Anatomy of the Vessels and Nerves of the Head and Neck (Angioneurology) - Chornokulskyi S.T. 2009

Nerves of the Head and Neck
Vagus nerve

[X] (n. vagus) (Fig. 44)

Mixed nerve, containing three nuclei:

Nucleus of the solitary tract (nuc. tracti solitarii) (shared with Cranial Nerves VII and IX), nucleus ambiguus (nuc. ambiguus) (shared with cranial nerves IX and XI), and the dorsal nucleus of the vagus nerve (nuc. dorsalis n. vagi) — which is parasympathetic.

The rootlets (10–12) of the nerve emerge posterior to the olive and inferior to the rootlets of cranial nerve IX. The fiber COMPOSITION OF THE rootlets and the nerves themselves for both the X and IX pairs is fundamentally similar. Cranial nerve X also exits through the jugular foramen. Within the jugular foramen lies the superior ganglion (ganglion superius) of the nerve, and inferior to it is the inferior ganglion (ganglion inferius). The vagus nerve also contains intraneural microganglia—clusters of autonomic Neurons that serve as centers for the automatic regulation of internal organ Functions.

The n. vagus is the longest of the cranial nerves, and its area of innervation extends from the HEAD to the viscera of the Abdominal cavity. The vagus nerve is a component of the neurovascular bundle of the neck.

In the thoracic cavity, the left vagus nerve passes along the anterior surface of the aortic arch, while the right passes anterior to the right Subclavian Artery. At these locations, both the left and right vagus nerves give off their respective recurrent nerves, which loop inferior and posterior to these vessels as they ascend back to the neck.

In the thoracic cavity, the vagus nerves pass posterior to the roots of the Lungs; the left vagus nerve shifts to the anterior surface of the Esophagus, and the right to the posterior surface, forming the anterior and posterior vagal trunks.

In the abdominal cavity, the anterior vagal trunk extends toward the Liver, branching into hepatic branches (rr. hepatici), while the posterior trunk extends to the celiac plexus, sending out celiac branches (rr. coeliaci).

Four topographical segments of the vagus nerve are distinguished:

I. Cranial segment

II. Cervical segment

III. Thoracic segment

IV. Abdominal segment

I. The cranial segment terminates at the level of the upper border of the inferior ganglion and gives off the following branches:

1. Meningeal branch (r. meningeus), which branches off at the level of the superior ganglion, returns to the cranial cavity, and innervates the dura mater of the posterior cranial fossa;

2. Auricular branch (r. auricularis), which enters the mastoid canaliculus of the Temporal bone and, upon exiting, innervates the Skin of the posterior part of the auricle, the posterior wall of the external acoustic meatus, and the tympanic membrane. The Water/144.html">Origin of the auricular branch features the r. communicans cum nervo glossopharyngeo, as well as a connection with the superior cervical ganglion of the Sympathetic trunk.

II. The cervical segment

— this is the section of the nerve between the inferior ganglion and the branching point of the recurrent nerve (inclusive). This nerve segment gives rise to the following branches:

3. Pharyngeal branches (rr. pharyngei) run toward the pharyngeal wall, within the substance of which they form the pharyngeal plexus (plexus pharyngeus) together with cranial nerve IX and Branches of the sympathetic trunk. Its branches innervate the superior and middle pharyngeal Constrictor Muscles, the Muscles of the soft palate (except for the m. tensor veli palatini), and the pharyngeal mucosa.

4. Superior laryngeal nerve (n. laryngeus superior) has two branches — external and internal (rr. externus et internus). The external branch innervates the inferior pharyngeal constrictor Muscle and the cricothyroid muscle, while the internal branch innervates the laryngeal mucosa superior to the level of the rima glottidis, the mucosa of the epiglottis, and the ROOT of the Tongue (general and gustatory sensation). The superior laryngeal nerve has a communicating branch with the recurrent laryngeal nerve (r. communicans cum nervo laryngeo recurrente).

5. Superior cervical cardiac branches (rr. cardiaci cervicales superiores). The right branches run to the deep cardiac plexus, and the left to the superficial plexus. It is believed that they also convey the depressor nerve, which regulates Blood pressure reflexively.

6. Recurrent laryngeal nerve (n. laryngeus recurrens). As noted above, after branching off, the left recurrent nerve loops around the aortic arch, and the right around the subclavian artery. Each of them ascends back to the neck and, via its terminal branch—the inferior laryngeal nerve (n. laryngeus inferior)—reaches the Larynx, where it innervates all laryngeal muscles (except the cricothyroid), the laryngeal mucosa inferior to the level of the rima glottidis, the thyroid and Parathyroid glands, and the cervical Lymph Nodes. Along the course of the recurrent laryngeal nerve, additional branches are given off: tracheal branches (rr. tracheales), esophageal branches (rr. oesophageales), pharyngeal branches (rr. pharyngeales), and inferior cervical cardiac branches (rr. cardiaci cervicales superiores), which run to the deep cardiac plexus.

III. The thoracic segment of the vagus nerve contains only sensory and parasympathetic fibers, whereas the somatomotor fibers have been "utilized" to innervate the upper third of the esophagus and the muscles of the larynx. Further down, the digestive and respiratory systems contain only non-striated (smooth) musculature, which is innervated by parasympathetic fibers. Descending along the walls of the esophagus, the vagus nerves form the esophageal plexus (plexus oesophageus) and somewhat lose their appearance as distinct trunks. Both nerves, together with the esophagus, pass through the esophageal hiatus into the abdominal cavity.

Branches of the thoracic segment of the n. vagus

7. Thoracic cardiac branches (rr. cardiaci thoracici) run to the deep cardiac plexus and the roots of the lungs.

8. The bronchial branches (rr. bronchiales), along with branches from the sympathetic trunk, form the pulmonary plexus (plexus pulmonalis) within the walls of the bronchial tree. It innervates the smooth muscle and Glands of the Bronchi, and provides general sensation to the bronchi, lungs, and visceral Pleura.

9. The tracheal branches (rr. tracheales), together with corresponding branches of the recurrent laryngeal nerve, form a plexus (plexus trachealis) in the tracheal wall.

10. The esophageal plexus (plexus oesophagealis) is formed by branches from the anterior and posterior vagal trunks, esophageal branches of the recurrent laryngeal nerve, and branches of the sympathetic trunk.

IV. Abdominal part and its branches:

11. The anterior vagal trunk (truncus vagalis anterior) runs along the lesser curvature of The Stomach and contains fibers from both the right and left vagus nerves. This trunk gives rise to the following:

12. Anterior gastric branches (rr. gastrici anteriores), which combine with sympathetic fibers to form the anterior gastric plexus:

13. Hepatic branches (rr. hepatici), which are terminal branches of the anterior vagal trunk, passing between the peritoneal folds of the lesser omentum to the porta hepatis.

14. The posterior vagal trunk (truncus vagalis posterior) gives off the following branches:

15. Posterior gastric branches (rr. gastrici posteriores) supplying the posterior wall of the stomach:

16. Celiac branches (rr. coeliaci) accompany the left gastric artery and represent the parasympathetic component of the celiac plexus (plexus coeliacus).

17. Renal branches (rr. renales) are offshoots of the celiac branches that travel toward the Kidney and, together with sympathetic nerves, form the renal plexus (plexus renalis) within it.

From the celiac plexus, vagal nerve fibers reach nearly all abdominal Organs down to the descending or sigmoid colon.

The vagus nerve has numerous communicating branches with the VII, IX, XI, and XII cranial nerve pairs and the sympathetic trunk.

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Fig. 44. Vagus nerve (schematic):

1 - communicating branch between the X and VII cranial nerve pairs;

2 - communicating branch between the X and IX cranial nerve pairs;

3 - Accessory nerve (n. accessorius);

4 - communicating branch between the X and XII cranial nerve pairs;

5 - communicating branch between the X cranial nerve pair and the superior cervical sympathetic ganglion;

6 - tongue (lingua);

7 - Hyoid bone (os hyoideum);

8 - larynx (larynx);

9 - Trachea (trachea);

10 - right recurrent laryngeal nerve (n. laryngeus recurrens dexter);

11 - left recurrent laryngeal nerve (n. laryngeus recurrens sinister);

12 - left vagus nerve (n. vagus sinister);

13 - aorta (aorta);

14 - lung (pulmo);

15 - Heart (cor);

16 - Diaphragm (diaphragma);

17 - stomach (ventriculus);

18 - liver (hepar);

19 - celiac plexus (plexus coeliacus);

20 - right lung (pulmo dexter);

21 - esophagus (oesophagus);

22 - branches of the inferior laryngeal nerve (rr. n. laryngei inferioris);

23 - superior laryngeal nerve (n. laryngeus superior);

24 - branch of the accessory nerve to the trapezius muscle;

25 - sternocleidomastoid muscle (m. sternocleidomastoideus);

26 - accessory nerve within the jugular foramen (foramen jugulare);

27 - nucleus of the accessory nerve (nuc. n. accessorii);

28 - ambiguus nucleus (nuc. ambiguus);

29 - dorsal nucleus of the vagus nerve (nuc. dorsalis n. vagi);

30 - nucleus of the solitary tract (nuc. tractus solitarii);

31 - Facial Nerve (n. facialis)

ORGAN OF TASTE (organum gustatorium)

Receptors are located in the taste buds (gemma gustatoria) of the lingual taste papillae, soft palate, and palatine arches. Taste sensory epithelial Cells (epitheliocytus sensorius gustatorius) feature specialized chemoreceptors in the form of microvilli (microvilli) located at the apices of the taste buds.

The nerve fibers conducting impulses from the taste receptors belong to the VII, IX, and X pairs of cranial nerves.

The Cell bodies of the first-order neurons of the gustatory pathway are located in the geniculate ganglion of the intermediate nerve, as well as in the superior and inferior ganglia of the IX and X cranial nerve pairs. Dendrites of the pseudounipolar neurons from these ganglia, running within the branches of the VII, IX, and X cranial nerves, conduct taste sensations, whereas the axons of these same neurons reach the cell bodies of the second-order neurons (nucleus of the solitary tract). The second-order neurons maintain extensive connections with the autonomic and somatomotor nuclei of the V, IX, and X cranial nerve pairs, which regulate swallowing, chewing, and autonomic Reflexes (nausea, vomiting). Axons of the second-order neurons partially decussate and reach the cell bodies of the third-order neurons (ventrobasal nucleus of the thalamus)*. Axons of the third-order neurons pass through the posterior limb of the internal capsule to the gustatory cortex located in the lower region of the postcentral gyrus and the uncus.

Fig. 45. Pathway of the gustatory analyzer:

1 - geniculate ganglion (ganglion geniculatum) - 1st neuron;

2 - chorda tympani (chorda tympani) - gustatory fibers;

3 - nucleus of the solitary tract (nuc. tractus solitarii) - 2nd neuron;

4 - lingual nerve (n. lingualis);

5 - Glossopharyngeal nerve (n. glossopharyngeus) and vagus nerve (n. vagus) - gustatory fibers