Phrenic and Vagus nerve

Question 1

Phrenic nerve

Answer 1

• Originates from cervical plexus
• C3-C5
• Provide motor, sensory and sympathetic innervation to diaphragm
• Gives off branches to mediastinal, diaphragmatic pleura and pericardium

Question 2

Right phrenic nerve Course

Answer 2

1) Descends lateral to internal jugular vein
2) Passes anterior to subclavian artery but posterior to subclavian vein
3) Passes lateral to right brachiocephalic vein and SVC
4) Passes ANTERIOR to hilum of right lung
5) Crosses over pericardium to reach the diaphragm

Question 3

Left phrenic nerve Course

Answer 3

1) Descends lateral to left subclavian artery
2) Crosses superficially over left vagus nerve at aortic arch
3) Crosses ANTERIORLY to hilum of left lung
4) Crosses over pericardium to reach diaphragm

Question 4

Vagus nerve (CN X)

Answer 4

• Provides parasympathetic innervation to heart and visceral organs (until proximal 2/3 of transverse colon)
• Supplies skeletal muscles:
  1) Superior, middle and inferior pharyngeal constrictors
  2) Muscles of larynx (via recurrent laryngeal nerve)
• Lies within carotid sheath at the neck (with internal jugular vein and common carotid artery)
• Gives off cardiac, oesophageal and pulmonary plexuses

Question 5

Right vagus nerve Course

Answer 5

1) Passes anterior to right subclavian artery, giving rise to the right recurrent laryngeal artery (hooks underneath the right subclavian artery to ascend up towards larynx)
2) Passes POSTERIOR to hilum of right lung
3) Continues as posterior vagal trunk, descending along oesophagus

Question 6

Left vagus nerve Course

Answer 6

1) Descends between the left common carotid and left subclavian arteries
2) Crosses to the left of aortic arch, and crossed by the phrenic nerve anteriorly
3) Gives rise to the left recurrent laryngeal nerve, hooking around the arch of aorta (near the ligamentum arteriosum) to ascend in the groove between the trachea and oesophagus to the larynx
4) Descends along oesophagus as the anterior vagal trunk