right/left clavicles
11
Q
Venous tributaries of right brachiocephalic vein?
A
- Vertebral vein
- 1st posterior intercostal vein
- Internal thoracic veins
- Inferior thyroid + thymic veins
12
Q
Surface projection of transition from L and R brachiocephalic veins to SVC?
A
Lower edge of right 1st costal cartilage close to right sternal border
13
Q
Venous tributaries of left brachiocephalic vein?
A
- Vertebral vein
- 1st posterior intercostal vein
- Left superior intercostal vein
- Inferior thyroid + thymic veins
- Pericardial veins
14
Q
How do L and R brachiocephalic veins differ?
A
Right one is shorter and more vertical
15
Q
Surface projections of SVC?
A
- Begins at lower edge of right 1st costal cartilage close to right sternal border
- Enters RA at lower edge of 3rd costal cartilage close to right sternal border
16
Q
Veins draining into SVC other than brachiocephalic veins?
A
- Azygos vein
2. Optional pericardial and mediastinal veins
17
Q
Describe the venous access for central and dialysis lines.
A
Lines introduced through venous punctures in axillary, subclavian, or internal jugular veins and passed through the main veins of the superior mediastinum to reside in the distal portion of the SVC or RA
18
Q
What kind of procedures use the vertical axis between the SVC and IVC to access the IVC?
A
- Transjugular liver biopsy
- Transjugular intrahepatic portosystemic shunts
- Insertion of IVC filter to catch emboli dislodged from veins in the lower limbs and pelvis (in patients with deep vein thrombosis)
19
Q
Describe the vertebral levels/surface projection of the aortic arch.
A
- Starts at T4/T5
- Reaches T3/T4 (mid-manubrium)
- Ends at T4
20
Q
Position of SVC in regards to ascending aorta?
A
Right
21
Q
Position of infundibulum of RV in regards to ascending aorta?
A
Anterior
22
Q
Position of pulmonary trunk in regards to ascending aorta?
A
Anterior
23
Q
Position of right main bronchus in regards to ascending aorta?
A
Posterior
24
Q
Position of right auricle in regards to ascending aorta?
A
Right/Anterior
25
Position of right pulmonary artery in regards to ascending aorta?
Posterior
26
Position of LA in regards to ascending aorta?
Posterior
27
3 portions of thoracic aorta?
1. Ascending aorta
2. Aortic arch
3. Descending aorta
28
Other name for descending aorta?
Thoracic aorta
29
What crosses all 3 branches of the aortic arch anteriorly?
Left brachiocephalic vein
30
Veins draining into the left superior intercostal vein?
1. 2nd posterior intercostal vein
2. 3rd posterior intercostal vein
3. 4th posterior intercostal vein (sometimes)
4. Left bronchial veins
5. Left pericardiacophrenic vein (sometimes)
31
What does the left superior intercostal vein drain into?
Left brachiocephalic vein
32
What vein does the left superior intercostal vein connect with inferiorly? 2 names
Accessory hemiazygos vein = superior hemiazygos vein
33
Pathway of the left superior intercostal vein?
Over left side of aortic arch => lateral to left vagus nerve => medial to left phrenic nerve => enters left brachiocephalic vein
34
First branch of the aortic arch?
Brachiocephalic trunk
35
Surface projection of brachiocephalic trunk?
Posterior to manubrium
36
Direction of ascension of brachiocephalic trunk?
Posteriorly and to the right
37
At what level does the brachiocephalic trunk divide? Into what? What does each supply?
Upper edge of right sternoclavicular joint into:
1. Right common carotid artery: right side of head and neck
2. Right subclavian artery: right upper limb
38
What is the optional 3rd branch of the brachiocephalic trunk? Where else would it arise from?
Thyroid ima artery
Could also branch for right CC or right subclavian arteries, or aortic arch
39
Second branch of the aortic arch? What does it supply?
Left common carotid artery: left side of head and neck
40
Position of left common carotid artery in regards to trachea?
Left
41
Position of brachiocephalic trunk in regards to trachea?
Right
42
Third branch of the aortic arch? What does it supply?
Left subclavian artery: left upper limb
43
How do we call a patent ligamentum arteriosum?
Ductus arteriosus
44
What is coarctation of the aorta? 2 long-term consequences?
Congenital abnormality in which the aortic lumen is constricted distal to the origin of left subclavian artery and ligamentum arteriosum causing diminished supply to lower limbs and abdomen (can also cause cardiac failure)
Overtime vessels ABOVE the narrowing enlarge so that blood can reach the aorta below the level of narrowing (internal thoracic, superior epigastric, and musculophrenic arteries) => anterior intercostal arteries enlarge => posterior intercostal arteries enlarge => notching of the ribs
Note: vessels proximal to the vessel do not enlarge so no rib notching for ICS 1 and 2
Overtime longer time, collateral vessels develop around the chest wall and abdomen to compensate
45
2 situations in which aortic pathologies will create symptoms? Describe each
1. Trauma: aortic trauma at its 3 attachments in a serious deceleration injury
2. Aortic dissection: longitudinal split in the wall of the aorta between intima and media forming a channel within the wall of the vessel (usually blood reenters main vessel distal to point of entry in channel)
46
Does atherosclerosis in the thoracic aorta produce symptoms?
NOPE
47
What are the 3 attachments of the thoracic aorta?
1. Aortic valve
2. Ligamentum arteriosum
3. Point of passing through diaphragm behind the median arcuate ligament
48
Symptoms of aortic dissection in ascending aorta?
Myocardial infarction or stroke and ischemia of gut or kidneys
49
What does dextrocardia mean?
Right sided heart
50
In what 2 situations would a right sided aortic arch be seen?
1. Dextrocardia
| 2. Situs inversus
51
What are 3 common abnormalities of the origins of the great vessels?
1. Common origin for brachiocephalic trunk and left CC artery
2. Left vertebral artery originating from aortic arch
3. Right subclavian artery originating from distal portion of aortic arch and passing behind the esophagus to supply right arm causing difficulty swallowing
52
Surface projection to palpate trachea?
Jugular notch
53
What crosses the trachea and esophagus as they enter the inferior mediastinum?
Azygos vein on right side and aortic arch of left side
54
Purpose of cartilagenous rings of trachea being incomplete?
Allow expansion of esophagus during swallowing
55
Do visceral afferents in the vagus nerves relay pain sensations?
NOPE
56
Pathway of right vagus nerve?
Between right brachiocephalic vein and brachiocephalic trunk => crosses lateral surface of trachea => posterior to root of right lung
57
What passes the right vagus nerve before it crosses the lateral surface of the trachea to meet the esophagus?
Arch of azygos vein
58
Branches of right and left vagus nerves as it enters superior mediastinum?
1. Esophagus plexus
2. Cardiac plexus
3. Pulmonary plexus
4. Recurrent laryngeal nerves
59
Pathway of left vagus nerve?
Posterior to left brachiocephalic vein between the left CC artery and the left subclavian artery => deep to mediastinal pleura => crosses left side of aortic arch => posterior to root of left lung
60
From what nerve does the left recurrent laryngeal nerve arise?
Left vagus nerve
61
Pathway of left recurrent laryngeal nerve?
Inferior margin of aortic arch lateral to ligamentum arteriosum => inferior to aortic arch and posterior to ligamentum arteriosum => ascends on medial surface of aortic arch => groove between trachea and esophagus => neck => terminates in larynx
62
Where and from what nerve do the phrenic nerves arise?
In the cervical region mainly from C4 but also C3 and C5
63
What do the phrenic nerves innervate in the thorax? Abdomen?
1. Mediastinal pleura
2. Fibrous pericardium
3. Parietal layer of serous pericardium
Abdomen: diaphragm + its crura
64
Pathway of right phrenic nerve?
Lateral/anterior to right vagus nerve and lateral/posterior to right brachiocephalic vein => continues inferiorly along right side of the right brachiocephalic vein and SVC => right side of pericardial sac within the fibrous pericardium (anterior to root of right lung) => through diaphragm with IVC
65
What vessels accompany the right and left phrenic nerves?
Pericardiacophrenic vessels
66
Pathway of left phrenic nerve?
Lateral/anterior to left vagus nerve and lateral/posterior to left brachiocephalic vein => continues inferiorly along left side of the aortic arch => left side of pericardial sac within the fibrous pericardium (anterior to root of right lung) => through diaphragm near apex of the heart
67
What is the aortopulmonary window? What nerve passes in it?
Area between the pulmonary arteries and the aorta
Left recurrent laryngeal nerve
68
In what cases is there compression of the aortopulmonary window? What does this cause? Diagnosis?
Lymph node enlargement often associated with the spread of lung cancer
Causes vocal cord paralysis and voice hoarseness due to compression of left recurrent laryngeal nerve
Diagnosis: chest radiography
69
From what nerve does the right recurrent laryngeal nerve arise?
Right vagus nerve
70
Pathway of right recurrent laryngeal nerve?
Hooks around the right subclavian artery as it passes over the cervical pleura => groove between trachea and esophagus => neck => terminates in larynx
71
What is a Pancoast tumor? Symptoms? Diagnosis?
Cancer in apex of right lung
Symptoms: hoarse voice and right vocal palsy with laryngoscopy
Diagnosis: chest radiography with apical lordotic view
72
Pathway of thoracic duct in the superior mediastinum?
Enters inferiorly to the left of the midline => posterior to aortic arch => between esophagus and left mediastinal pleura
73
Will severing a phrenic nerve cause issues with inspiration or expiration? Would you still be able to breathe? Describe the exact effect.
Inspiration
Yes, just more contraction on ONE side of the diaphragm
The ipsilateral hemidiaphragm exhibits paradoxical movement – elevating with inspiration instead of the normal depression because of the actions of the intact hemidiaphragm and the associated pressure changes in the abdomen and thorax
74
How is the breathing affected during pregnancy?
Women increasingly rely on costal breathing because the uterus enlarges and pushes against the abdominal viscera and vertical thoracic diameter cannot be increased as much
75
What are hiccups?
Spasms of the diaphragm for unknown reasons
76
Function of recurrent laryngeal nerves?
Supplies motor function and sensation to larynx
77
Which nerve would be affected by an aortic aneurism in the aortic arch?
Left recurrent laryngeal nerve
78
Location of SVC in regards to root of the lung?
Anterior
79
At what intercostal space does the L brachiocephalic vein meet the right one?
1st!
80
Does the right recurrent laryngeal nerve go to the posterior mediastinum?
NOPE
81
Position of right/left brachiocephalic vein in regards to brachiocephalic trunk/left CC and left subclavian arteries?
Anterior
82
Where are pulmonary veins located in regards to pulmonary arteries?
Inferior to
83
When looking at the CT, if the aortic arch is apparent, what is located on its right?
SVC
84
If fluid from the thoracic duct escapes due to trauma, where would it go? What is this called? Does this ever cause pleural effusion?
Effusion from the thoracic duct (chylothorax) enters the thoracic cavity.
When the thoracic duct is inadvertently damaged during surgery, the right pleural cavity is also typically inadvertently opened allowing lymph from the duct to enter it
85
From what 2 abdominal structures does the phrenic nerve carry sensations?
1. Liver
| 2. Gallbladder
86
Why does aortic dissection sometimes cause myocardial infarction?
It may extend retrogradely to involve the coronary sinus of RCA in aortic valve, occluding the RCA
87
What happened if an aortic dissection caused ischemic lower limbs?
Means the 2 channels within the aorta have extended throughout the length of the aorta into the iliac system and femoral arteries
88
Why are aortic dissection patients acidotic?
Because the gut (or other organs) can become ischemic if the dissection extends to the abdominal aorta => organs release significant amounts of H+
89
Why can aortic dissection patients have renal failure?
Reduced blood flow to kidneys
90
Treatment for aortic dissection?
Emergency surgery
91
Possible underlying cause of aortic dissection?
Marfan syndrome: genetic disorder that affects the body’s connective tissue
92
What is found posterior to the sternal ends of the clavicles near the sternoclavicular joints?
Junctions of internal jugular veins and subclavian veins to form the brachiocephalic veins
93
What abdominal organs does the thoracic wall protect?
1. Liver
2. Stomach
3. Spleen
4. Superior poles of kidneys
