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

Nerves of the Head and Neck
Facial Nerve

Facial nerve [VII], nervus facialis, (Fig. 27, 28, 38, 39)

It is studied together with the intermediate nerve (n. intermedius) under the same number.

The nerve nuclei are located in the dorsal part of the Pons:

✵ the facial nerve Nucleus (nuc. n. facialis) is somatomotor, consisting of upper and lower parts that determine the features of rr. corticonuclearis;

✵ the superior salivatory nucleus (nuc. salivatorius superior), and

✵ the lacrimal nucleus (nuc. lacrimalis) are parasympathetic;

✵ the Nucleus of the solitary tract (solitary nucleus) nuc. tractus solitarii is sensory and shared with the IX and X pairs of Cranial Nerves.

The latter three nuclei belong to the intermediate nerve.

The nerve ROOT emerges at the cerebellopontine angle, with the root of n. intermedius being separate and situated between the facial nerve proper and the Vestibulocochlear nerve, hence the name—intermediate.

The roots of the VII pair of cranial nerves comprise:

✵ axons of somatomotor Neurons;

✵ axons of pseudounipolar neurons of the geniculate ganglion (ganglion geniculi), running to The Nucleus of the solitary tract;

✵ axons of parasympathetic nuclei as preganglionic fibers;

The intermediate nerve consists of preganglionic parasympathetic fibers and dendrites of pseudounipolar neurons of the ganglion geniculi, whereas the facial nerve proper consists of axons of somatomotor neurons. Overall, the VII pair of cranial nerves passes through the internal acoustic meatus and canal, and then extends into the facial canal, following its course.

At the genu of the canal lies the geniculate ganglion (ganglion geniculi), after which the intermediate nerve gives off:

1) the greater petrosal nerve (n. petrosus major), and closer to the stylomastoid foramen—

2) the chorda tympani.

Within the descending part of the canal, the first branch of the facial nerve proper—the stapedial nerve—also branches off.

3) the stapedial nerve (n. stapedius), which innervates the Muscle of the same name. Thus, only the facial nerve proper exits the canal through the stylomastoid foramen to innervate the Muscles derived from the 2nd pharyngeal arch.

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Fig. 38. Facial and intermediate nerves (schematic):

1 - Midbrain (mesencephalon);

2 - pons (pons);

3 - Medulla Oblongata (medulla oblongata);

4 - Cerebellum (cerebellum);

5 - root of intermediate nerve (radix n. intermedii);

6 - root of facial nerve (radix n. facialis);

7 - internal acoustic opening (porus acusticus internus);

8 - internal acoustic meatus (meatus acusticus internus);

9 - facial canal (canalis n. facialis);

10 - genu of facial canal (geniculum canalis n. facialis);

11 - hiatus for greater petrosal nerve (hiatus canalis n. petrosi majoris);

12 - stapedius nerve (n. stapedius);

13 - chorda tympani;

14 - stylomastoid foramen (foramen stylomastoideum);

15 - lacrimal gland (glandula lacrimalis);

16 - lacrimal nerve (n. lacrimalis);

17 - maxillary nerve (n. maxillaris);

18 - pterygopalatine ganglion (ganglion pterygopalatinum);

19 - pterygoid canal (canalis pterygoideus);

20 - nasal glands (glandulae nasales);

21 - fungiform papillae of Tongue (papillae fungiformes);

22 - sublingual gland (glandula sublingualis);

23 - submandibular gland (glandula submandibularis);

24 - submandibular ganglion (ganglion submandibulare);

25 - nucleus of facial nerve (nuc. n. facialis);

26 - superior salivatory nucleus (nuc. salivatorius superior) and lacrimal nucleus (n. lacrimalis);

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

28 - parotid plexus (plexus parotideus);

29 - preganglionic parasympathetic fibers within the greater petrosal nerve;

30 - postganglionic parasympathetic fibers as part of the lacrimal nerve;

31 - lingual nerve (n. lingualis);

32 - pseudounipolar neurons of the geniculate ganglion of the facial nerve;

33 - postganglionic parasympathetic fibers to the Salivary Glands

Fig. 39. Branches of the facial nerve (schematic):

1 - temporal branches (rr. temporales);

2 - zygomatic branches (rr. zygomatici);

3 - buccal branches (rr. buccales);

4 - marginal mandibular branch (r. marginalis mandibularis);

5 - cervical branch (r. cervicalis) s. r. colli;

6 - digastric branch (r. digastricus);

7 - posterior auricular nerve (n. auricularis posterior);

8 - chorda tympani;

9 - geniculate ganglion (ganglion geniculi) and greater petrosal nerve (n. petrosus major)

1. The greater petrosal nerve (n. petrosus major) contains exclusively preganglionic parasympathetic fibers—the axons of neurons from the superior salivatory and lacrimal nuclei—which are secretory in function.

The nerve exits the canal through the hiatus of the canal for the greater petrosal nerve (hiatus canalis nervi petrosi majoris), runs along the groove of the same name on the anterior surface of the petrous part of the Temporal bone, and leaves the cranial cavity by piercing the Cartilage of the foramen lacerum. Afterward, the greater petrosal nerve travels together with the deep petrosal nerve within the pterygoid canal (as the nerve of this canal, n. canalis pterygoidei) and reaches the pterygopalatine ganglion (see p. 76).

2. The chorda tympani consists of taste fibers (dendrites of pseudounipolar neurons from the geniculate ganglion) and preganglionic parasympathetic fibers. The nerve branches off into the canaliculus of the same name in the temporal bone and, within the tympanic cavity, lies between the malleus and incus on the tympanic membrane. After emerging from the tympanic cavity through the petrotympanic fissure, the chorda tympani joins the lingual nerve. The taste fibers of the chorda tympani reach the taste buds of the mucous membrane on the anterior 2/3 of the tongue, whereas the preganglionic parasympathetic fibers reach the submandibular and sublingual ganglia (see p. 81).

Somatic motor branches of the facial nerve:

3. Stapedius nerve (n. stapedius).

4. Posterior auricular nerve (n. auricularis posterior) to the occipital belly of the occipitofrontalis muscle and to the posterior and superior auricular muscles.

5. Digastric branch (r. digastricus) to the posterior belly of the digastric muscle.

6. Stylohyoid branch (r. stylohyoideus) to the stylohyoid muscle.

After giving off these branches, the facial nerve courses anteriorly and forms the intraparotid plexus (plexus intraparotideus) within the substance of the parotid gland. The branches of this plexus diverge radially, forming the "greater goose's FOOT" (pes anserinus major). This topographical arrangement of the facial nerve branches must be carefully considered during surgical interventions. All of these branches exclusively innervate the Muscles of facial expression (Figs. 39, 39a).

7. Temporal branches (rr. temporales) to the frontal belly of the occipitofrontalis muscle, the anterior and superior auricular muscles, and the Muscles surrounding the palpebral fissure.

8. Zygomatic branches (rr. zygomatici) supplying the zygomaticus major and orbicularis oculi muscles.

9. Buccal branches (rr. buccales) supplying the buccinator and facial muscles superior to the oral fissure.

10. Marginal mandibular branch (ramus marginalis mandibularis) supplying the facial muscles inferior to the oral fissure.

11. Cervical branch (r. colli) innervating the platysma, joining the transverse cervical nerve (from the Cervical plexus) to form the superficial cervical loop (ansa cervicalis superficialis).

Thus, the cranial nerve VII innervates:

✵ muscles derived from the second pharyngeal arch;

✵ secretomotor fibers to all HEAD glands (except the parotid gland) via the pterygopalatine, submandibular, and sublingual parasympathetic ganglia;

✵ taste sensation from the mucosa of the anterior 2/3 of the tongue.

The facial nerve has numerous connections with the cranial nerves V and IX and the cervical Spinal Nerves.

Fig. 39a. Topography of the facial nerve branches