posterior mediastinum

Question 1

what is the anterior boundary of the posterior mediastinum?

Answer 1

posterior pericardium

Question 2

what is the posterior boundary of the posterior mediastinum?

Answer 2

vertebrae T5-12

Question 3

what is the lateral boundary of the posterior mediastinum?

Answer 3

mediastinal pleura

Question 4

what is the superior boundary of the posterior mediastinum?

Answer 4

transverse throacic plane

Question 5

what is the inferior boundary of the posterior mediastinum?

Answer 5

diaphragm

Question 6

what is contained in the posterior mediastinum?

Answer 6

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

Question 7

what is the flow of the sympathetic nervous system?

Answer 7

thoracolumbar outflow T1 to L2

Question 8

what is the flow of the parasympathetic nervous system?

Answer 8

craniosacral outflow - some cranial nerves (including vagus nerve), S2, S3 and S4

Question 9

what is the sympathetic trunk?

Answer 9

vertical chain of sympathetic nerves running the entire length of the vertebral column

Question 10

where is the sympathetic trunk located?

Answer 10

both sides of vertebral bodies and the paravertebral ganglia is located along its length

Question 11

in the thoracic spine how many ganglia are there per spinal level?

Answer 11

one ganglion per spinal level

Question 12

what happens at spinal nerve levels T1-T4/5?

Answer 12

• preganglionic sympathetic fibres leave the spinal nerve (white rami communicates) and synapse at paravertebral ganglion
• postganglionic sympathetic fibres leave the ganglion (grey rami communicates) and pass to the pulmonary, cardiac and oesophageal plexi
• these nerves can also carry afferent fibres (carrying sensroy information) from the thoracic viscera they supply back to the brain

Question 13

what is a dermatome?

Answer 13

an area of skin supplied by a single spinal cord level or spinal nerve

Question 14

where is pain from the heart felt?

Answer 14

down arm and across chest (T1-T4/5)

Question 15

what nerve supplies to the diaphragm?

Answer 15

phrenic nerve C3, C4 and C5

Question 16

where can referred pain from the diaphragm be felt?

Answer 16

shoulder

Question 17

what happens at spinal nerve levels T5/6-T12?

Answer 17

• preganglionic sympathetic fibres leave the spinal cord (white rami communicates) and enter the ganglion but don’t synapse
• hence, preganglionic sympathetic fibres leave these ganglia and synapse in the paravertebral (pre-aortic) ganglia before passing to the abdominal viscera
• there form the 3 splanchnic nerves

Question 18

where do the greater splanchnic nerves arise from?

Answer 18

levels T5-9

Question 19

where do the lesser splanchnic nerves arise from?

Answer 19

levels T10-11

Question 20

where do the least splanchnic nerves arise from?

Answer 20

levels T12

Question 21

generally where do splanchnic nerves travel?

Answer 21

descend medially from ganglia across the vertebral bodies and enter the abdomen by piercing the diaphragm

Question 22

what do splanchnic do?

Answer 22

carry preganglionic sympathetic fibres to and visceral afferent fibres from the abdominal viscera

Question 23

where does the vagus nerve enter?

Answer 23

• enters superior mediastinum posterior to the sternoclavicular joint
• the left and right recurrent laryngeal nerves branch from it but have differing courses
• continues into posterior mediastinum to contribute to pulmonary, cardiac and oesophageal plexues

Question 24

what type of supply is the vagus nerve?

Answer 24

parasympathetic supply

Question 25

where does the right vagus nerve travel?

Answer 25

- right recurrent laryngeal branch hooks under right subclavian artery and ascends between trachea and oesophagus - right vagus continues posterior to the right of the trachea, posterior to right brachiocephalic vein and lung root/hilum

Question 26

what does the right vagus supply?

Answer 26

the larynx

Question 27

where does the left vagus nerve travel?

Answer 27

- left recurrent laryngeal nerve hooks inferiorly to the aortic arch, immediately lateral to ligamentum arteriosum - rest of the left vagus runs posteriorly to lung root

Question 28

what does the left vagus supply?

Answer 28

the larynx

Question 29

where does the thoracic aorta travel?

Answer 29

- continues with arch or aorta - descend on the left side of the vertrbae T5-12 - oesophagus positioned to its right - terminates at vertebral level T12 where it enters the abdomen through the aortic hiatus in the diaphragm - thoracic duct and azygous veins ascend on its right hand side and also pass through diaphragm at the aortic hiatus

Question 30

what are the paired branches of the thoracic aorta?

Answer 30

1) posterior intercostal 2) subcostal 3) bronchial 4) superior phrenic

Question 31

what are the unpaired branches of the thoracic aorta?

Answer 31

1) pericardial 2) oesophageal 3) mediastinal

Question 32

where does the azygos vein travel?

Answer 32

- arises on the right side by junction of subcostal (T12) level and ascending lumbar veins - arches over root of right lung to join SVC

Question 33

what does the azygos vein do?

Answer 33

- it drains deoxygenated blood from the posterior thoraco-abdominal walls and viscera - usually receives blood form the Hemiazygous veins which drains the left side - forms a collateral pathway between the SVC and IVC

Question 34

what are the tributaries of the azygos vein?

Answer 34

posterior intercostal veins (level T5-T11), bronchial veins, vertebral venous plexus

Question 35

where does the hemi-azygous vein travel?

Answer 35

- arises on the left side by the junction of subcostal (T12 level) and ascending lumbar veins - ascends on the left side posterior to aorta draining left posterior intercostal veins level T9-11 - crosses T7/8 to joint azygos and sometimes joins hemi-azygos

Question 36

what does the hemi-azygos vein do?

Answer 36

- corsses to right and joins azygos vein | - accessory hemi-azygos drains levels T5-T8 on left side

Question 37

what is the thoracic duct?

Answer 37

the largest lymph channel

Question 38

what does the thoracic duct do?

Answer 38

conveys all lymph from body except head, neck, upper limb and throat on right side

Question 39

where does the thoracic duct originate?

Answer 39

Cisterna Chyli in abdomen (L2)

Question 40

where does the thoracic duct travel?

Answer 40

- ascends through aortic hiatus passing anterior to thoracic vertebrae - ascends into superior mediastinum and drains into venous system at the left venous angle (junction of internal jugular and subclavian veins)

Question 41

where does the oesophagus travel?

Answer 41

- descends from superior mediastinum posterior to the trachea - passes posterior and to the right of aorta - veers slightly left before piercing through the diaphragm - becomes anterior to abdominal aorta before entering the stomach

Question 42

what is the innervation of the oesophagus?

Answer 42

CNX and sympathetic trunk via oesophageal plexus

Question 43

what is the oesophagus?

Answer 43

a muscular tube

Question 44

where are the 3 constrictions of the aorta?

Answer 44

1) arch of aorta 2) left main bronchus 3) diaphragm