Vagus nerve

Intro

1.     Vagus nerve is the longest cranial nerve, from brainstem till splenic flexure of colon

2.     Aka Pneumogastric nerve or the wanderer

3.     Mixed motor and sensory nerve

4.     Bilateral lesion to the X cranial nerve is fatal since it causes

a.     Loss of parasympathetic supply to heart à Tachyarrhythmias

b.      Laryngeal muscle paralysis -à Asphyxia

Component	Nucleus	Ganglion	Peripheral Nerve and target organs	Function
Branchial efferent	Ambigus		Pharyngeal nerve à Uvula, tensor veli palatini, Stylopharyngeus, Styloglossus Sup Laryngeal nerveà Cricothyroid muscle  (stretch vocal folds) Recurrent Laryngeal nerveà PosteriorCricoarythenoids (abduct VC) Lateral Cricoarythenoids (adduct VC) Arythenoids Thyroarythenoids	Swallowing Speech
Para sympathetic Efferent	Dorsal motor nucleus of X		Esophagus, cardiac, pulmonary, gastric, celiac plexus SA node of Atrium Carotid sinus(Baro)/ Body (Chemo) The sm and glands of GIT	Peristalsis Heart rate and rhythm BP regulation
Visceral sensation	Solitary nucleus	Inferior ganglion (Nodusum)	..	..
Special sensation	Solitary nucleus	Inferior ganglion	Epiglottis and Taste buds	Taste
General sensation	Trigemina	Superior Ganglion (jugular)	Posterior meninges, External ear, auditory meatus,	Cutaneous sensation

 

Course of Vagus nerve

1.It exit the medulla oblongata at the post olivary sulcus between olive and inferior cerebellar peduncle inferior to the flocculus’ (Cisternal portion)

2. Together with cranial portion of accessory nerve, it forms the vagua accessory nerve complex to enter jugular foramen

This complex is divided from the more superiorly located glossopharyngeal nerve by the fibrous band or a bony crest.

3. The vagus nerve enter its superior ganglion in the jugular fossa of the petrous temporal bone.

The auricular nerve arises from the superior ganglion. It travels in the mastoid cannaliculus lateral to the jugular foramen. Later on it exit the skull base via tympanomastoid suture to supply the posterior aspect of pinna and external auditory meatus.

1cm distal to the superior ganglion, the vagus nerve meets the inferior ganglion of nodusom, which has a larger size since it contains the cell bodies of the visceral and special sensory afferent nerve supplying the viscera.

1.   Upon exiting the jugular foramen, the glossopharyngeal nerve and vagus accessory complex is separated by dura sheath, but the branchial motor nerves soon rejoin their effector at the pharynx. The pharyngeal nerve is therefore formed and penetrate the middle constrictor muscles before supplying the uvula, and the pharyngeal musculatures. Tensor veli palatini, palatoglossus, palatopharyngeus by Vagus nerve; Stylopharyngeus by Gloospharyngeal nerve

6. In the neck the vagus nerve run together with IJV posterolaterally and ICA anteromedially within the carotid sheath

It joints with the glossopharyngeal nerve to form nerve of Hering to supply the carotid sinus and body

It gives off superior laryngeal nerve to supply Cricothyroid muscle, which is responsible to stretch the vocal fold.

It also gives out branches to reach the superior and inferior cardiac plexus which is mainly the right vagus nerve function. Vagus nerve stimulation is only performed on its left counterpart to avoid cardiac complication (This is my understanding at this moment, but I found books stating that the SA node is by the R vagus nerve; VA node by L vagus nerve.. Puzzled.. somebody help to clear my doubt, please??)

7.The right vagus nerve and its left counterpart take a slightly different course while descending from the neck to the abdominal cavity.

8. The right vagus nerve runs lateral to the CCA and cross anterior to the proximal part of subclavian artery to reach the thoracic cavity. At this juncture, it gives rise to right recurrent laryngeal nere which loop around the subclavian artery before ascending to supply the laryngeal muscles with the exception of cricothyroid muscle. (Posterior cricoarythenoid to abduct VC whilst Lateral cricoarythenoid to adduct VC)

9. The left vagus nerve runs in between the left CCA and L Brachiocephalic artery and cross in front of aortic arch. The Left recurrent laryngeal loops below the aortic artery and ascend lateral to the trachea to supply the larynx

10. 

10. The vagus nerve pierces the esophageal hiatus and gives rise to the gastric nerves, celiac plexus and etc.

The right Vagus nerve is distributed in the anterosuperior surface of abdominal viscera e.g. fundus, liver, omentum

Left vagus nerve assume a posteroinferior distribution.