Lecture 4: Posterior Mediastinum

Question 1

what are the boundaries of the posterior mediastinum

Answer 1

anterior: posterior pericardium
posterior: vertebrae T5-12
lateral: mediastinal pleura
superior: transverse thoracic plane
inferior: diaphragm

Question 2

what are the contents of the posterior mediastinum

Answer 2

• oesophagus
• thoracic aorta
• azygos system of veins
• thoracic duct
• vagus nerve
• sympathetic trunk
• splanchnic nerves

Question 3

where is the sympathetic nervous system located

Answer 3

• thoracolumbar outflow

- T1 to L2

Question 4

where is the parasympathetic nervous system located

Answer 4

• craniosacral outflow
• some cranial nerves including vagus nerve
• S2, 3 and 4

Question 5

where do the thoracic viscera receive sympathetic supply from

Answer 5

sympathetic trunk from T1-T4/5

Question 6

where can referred pain from the heart be felt

Answer 6

down arm and across chest

Question 7

where can referred pain from the diaphragm be felt

Answer 7

across the chest

Question 8

where does the parasympathetic supply to the thoracic viscera come from

Answer 8

vagus nerve

Question 9

what are the levels of splanchnic nerves

Answer 9

greater: T5-T9
lesser: T10-T11
least: T12

Question 10

where does the thoracic aorta descend

Answer 10

• left side of vertebrae T5-T12

- pierces diaphragm at T12, where it enters the diaphragm through aortic hiatus

Question 11

branches of the thoracic aorta

Answer 11

paired:
- posterior intercostal
- subcostal
- bronchial
- superior phrenic
unpaired:
- pericardial
- oesophageal
- mediastinal

Question 12

where does the azygous vein originate from and what does it drain (right side)

Answer 12

• originates from union of ascending lumbar vein and subcostal vein
• drains blood from T5 - T11 posterior intercostal veins
• then arches over root of right lung where it meets superior vena cava

Question 13

where does the azygous vein originate from and what does it drain (left side)

Answer 13

• originates from union of ascending lumbar vein and subcostal vein
• drains blood from T5 - T8 posterior intercostal veins through accessory hemi-azygous vein
• drains blood from T9 - T11 posterior intercostal veins through hemi-azygous vein

Question 14

what is the evolutionary benefit of the azygous system

Answer 14

allows collateral circulation of venous blood through superior and inferior vena cava

Question 15

where does the thoracic duct originate and end

Answer 15

• originates in cisterna chyli in abdomen (L2)

- ascends into superior mediastinum and drains into left venous angle

Question 16

what is the left venous angle

Answer 16

junction of internal jugular and subclavian veins

Question 17

what does the thoracic duct drain from

Answer 17

everywhere but:

• head
• neck
• right upper limb and right thorax

Question 18

where does the oesophagus run in relation to the aorta

Answer 18

• posterior and to the right

- veers slightly left before piercing through diaphragm

Question 19

where are the 3 constrictions of the oesophagus

Answer 19

• arch of aorta
• left main bronchus
• diaphragm