Anatomy - Posterior Mediastinum Flashcards
1
Q
Boundaries of posterior mediastinum?
A
- Superiorly: sternal angle2. Inferiorly: diaphragm3. Laterally: mediastinal pleura4. Anteriorly: pericardial sac
2
Q
6 major structures of the posterior mediastinum?
A
- Esophagus with its plexus (right and left)2. Thoracic aorta with its branches3. Azygos system of veins4. Thoracic duct and associated lymph nodes5. Sympathetic trunks6. Thoracic splanchnic nerves
3
Q
Vertebral borders of esophagus?
A
C6 to T11
4
Q
What is the esophagus?
A
Muscular tube
5
Q
Pathway of esophagus in posterior mediastinum?
A
Anterior aspect of vertebrae in midline => anterior and to the left to be anterior to the thoracic aorta to enter the diaphragm
6
Q
Vertebral level of esophagus passing through esophageal hiatus to enter diaphragm?
A
T10
7
Q
Esophagus 2 attachments?
A
- Pharynx2. Diaphragm
8
Q
What is the right side of the esophagus covered by?
A
Mediastinal pleura
9
Q
Position of thoracic duct in regards to esophagus in posterior mediastinum?
A
- Inferior portion: right side - Superior portion: left side
10
Q
Position of aorta in regards to esophagus in posterior mediastinum?
A
Left
11
Q
Position of right pulmonary artery and left main bronchus in regards to esophagus in posterior mediastinum?
A
Anterior
12
Q
4 structures that are posterior to the esophagus at some point in the posterior mediastinum?
A
- Thoracic duct2. Hemiazygos veins3. Right posterior intercostal vessels4. Thoracic aorta (near diaphragm)
13
Q
At what 4 locations can the esophagus be compresses/narrowed? What is at higher risk at these locations?
A
- Junction of esophagus and pharynx in the neck2. Aortic arch crossing over the esophagus in superior mediastinum3. Left main bronchus crossing over the esophagus in posterior mediastinum4. At esophageal hiatus in posterior mediastinum Higher risk of swallowed objects getting lodged at these locations and if the object is corrosive it would cause more damage at these locations
14
Q
What arteries do esophageal arteries arise from?
A
- Thoracic aorta2. Bronchial arteries3. Ascending branches of left gastric artery in abdomen 4. Inferior thyroid artery
15
Q
What veins do esophageal veins drain into?
A
- Azygos vein2. Hemiazygos vein3. Left gastric vein in abdomen
16
Q
Lymphatic drainage of esophagus in posterior mediastinum?
A
- Posterior mediastinal lymph nodes2. Left gastric lymph nodes (inferior 1/3rd)
17
Q
Innervation of esophagus?
A
Branches from vagus nerves and sympathetic trunks
18
Q
Innervation of striated muscle in superior portion of the esophagus?
A
Branchial efferents from vagus nerves
19
Q
Innervation of smooth muscle fibers in inferior portion of the esophagus?
A
Preganglionic fibers that are parasympathetic visceral efferents and synapse in the myenteric and submucosal plexuses of the enteric NS in the esophageal wall
20
Q
Sensory innervation of esophagus? Which ones are responsible for transmitting pain information to the CNS?
A
Visceral afferents in :1. Vagus nerves2. Sympathetic trunks3. Splanchnic nerves
21
Q
Are the visceral afferents from the vagus nerves involved in the relay of pain recognition?
A
NOPE
22
Q
What are the 2 trunks formed by the esophageal plexus?
A
Trunks formed by the esophageal plexus just above the diaphragm:1. Anterior vagal trunk on anterior surface of esophagus mainly from fibers from left vagus nerve2. Posterior vagal trunk on posterior surface of esophagus mainly from fibers from right vagus nerveThese continue through the diaphragm
23
Q
To which lymph nodes does esophageal cancer spread?
A
- Lymph nodes in neck2. Lymph nodes around celiac artery
24
Q
Technique to assess site of esophageal cancer?
A
Endoscopy or barium swallow
25
Survival rate of esophageal rupture caught early? Untreated?
Caught early: 65%Untreated: 0%
26
Where do esophageal ruptures occur typically? Treatment?
Lower third of esophagus on the left Treatment: urgent surgical repair
27
Consequences of esophageal rupture?
1. Sudden rise in intraluminal esophageal pressure produced by vomiting2. Uncoordination and failure of cricopharyngeus muscle to relax3. Large left pleural effusion that contains the gastric contents 4. Subcutaneous emphysema (air gets into tissues under the skin)
28
Which lung is in contact with the esophagus?
Right lung
29
Vertebral levels of thoracic aorta?
T4 to T12
30
Pathway of thoracic aorta?
Left of midline => approaches midline and directly anterior to vertebrae inferiorly => aortic hiatus through diaphragm
31
7 branches of the thoracic aorta?
1. Pericardial2. Bronchial3. Esophageal4. Mediastinal5. Posterior intercostal6. Superior phrenic7. Subcostal
32
What is the azygos system of veins?
Series of longitudinal vessels on each side of the body that drain blood from the body wall and move it superiorly to drain into SVC (but blood from viscera may also enter them)
33
Where are anastomoses found with the azygos system of veins?
With abdominal veins
34
Are the azygos veins connected from side to side?
YUP
35
What happens if the IVC is blocked?
Azygos system of veins will serve as an anastomotic pathway capable of returning blood from lower part of body to the heart
36
3 major veins of azygos system of veins?
1. Azygos vein on right2. Hemiazygos vein on left3. Accessory hemiazygos vein on left
37
Pathway of azygos vein?
Arises in abdomen opposite L1 or L2 at junction between right ascending lumbar vein and right subcostal vein OR from IVC => aortic hiatus => posterior mediastinum to the right of the thoracic duct => arches anteriorly at T4 over root of right lung and right vagus nerve to drain into IVC before it enters pericardial sac
38
8 tributaries to azygos vein?
1. Right superior intercostal vein2. 5th to 11th right posterior intercostal veins 3. Hemiazygos vein4. Accessory hemiazygos vein5. Esophageal veins6. Mediastinal veins7. Pericardial veins8. Right bronchial veins
39
What is the superior intercostal vein formed by?
Junction of 2nd, 3rd, and 4th intercostal veins
40
Other name for hemiazygos vein?
Inferior hemiazygos vein
41
Pathway of hemiazygos vein?
Arises at junction between left ascending lumbar vein and left subcostal vein in abdomen (or either of those alone) => aortic hiatus => posterior mediastinum to left of thoracic duct to T9 => crosses vertebral column posterior to thoracic aorta, esophagus, and thoracic duct to enter azygos vein
42
3 tributaries to hemiazygos vein?
1. Lowest 4 or 5 left posterior intercostal veins2. Esophageal veins3. Mediastinal veins
43
Pathway of accessory hemiazygos vein?
Descends from superior portion of posterior mediastinum on left side => crosses vertebral column at T8 to join azygos vein OR ends in hemiazygos vein OR connects to both
44
Other name for accessory hemiazygos vein?
Superior hemiazygos vein
45
To what does the accessory hemiazygos vein connect to sometimes superiorly?
Left superior intercostal vein
46
2 tributaries to accessory hemiazygos vein?
1. 4th to 8th left posterior intercostal veins2. Left bronchial veins (sometimes)
47
Which vein of the azygos system of veins often has a connection to the left renal vein?
Hemiazygos vein
48
Pathway of thoracic duct?
Confluence of lymph trunks in abdomen forming a saccular dilation called the cisterna chyli => enters thorax posterior to aorta through aortic hiatus => posterior mediastinum to the right of midline between thoracic aorta and azygos vein and posterior to esophagus and anterior to vertebrae => moves to left of midline at T5 and enters superior mediastinum => through superior mediastinum => neck => left jugular trunk and left subclavian trunk (draining left neck/head and left upper limb) join the thoracic duct => empties into junction of left subclavian and left internal jugular veins
49
Other name for cisterna chyli?
Chyle cistern
50
What does the cisterny chyli drain?
1. Abdominal viscera and walls2. Pelvis3. Perineum 4. Lower limbs
51
Vertebral level of thoracic duct?
L2 to root of neck
52
5 tributaries to thoracic duct?
1. Lymph trunks in abdomen2. Descending thoracic lymph trunks draining lower 6 or 7 intercostal spaces on both sides3. Upper intercostal lymph trunks draining upper LEFT 5 or 6 intercostal spaces4. Ducts from posterior mediastinal nodes5. Ducts from posterior diaphragmatic nodes
53
Describe the sympathetic trunks of the posterior mediastinum.
2 parallel cords with 11 or 12 ganglia connected to adjacent thoracic spinal nerves by white and gray rami communicans
54
How are sympathetic trunks numbered?
According to the thoracic spinal nerve with which they are associated
55
Position of sympathetic trunks in superior portion of posterior mediastinum?
Anterior to neck of the ribs
56
Position of sympathetic trunks in inferior portion of posterior mediastinum?
More medial than in superior portion of posterior mediastinum anterior to the lateral aspects of vertebral bodies
57
How do the sympathetic trunks leave the thorax?
Pass posterior to the diaphragm under the median arcuate ligament OR through crura of diaphragm
58
What are the sympathetic trunks covered by in the thorax?
Parietal pleura
59
What are the 2 types of medial branches given off by the ganglia of the sympathetic trunks?
1. Branches from upper 5 ganglia: postganglionic sympathetic fibers supplying thoracic viscera (small and contain visceral afferents)2. Branches from lower 7 ganglia: preganglionic sympathetic fibers supplying abdominal and pelvic viscera (large and contain visceral afferents) => forming the greater, lesser, and least splanchnic nerves
60
Describe the pathway of the greater splanchnic nerve.
5th to 9th/10th thoracic ganglia => crus of diaphragm to abdomen => ends in celiac ganglion
61
Describe the pathway of the lesser splanchnic nerve.
9th and 10th OR 10th and 11th thoracic ganglia => crus of diaphragm to abdomen => ends in aorticorenal ganglion
62
Describe the pathway of the least splanchnic nerve.
12th thoracic ganglion => crus of diaphragm to abdomen => ends in renal plexus
63
What is the crus of the diaphragm?
Refers to one of two (R and L) tendinous structures that extends below the diaphragm to the vertebral column
64
Boundaries of anterior mediastinum?
1. Superiorly: sternal angle2. Inferiorly: diaphragm3. Laterally: mediastinal pleura4. Anteriorly: sternum5. Posteriorly: middle mediastinum
65
What is the major structure of the anterior mediastinum? Other contents?
Portion of the thymus Other contents: 1. Fat2. Connective tissue3. Lymph nodes4. Mediastinal branches of internal thoracic vessels5. Sternopericardial ligaments
66
What kind of thoracic splanchnic innervates the adrenal glands?
Greater thoracic splanchnic
67
Location of sympathetic trunks with regards to the intercostal arteries and veins?
Superficial to
68
Can you find all 3 thoracic splanchnic in a cadaver?
Usually only greater, sometimes lesser, never the least
69
Only part of posterior mediastinum that lymphatically drains to abdomen?
Inferior 1/3rd of esophagus
70
What do we call the vagus nerves right before they become the anterior and posterior trunks on the esophagus?
Right and left vagal trunks
71
What is the most posterior structure of the posterior mediastinum?
Thoracic duct
72
What do we call the hole through which the IVC penetrates the diaphragm? Vertebral level?
Caval opening: T8
73
What is dysphagia?
Difficulty swallowing
74
Do intercostal nerves carry mainly myelinated neurons? Explain.
YUPThey carry:1. Somatic motor innervation to muscles of thoracic wall2. Somatic sensory innervation from skin and parietal pleura3. Postganglionic sympathetic fibers to periphery
75
Are intercostal nerves protected by the inferior borders of the ribs?
YUP
76
Where do the bronchial arteries branch from?
Thoracic aorta
77
What does the greater splanchnic innervate?
Foregut and adrenal medulla
78
What does the lesser splanchnic innervate?
1. Midgut2. Kidneys and upper ureters
79
What does the least splanchnic innervate?
Renal plexus, which enters the kidneys on arterial branches to supply the vessels, Renal glomerulus, and tubules with branches to the ureteric plexus, the spermatic plexus and, on the right side, to the inferior vena cavaThe ovarian plexus arises from the renal plexus, and is one of two sympathetic supplies distributed to the ovary and fundus of the uterus
80
7 structures of the adult foregut?
1. Esophagus (distal end)2. Stomach3. Duodenum (proximal half)4. Liver5. Gallbladder6. Pancreas7. Spleen
81
8 structures of the adult midgut?
1. Duodenum (distal half)2. Jejunum3. Ileum4. Cecum5. Appendix6. Ascending colon7. Hepatic flexure of colon8. Transverse colon (proximal two-thirds)
82
5 structures of the adult hindgut?
1. Distal third of the transverse colon 2. Splenic flexure of colon3. Descending colon4. Sigmoid colon 5. Rectum
83
5 components of middle inferior mediastinum?
1. Pericardium2. Heart3. Roots of great vessels4. Arch of the azygos vein5. Main bronchii
84
Are all 11 physiological systems found in the mediastinum?
YUP
85
What are esophageal varicosities? Most common cause? Why are these potentially lethal?
Enlarged esophageal veins associated with chronic alcoholism Potentially lethal because they can burst causing severe hemorrhage
86
Are the sympathetic trunks technically in the posterior mediastinum?
NOPE, because they are not between the R and L pleural cavities
87
What kind of nerve fibers does the phrenic nerve carry?
Motor, sensory, and sympathetic nerve fibers
88
Why does esophageal cancer cause anemia?
Tumors of the GIT are very friable and with the passage of digested material across the tumor, low-grade bleeding occurs causing anemia (usually asymptomatic)
89
Describe the surgical procedure of esophageal resection to treat cancer. What is this called?
Transthoracic esophagectomy:1. Patient is placed in supine position 2. Laparotomy (surgical incision of abdomen) to assess evidence of disease in abdominal cavity3. Stomach is mobilized with preservation of right gastric and gastro-omental arteries4. Short gastric vessels and left gastric vessels are divided5. Pyloromyotomy is performed (incision in stomach on the pylorus, the furthest part of the stomach that connects to the duodenum)6. Abdominal wound is closed7. Patient is placed in left lateral position 8. Right posterolateral thoracotomy is performed through 5TH INTERCOSTAL SPACE9. Azygos vein divided to provide full access to the whole length of the esophagus 10. Stomach is delivered through the diaphragmatic hiatus 11. Esophagus is resected and stomach is anastomosed to the cervical esophagus
90
How does esophageal cancer spread?
Submucosa or locoregional lymph nodes
91
When are most esophageal cancers diagnosed? Survival rate?
LateSurvival rate: 25% 5-year survival rate
92
Position of superior poles of kidneys?
Right: Anterior to rib 12 Left: Anterior to ribs 11 and 12
93
What is the thoracic wall made of?
Posteriorly: 12 thoracic vertebraeLaterally: 12 ribs + ICS muscles Anteriorly: sternum
94
T1 dermatome?
Medial forearm
95
T2 dermatome?
Medial arm + 2nd ICS
96
Sensory innervation of anterosuperior portion of the trunk?
Anterior ramus of C4 via supraclavicular branches of cervical plexus
97
Dermatome over xiphoid process?
T6
98
Dermatome over nipples?
T4
99
Describe dermatomes T7 to T12.
They follow the contour of the ribs onto the anterior abdominal wall
100
Dermatome of umbilicus?
T10
101
Dermatomes of costal margin?
T5 to T9
