vagus nerve medical students

1. VAGUS NERVE

2. COARSE
Nerve takes it origin from the anterolateral surface
of upper part of medulla oblongata between the
olive and the inferior cerebral peduncle.
Then it travels laterally leaving the skull through
jugular foramen.
Descends vertically in the neck within the carotid
sheath.

3. RIGHT VAGUS NERVE gives rise to the right
recurrent laryngeal nerve, which hooks around
the right subclavian artery and ascends into the
neck between the trachea and esophagus. The
right vagus then crosses anterior to the right
subclavian artery, runs posterior to the superior
vena cava, descends posterior to the right main
bronchus, and contributes to cardiac, pulmonary,
and esophageal plexuses. It forms the posterior
vagal trunk at the lower part of the esophagus
and enters the diaphragm through the
esophageal hiatus.

4. LEFT VAGUS NERVE enters the thorax between left
common carotid artery and left subclavian artery
and descends on the aortic arch. It gives rise to the
left recurrent laryngeal nerve, which hooks around
the aortic arch to the left of the ligamentum
arteriosum and ascends between the trachea and
esophagus. The left vagus further gives off thoracic
cardiac branches, breaks up into pulmonary plexus,
continues into the esophageal plexus, and enters
the abdomen as the anterior vagal trunk in the
esophageal hiatus of the diaphragm.

6. Branches:
In the jugular foremen, superior ganglion gives:
- Auricular nerve
- Meningeal nerves
Branches arising in neck are:
- Pharyngeal nerve
- Carotid branches
- Superior laryngeal nerve
- Cardiac branches
- Recurrent laryngeal nerve

7. - Meningeal branches → dura of posterior cranial fossa
- Auricular branches → concha and root of auricle, post
half of ext auditory meatus, outer surface of tympanic
membrane
- Pharyngeal branch → pharyngeal plexus, muscles of
pharynx and soft palate (except tensor veli palatini
- carotid branches → carotid body and carotid sinus
-Superior laryngeal nerve
1)external laryngeal nerve→ cricothyroid, inferior
constrictor and pharyngeal plexus
2) internal laryngeal nerve→ mucous membrane of
larynx upto vocal cords

8. - Recurrent laryngeal nerve
supplies:
1) All intrinsic muscles of larynx except
cricothyroid
2) Sensory below the level of vocal cords
3) Cardiac branches to deep cardiac
plexus
4) Branches to trachea and oesophagus
5) To inferior constrictor
- Cardiac branches → cardiac plexus

9. Nuclei
The vagus nerve includes axons which emerge from or converge onto
four nuclei of the medulla:
1) The dorsal nucleus of vagus nerve — which sends parasympathetic
output to the viscera, especially the intestines
2) The nucleus ambiguus — which gives rise to the branchial efferent
motor fibers of the vagus nerve and preganglionic parasympathetic
neurons that innervate the heart
3) The solitary nucleus — which receives afferent taste information
and primary afferents from visceral organs
4) The spinal trigeminal nucleus — which receives information about
deep/crude touch, pain, and temperature of the outer ear, the dura of
the posterior cranial fossa and the mucosa of the larynx

10. FUNCTION:
- General visceral efferent (GVE) — provides
parasympathetic innervation to glands of mucous
membranes of the pharynx, larynx, organs in the neck,
thorax, and abdomen.
- Special visceral efferent (SVE) — innervates skeletal
muscles of the pharynx and larynx.
- General somatic afferent (GSA) — carries sensation from
the external auditory meatus and tympanic membrane.
- General visceral afferent (GVA) — carries information
from the thoracic and abdominal viscera; aortic body and
arch.
- Special visceral afferent (SVA) — carries taste of the
epiglottis region of the tongue.

11. CLINICALS:
The vagus nerve is tested clinically by comparing the palatal
arches on the two sides.
On the paralyzed side therr will be no arching and uvula is
pulled to normal side.
PARALYSES OF X NERVE PRODUCES:
1) Nasal regurgitation of swallowed liquid
2) Nasal twang in voice
3) Hoarseness
4) Flattening of palatal arch
5) Cadaveric position of vocal cord
6) Dysphagia