Posterior Mediastinum and the Neck

Question 1

Where is the carina?

Answer 1

where trachea bifurcates at level of T4/5 vertebrae

Question 2

Where is the posterior mediastinum?

Answer 2

vertically it runs from the diaphragm to the line that connects the sternal angle with T4/5 junction posteriorly. Section posterior to the heart and pericardium.

Question 3

What structures are in the posterior mediastinum?

Answer 3

• Descending (thoracic) aorta
• azygos veins
• oesophagus
• thoracic duct
• sympathetic trunk + splanchnic nerves
• posterior intercostal vessels and nerves

Question 4

What branches does the descending (thoracic) aorta give rise to in the posterior mediastinum?

Answer 4

• posterior intercostal arteries (supply intercostal spaces)
• bronchial arteries (lungs)
• oesophageal branches
• pericardial branches (pericardium)
• phrenic branches (diaphragm)

Question 5

At what level does the aorta pass through the diaphragm?

Answer 5

T12

Question 6

Where does the azygos system of veins arise from?

Answer 6

the abdomen at level L1/L2. Goes into posterior mediastinum through diaphragm.

Question 7

What does azygos system do? (where does it drain blood from)

Answer 7

Drains blood from posterior thoracic wall
Returns it to superior vena cava
Receives blood from…
posterior intercostal veins
Oesophageal veins
Bronchial veins

Question 8

Describe the position of the oesophagus in the posterior mediastinum

Answer 8

lies right of the aorta
supplied by oesophagal arteries from descending aorta
oesophagal veins return to azygos
passes trhough the oesophageal hiatus in the diaphragm at level T10

Question 9

What and where is the thoracic duct

Answer 9

Begins at the cisterna chyli and ascends into the thorax, into the neck
Terminates at opening into the venous system at junction of left internal jugular vein and left subclavian vein
Doesn’t drain the right upper limb

Question 10

Where does the thoracic duct collect lymph from?

Answer 10

Cisterna chyri (collects from lower limbs, pelvis, abdomen)
In thorax, from intercostal spaces and lymph nodes
Left side of head and neck and left upper limb

Question 11

What drains right side of head and upper limb of lymph?

Answer 11

lymphatic ducts that enter the venous system at the junction of the right subclavian vein and right internal jugular veins

Question 12

Describe the position of the sympathetic trunk/s

Answer 12

they lie on the posterior thoracic wall
posterior to the parietal pleura
either side of the vertebral column
extends from the skull base to the coccyx

Question 13

Describe the sympathetic trunks

Answer 13

thin, longitudinal fibre tracks
regularly interspersed with ganglia
sometimes referred to as paravertebral ganglia, as they run parallel to the vertebral column

Question 14

What is the purpose of the sympathetic trunk?

Answer 14

Allows sympathetic fibres (from T1-L2/3) to reach all parts of the body

Question 15

How do preganglionic sympathetic fibres enter the sympathetic trunk?

Answer 15

Nerve fibres exit vertebral column at T1-L2/3
Separate from spinal nerves and enter trunk (via connecting branch - white ramus communicans)
In the trunk, it can…
- synapse in the ganglion at entry level
- ascend/descend in trunk before synapsing at a ganglion
- travel through the ganglion and trunk without synapsing

Question 16

3 things preganglionic sympathetic fibres can do once they enter the sympathetic trunk

Answer 16

• synapse in the ganglion at entry level
• ascend/descend in trunk before synapsing at a ganglion
• travel through the ganglion and trunk without synapsing

Question 17

When the preganglionic sympathetic fibres synapse with a ganglion in the sympathetic trunk either at entry or after ascending/descending…
…how do the postganglionic axons leave the ganglia?

Answer 17

• enter spinal nerves by connecting branch (grey ramus communications)
• form visceral nerves that convey sympathetic fibres to the head
• form visceral nerves that convey sympathetic fibres to the thoracic viscera
  (cardiopulmonary splanchic nerves)

Question 18

What is white ramus communications?

Answer 18

A short connecting branch allowing preganglionic nerves to enter the sympathetic trunk

Question 19

What is grey ramus communications?

Answer 19

A short connecting branch that allows postganglionic axons to enter spinal nerves

Question 20

What are the 4 abdominopelvic splanchnic nerves?

Answer 20

Greater splanchnic nerve (preganglionic fibres originate from T5-T9)
Lesser splanchnic nerve (T10-T11)
Least splanchnic nerve (T12)
Lumbar splanchnic nerve (L1-L2)

Question 21

Which splanchnic nerves are formed in the posterior mediastinum?

Answer 21

The greater, lesser and least abdominopelvic splanchnic nerves
They traverse the diaphragm to enter abdomen
Ultimately synapse with prevertebral ganglia

Question 22

What do the posterior intercostal spaces contain?

Answer 22

Intercostal muscles
A posterior intercostal artery (branch of thoracic)
A posterior intercostal vein (drains to azygos system)
A posterior intercostal nerve

Question 23

What fibres do cardiopulmonary splanchnic nerves convey to thoracic viscera?

Answer 23

Postganglionic sympathetic fibres.

Question 24

What fibres does the vagus nerve convey to thoracic viscera?

Answer 24

parasympathetic fibres

Question 25

What are autonomic nerve plexuses?

Answer 25

They look like fine meshes or webs
Can contain parasympathetic and sympathetic fibres

Question 26

What are the 3 autonomic nerve plexuses in the thorax?

Answer 26

Cardiac plexus
Pulmonary plexus
Oesophageal plexus

Question 27

What does the cardiac plexus (sympathetic fibres from T1-T5 nerves) innervate?

Answer 27

Sinoatrial node of heart
Sympathetic - increase heart rate and force of contraction
Parasympathetic - decrease “ “

Question 28

What does the pulmonary plexus innervate?

Answer 28

The bronchi
Sympathetic - relaxes the bronchi
Parasympathetic - constricts the bronchi

Question 29

What does the oesophageal plexus innervate?

Answer 29

Overlies anterior surface of oesophagus
Sympathetic - inhibit peristalsis
Parasympathetic - stimulate peristalsis

Question 30

What do visceral afferents do?

Answer 30

Relay sensory information from thoracic viscera back to the CNS via vagus and thoracic splanchnic nerves

Question 31

What is referred pain? e.g. cardiac referred pain

Answer 31

Pain from one part of the body is felt in another region e.g. cardiac pain felt in central chest, left neck, left arm

Question 32

How is the heart innervated?

Answer 32

Cardiac plexus (sympathetic fibres from T1-T5 on spine, contains parasympathetic)
Visceral sensory nerves (convey sensory info back to CNS)(enters at T1-T5 alongside sympathetic fibres)

Question 33

What sensory information is returned to the spinal segments T1-T5?

Answer 33

• visceral sensory information from the heart
• somatic sensory information from skin of chest wall, neck and arm
• this is why brain interprets cardiac pain as pain from chest neck and arm

Question 34

When does sensation of visceral sensory nerves of the heart reach our conscious perception?

Answer 34

Only when the heart is ischaemic - interpreted as pain, tightness, crushing pressure or burning that may be severe

Question 35

What is an aortic dissection?

Answer 35

Longitudinal tear in aortic wall
Allows blood to collect between intima and media
Occurs in ascending, arch of, or descending aorta
Presents with sudden onset severe chest pain and/or back pain

Question 36

What is Horner’s syndrome? (3 signs together)

Answer 36

3 signs:
- small pupil (miosis)
- drooping upper eyelid (ptosis)
- lack of sweating (anhidrosis)
ON ONE SIDE OF TH FACE

Caused by interruption to sympathetic nerves innervating the head
e.g. cancer in apex of lung invading sympathetic chain

Question 37

What is a hiatus hernia?

Answer 37

When the abdominal segment of the oesophagus and part of the stomach moves proximally through oesophageal opening in diaphragm

Symptoms such as heartburn or reflux