topic 24/ vagus & phrenic nerves

Question 1

vagus nerve

Answer 1

course:
-originates from medulla of brainstem , exits via jugular foramen (with glossopharyngeal & accessory nerves)
travel in carotid sheath with internal jugular vein & common carotid artery
in thoracuc cavity enter sup. mediastinum post. to sternockavicular joint
2 branches: Righ: ant. to subclavian - give right recuurent laryngeal - loops around right subclavian - ascends to larynx - continue to post. to root of right lung
Left: crosses aortic arch - gives left recurrent - loops under aortic arch (near ligamentum arteriosum) - accends to larynx - to post. of root of left lung

Thoracic branches:
*cardiac
*pulmonary
*esophageal

Terminal branches:
near diaphragrm, forms ant. & post vagal trrunks - go to abdomen

Question 2

function of vagus nerve

Answer 2

• parasymphatetic innervation: heart rate, sweating, muscle movements in mouth like during speech via reccurent laryngeal
  *motor: muscles of pharynx, larynx & soft palate
  *sensory: thoracic & abdominal viscera

Question 3

course of phrenic nerve

Answer 3

Origin: ant. rami of cervical plexus (C3 TO C5)

Neck: The phrenic nerve descends obliquely with the internal jugular vein across the anterior scalene muscle.

Thoracic Inlet: It enters the thorax by passing between the subclavian artery and vein.

Thoracic Cavity:

Right Phrenic Nerve:
Descends along the right side of the pericardium, within the fibrous pericardium.
Passes anterior to the root of the right lung.
Innervates the diaphragm.

Left Phrenic Nerve:
Descends along the left side of the pericardium.
Passes anterior to the root of the left lung.
Innervates the diaphragm.

Question 4

function of phrenic nerve

Answer 4

Motor Innervation: Supplies the diaphragm, the primary muscle of respiration.

Sensory Innervation: Provides sensory fibers to the central tendon of the diaphragm, pericardium, mediastinal & diaphragmatic pleura.