Superior and Posterior Mediastinum Flashcards
1
Q
Where is the superior mediastinum found?
A
Superior to transverse plane between the sternal angle and T4-T5 IVD
2
Q
WHat are the contents of the superior mediastinum? (From anterior to posterior)
A
- Thymus
- Brachiocephalic vv and superior vena cava
- Arch of aorta and roots of brachiocephalic trunk, left common carotid a. and left subclavian a.
- Vagus n., phrenic n. and recurrent laryngeal nn.
- Trachea, esophagus and thoracic duct
3
Q
What is the thymus?
A
Bi-lobed, primary lymphoid organ located most superficially in superior mediastinum
4
Q
Where is the thymus located?
A
Immediately posterior to manubrium, antersuperior to pericardium
5
Q
What is the function of the thymus?
A
Site of development of T lymphocytes
6
Q
What is the arterial supply of the thymus?
A
The internal thoracic and anterior intercostal arteries
7
Q
What happens to the thymus after puberty?
A
It atrophies and undergoes fatty replacement
8
Q
How many brachiocephalic veins are there?
A
Two, a right and left
9
Q
What makes up the brachiocephalic vein?
A
Formed by the union of the internal jugular v and subclavian v.
10
Q
What does the brachiocephalic veins drain?
A
Drain blood indirectly from head, neck and upper extremity
11
Q
Which brachiocephalic vein is longer and by how much?
A
Left brachiocephalic v. is longer and twice as long as the right
12
Q
Where does the left brachiocephalic vein pass in regards to the aortic arch?
A
Left brachiocephalic v. passes anterior to major branches of aortic arch
13
Q
Where does the left brachiocephalic vein receive lymph from?
A
Thoracic duct
14
Q
Where does the right brachiocephalic vein receive lymph from?
A
Right Lymphatic duct
15
Q
What makes up the superior vena cava?
A
Union of right and left brachiocephalic vv.
16
Q
At which level is the cuperior vena cava?
A
At level of 1st costal cartilage
17
Q
Where is the superior vena cava located?
A
Located on right side of superior mediastinum
18
Q
Where does the superior vena cava drain blood from?
A
All structures superior to the diaphragm except the heart and lungs
19
Q
What drains into the superior vena cava?
A
Right and left brachiocephalic veins
Azygos vein via the arch of azygos vein
20
Q
How does the arch of the azygos travel in regards to the root of the right lung?
A
Arch of azygos v. passes superior to root of right lung
21
Q
In regards to the pericardial sac, where does the azygos vein communicate with the superior vena cava?
A
Receives azygos v. just superior to entry into pericardial sac
22
Q
At what level does the superior vena cava drain into the right atrium?
A
Level of 3rd costal cartilage
23
Q
Where is the aortic arch located in regards to the pulmonary arteries?
A
Located anterior/superior to right pulmonary a. and posterior to left pulmonary a.
24
Q
What are the major branches of the aortic arch?
A
Brachiocephalic trunk (right side only)
- Divides into right common carotid a. and right subclavian a.
Left common carotid a.
Left subclavian a.
25
What does the aortic arch continue as?
Continues as descending thoracic aorta (in posterior mediastinum)
26
At what vertebral level does the ascending aorta become the aortic arch?
T4
27
At what vertebral level does the aortic arch become the descending thoracic aorta?
T4
28
Where is the right vagus nerve located in the superior mediastinum?
Located posterior to right brachiocephalic v. and anterior to right subclavian a.
29
Where does the right recurrent laryngeal nerve loop?
Loops posteriorly around right subclavian a.
30
What does the right recurrent laryngeal nerve ascend between?
Ascends between trachea and esophagus to larynx
31
What does the right recurrent laryngeal nerve innervate?
Innervates intrinsic muscles of larynx (except cricothyroid m.)
32
Where is the left vagus nerve located in the superior mediastinum?
Loops posteriorly around aortic arch, just lateral to ligamentum arteriosum
33
What does the left recurrent laryngeal nerve ascend between?
Ascends between trachea and esophagus to larynx
34
What does the left recurrent laryngeal nerve innervate?
Innervates intrinsic muscles of larynx (except cricothyroid m.)
35
What happens if both recurrent laryngeal nerves are compressed by tumors in the upper thoracic region?
May present as hoarseness of voice
36
Where do both vagus nerves travel in regards to the lung root?
Both vagus nn. pass posterior to lung root
37
What type of neurons are carried by the vagus nerve?
Contain presynaptic parasympathetic neurons
38
What plexi does the vagus nerve contribute to?
Contribute to cardiac plexus, pulmonary plexus and esophageal plexus
39
What does parasympathetic input do in the cardiac plexus?
Parasympathetic input slow heart rate and constricts coronary aa
40
What does parasympathetic input do in the pulmonary plexus?
Parasympathetic input constricts bronchioles and dilates pulmonary vessels
41
What does parasympathetic input do in the esophageal plexus?
Parasympathetic input increases smooth muscles activity and gland secretion
42
What do neurons in the left vagus nerve emerge from the esophageal plexus as?
Anterior vagal trunk
43
Where is the anterior vagal trunk found?
Found on anterior surface of esophagus
44
What do neurons in the right vagus nerve emerge from the esophageal plexus as?
posterior vagal trunk
45
Where is the posterior vagal trunk found?
Found on posterior surface of esophagus
46
The Phrenic nerve is located between which structures?
Located between subclavian a. and brachiocephalic v.
47
What ventral rami form the phrenic nerve?
C3-C5
48
What type of innervation (motor or sensory) does the phrenic nerve supply?
Both motor and sensory
49
What does the phrenic nerve innervate?
Thoracic diaphragm
Parietal pericardium
Mediastinal and diaphragmatic pleura
50
What innervation does the phrenic nerve provide on the thoracic diaphragm?
Motor and sensory innervation of thoracic diaphragm
51
What innervation does the phrenic nerve provide on the parietal pericardium and mediastinal and diaphragmatic pleura?
Sensory
52
How does the phrenic nerve in regards to the lung, mediastinal pleura and parietal pericardium?
Passes anterior to lung root between mediastinal pleura and parietal pericardium
53
What does the phrenic nerve run with?
pericardiacophrenic a. and v.
54
What do the pericardiacophrenic a. and v. branch from/to?
Branches of internal thoracic a. and v.
55
What do the pericardiacophrenic a. and v. supply?
Supplies pericardium and diaphragm
56
What are the 3 regions of the inferior mediastinum?
Anterior
Middle
Posterior
57
What does the anterior mediastinum consist of?
Lower part of thymic remnant
| Adipose tissue
58
What is contained within the anterior mediastinum?
Internal thoracic vessels and associated lymphatics
59
What is contained in the middle mediastinum?
Heart
Pericardium
Roots of the great vessels
60
Where is the posterior mediastinum found?
Located T5-T12, posterior to pericardium and between pulmonary cavities
61
What are the contents of the posterior mediastinum?
- Descending thoracic aorta
- Esophagus and esophageal plexus (with anterior/posterior vagal trunks)
- Thoracic duct and lymph nodes
- Azygos system of veins
- Thoracic sympathetic trunk and thoracic splanchnic nn. (not technically part of the posterior mediastinum, but in close relationship)
62
Where does the descending thoracic aorta begin?
Continuation of aortic arch beginning at T4
63
Where does the descending thoracic aorta travel?
Descends through thorax on left sides of T5-T12 vertebral bodies
64
What does the descending thoracic aorta do in regards to the esophagus?
Displaces esophagus to the right
65
How does the descending thoracic aorta travel in regards to the thoracic diaphragm?
Passes behind thoracic diaphragm via aortic hiatus
66
At what vertical level is the aortic hiatus found?
T12
67
What does the descending thoracic aorta become after the aortic hiatus?
Continues inferior to aortic hiatus as abdominal aorta
68
What structures pass through the aortic hiatus?
Thoracic duct and azygos v. and the descending thoracic aorta
69
What are the unpaired anterior visceral branches of the descending thoracic aorta?
Esophageal aa. (2-5 of these)
70
What are the Paired lateral visceral branches of the descending thoracic aorta?
Bronchial aa. (to trachea, bronchi, lung tissue, lymph nodes)
71
What are the Paired parietal branches of the descending thoracic aorta?
Posterior intercostal aa.
9 pair in 3rd-11th intercostal spaces
Subcostal aa.
72
What are the additional branches of the descending thoracic aorta?
Pericardial aa.
Mediastinal aa.
Superior phrenic a. (to superior surface of thoracic diaphragm)
- Anastomoses with musculophrenic and pericardiacophrenic aa.
73
What is the esophagus?
fibromuscular tube extending from pharynx to stomach
74
Where is the esophagus located in the superior aperature between T1-T4?
Located between trachea and T1-T4 vertebral bodies in superior mediastinum
75
Where is the esophagus located in the superior aperature between T5-10?
Located posterior to pericardium adjacent to T5-T10 in posterior mediastinum
76
What are the esophageal constrictions?
```
Upper esophageal sphincter
Aortic arch
Left main bronchus
Thoracic diaphragm
Constrictions are only evident during swallowing
```
77
How does the esophagus pass through the thoracic diaphragm?
Via the esophagel hiatus
78
What vertebral level is the esophagel hiatus found?
T10
79
What is the thoracic duct?
Largest lymphatic vessel in the body
80
Where is the thoracic duct located?
Located posterior to esophagus between descending thoracic aorta and azygos v.
81
What does the thoracic duct do?
Drains lymph from entire body except upper right quadrant and head
82
How does the thoracic duct start?
As the cisterna chyle at the ov
83
How does the thoracic duct pass from the abdomen to the thorax?
Aortic hiatus (T12)
84
Where does the thoracic duct ascend along and what vertebral levels does this occur?
T5-T12
85
At what level does the thoracic duct drain?
T4-T5
86
What does the thoracic duct drain into?
- Left subclavian v. or
- Junction between left subclavian v. and internal jugular v. (left venous angle)
- Internal jugular v. (least common)
87
What does the Azygos system of veins drain?
Drains the back, thoracoabdominal walls and mediastinal viscera
88
What happens If the venous return from the lower body is occupled?
The Axygos System of veins Provides an alternate route for venous return from lower body
89
What is the thoracic sympathetic trunk
Series of paravertebral ganglia linked by interganglionic rami
Continuous with cervical and lumbar sympathetic trunks
90
Where is the thoracic sympathetic trunk located?
Parallels vertebral bodies bilaterally
| Located peripheral to costal pleura adjacent to necks of ribs
91
How is the thoracic sympathetic trunk connected to each intercostal nerve?
rami communicantes
92
What are white ramus communicans?
Contains myelinated presynaptic sympathetic neurons passing from spinal cord to intercostal nn. into ganglion in sympathetic trunk
93
Where are white ramus communicans found?
Found from T1-L2 only
94
What are grey ramus communicans?
Contains unmyelinated postsynaptic sympathetic neurons passing from sympathetic trunk ganglion into intercostal nn.
95
where are grey ramus communicans found?
Found at all vertebral levels
96
What neurons are contained in thoracic splanchnic nerves?
Contain presynaptic sympathetic neurons
97
True or false: The thoracic splanchnic nerves contain postganglionic symathetic neurons?
False, Contain presynaptic sympathetic neurons
98
Does the presynaptic sympathetic neuron synapse prior to entering the thoracic splanchnic nerves?
Synapse occurs in prevertebral (preaortic) ganglia in abdomen
99
What are the different thoracic splanchnic nerves?
Greater thoracic splanchnic n.
Lesser thoracic splanchnic n.
Least thoracic splanchnic n.
100
Where is the greater thoracic splanchnic nerve found?
Presynaptic sympathetic neurons originating at T5-T9
101
Where is the lesser thoracic splanchnic nerve found?
Presynaptic sympathetic neurons originating at T10-T11
102
Where is the least thoracic splanchnic nerve found?
Presynaptic sympathetic neurons originating at T12
103
What do the thoracic splanchnic nerves supply?
Supply sympathetic innervation to most abdominal viscera
104
What type of afferent fibers are contained in the thoracic splanchnic nerves ?
Contain visceral afferents (pain) from abdominal/pelvic viscera
105
What are the apertures in the diaphragm that exit the mediastinum?
Caval hiatus
Esophageal hiatus
Aortic hiatus
106
What is the caval hiatus?
Most anterior aperature
107
Where does the caval hiatus exit?
Exits from middle mediastinum at T8 vertebral level
108
Where does the esophageal hiatus exit?
Exits from posterior mediastinum at T10 vertebral level
109
What is the Aortic hiatus?
Most posterior aperature
110
Where does the Aortic hiatus exit?
Descending thoracic aorta exits posterior mediastinum at T12 vertebral level
111
What hiatus does the anterior and posterior vagal trunks use to exit the mediastinum?
Esophageal hiatus
112
What hiatus does the thoracic duct and azygos vein use to enter the mediastinum?
Aortic hiatus
