Dissection of the Posterior Mediastinum Flashcards
Boundaries of posterior mediastinum?
- Superiorly: sternal angle
- Inferiorly: diaphragm
- Laterally: mediastinal pleura
- Anteriorly: pericardial sac
6 major structures of the posterior mediastinum?
- Esophagus with its plexus (right and left)
- Thoracic aorta with its branches
- Azygos system of veins
- Thoracic duct and associated lymph nodes
- Sympathetic trunks
- Thoracic splanchnic nerves
Vertebral borders of esophagus?
C6 to T11
What is the esophagus?
Muscular tube
Pathway of esophagus in posterior mediastinum?
Anterior aspect of vertebrae in midline => anterior and to the left to be anterior to the thoracic aorta to enter the diaphragm
Vertebral level of esophagus passing through esophageal hiatus to enter diaphragm?
T10
Esophagus 2 attachments?
- Pharynx
2. Diaphragm
What is the right side of the esophagus covered by?
Mediastinal pleura
Position of thoracic duct in regards to esophagus in posterior mediastinum?
- Inferior portion: right side
- Superior portion: left side
Position of aorta in regards to esophagus in posterior mediastinum?
Left
Position of right pulmonary artery and left main bronchus in regards to esophagus in posterior mediastinum?
Anterior
4 structures that are posterior to the esophagus at some point in the posterior mediastinum?
- Thoracic duct
- Hemiazygos veins
- Right posterior intercostal vessels
- Thoracic aorta (near diaphragm)
At what 4 locations can the esophagus be compresses/narrowed? What is at higher risk at these locations?
- Junction of esophagus and pharynx in the neck
- Aortic arch crossing over the esophagus in superior mediastinum
- Left main bronchus crossing over the esophagus in posterior mediastinum
- 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
What arteries do esophageal arteries arise from?
- Thoracic aorta
- Bronchial arteries
- Ascending branches of left gastric artery in abdomen
- Inferior thyroid artery
What veins do esophageal veins drain into?
- Azygos vein
- Hemiazygos vein
- Left gastric vein in abdomen
Lymphatic drainage of esophagus in posterior mediastinum?
- Posterior mediastinal lymph nodes
2. Left gastric lymph nodes (inferior 1/3rd)
Innervation of esophagus?
Branches from vagus nerves and sympathetic trunks
Innervation of striated muscle in superior portion of the esophagus?
Branchial efferents from vagus nerves
Innervation of smooth muscle fibers in inferior portion of the esophagus?
Preganglionic fibers that are parasympathetic visceral efferents and synapse in the myenteric and submucosal plexuses of the enteric NS in the esophageal wall
Sensory innervation of esophagus? Which ones are responsible for transmitting pain information to the CNS?
Visceral afferents in :
- Vagus nerves
- Sympathetic trunks***
- Splanchnic nerves***
Are the visceral afferents from the vagus nerves involved in the relay of pain recognition?
NOPE
What are the 2 trunks formed by the esophageal plexus?
Trunks formed by the esophageal plexus just above the diaphragm:
- Anterior vagal trunk on anterior surface of esophagus mainly from fibers from left vagus nerve
- Posterior vagal trunk on posterior surface of esophagus mainly from fibers from right vagus nerve
These continue through the diaphragm
To which lymph nodes does esophageal cancer spread?
- Lymph nodes in neck
2. Lymph nodes around celiac artery
Technique to assess site of esophageal cancer?
Endoscopy or barium swallow
Survival rate of esophageal rupture caught early? Untreated?
Caught early: 65%
Untreated: 0%
Where do esophageal ruptures occur typically? Treatment?
Lower third of esophagus on the left
Treatment: urgent surgical repair
Consequences of esophageal rupture?
- Sudden rise in intraluminal esophageal pressure produced by vomiting
- Uncoordination and failure of cricopharyngeus muscle to relax
- Large left pleural effusion that contains the gastric contents
- Subcutaneous emphysema (air gets into tissues under the skin)
Which lung is in contact with the esophagus?
Right lung
Vertebral levels of thoracic aorta?
T4 to T12
Pathway of thoracic aorta?
Left of midline => approaches midline and directly anterior to vertebrae inferiorly => aortic hiatus through diaphragm
7 branches of the thoracic aorta?
- Pericardial
- Bronchial
- Esophageal
- Mediastinal
- Posterior intercostal
- Superior phrenic
- Subcostal
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)
Where are anastomoses found with the azygos system of veins?
With abdominal veins
Are the azygos veins connected from side to side?
YUP
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
3 major veins of azygos system of veins?
- Azygos vein on right
- Hemiazygos vein on left
- Accessory hemiazygos vein on left
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
8 tributaries to azygos vein?
- Right superior intercostal vein
- 5th to 11th right posterior intercostal veins
- Hemiazygos vein
- Accessory hemiazygos vein
- Esophageal veins
- Mediastinal veins
- Pericardial veins
- Right bronchial veins
What is the superior intercostal vein formed by?
Junction of 2nd, 3rd, and 4th intercostal veins
Other name for hemiazygos vein?
Inferior hemiazygos vein