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

Nerves of the Head and Neck
Trigeminal nerve

V (n. trigeminus) (Fig. 27, 28, 33, 34, 35)

It has 4 nuclei, three of which are sensory:

✵ Spinal Nucleus (nuc. spinalis n. trigemini) — for pain and Temperature Sensation;

✵ Pontine (chief) nucleus (nuc. pontinus (nuc. principalis n. trigemini) — for Touch sensation;

✵ Mesencephalic nucleus (nuc. mesencephalicus n. trigemini) — for proprioceptive sensation;

and one somatomotor nucleus — the motor nucleus (nuc. motorius n. trigemini).

As the names of the sensory nuclei suggest, they are located along the entire Brainstem, while the motor nucleus lies in the Pons.

At the border between the pons and the middle cerebellar peduncles lie two roots of the trigeminal nerve.

The larger is the sensory ROOT (radix sensoria), formed by the axons of pseudounipolar Neurons of the trigeminal ganglion (ganglion trigeminale), which enter the Brain, divide into ascending and descending branches, and form synaptic connections with the sensory neurons of the three nuclei.

The smaller is the motor root (radix motoria), which is a bundle of axons originating from the somatomotor neurons of the motor nucleus and emerging from the brain.

The trigeminal ganglion (Gasserian ganglion, ganglion trigeminale Gasseri) is about 1.5 cm long and is located in the trigeminal cavity (cavum trigeminale) of the dura mater, which together with the ganglion forms the trigeminal impression on the petrous part of the Temporal bone.

The peripheral processes of the pseudounipolar ganglionic neurons emerge from its convex border and form three major branches, known as the nerves:

I — Ophthalmic nerve (n. ophthalmicus);

II — Maxillary nerve (n. maxillaris);

III — Mandibular nerve (n. mandibularis).

Unlike the two preceding nerves, the mandibular nerve is mixed because it incorporates the entire motor root, i.e., the axons of the somatomotoneurons from the nuc. motorius.

I. Ophthalmic nerve (n. ophthalmicus), Fig. 33

This sensory nerve, much like Cranial Nerves III, IV, and VI, pierces the lateral wall of the cavernous sinus, gives off the tentorial branch (r. tentorius), and enters the Orbit through the superior orbital fissure. Within the orbit, the nerve branches into three nerves:

1. Frontal nerve (n. frontalis);

2. Lacrimal nerve (n. lacrimalis);

3. Nasociliary nerve (n. nasociliaris).

1. The frontal nerve (n. frontalis) is the largest branch of the ophthalmic nerve; it runs along the superior wall of the orbit and divides into the supraorbital and supratrochlear nerves.

✵ The supraorbital nerve (n. supraorbitalis) passes through the supraorbital notch (foramen) to the Skin of the forehead and scalp, reaching the temporal and parietal regions. In addition, it supplies the skin and conjunctiva of the upper eyelid, the medial angle of the eye, and the frontal sinus.

✵ The supratrochlear nerve (n. supratrochlearis) passes above the trochlea of the superior oblique Muscle and supplies the upper eyelid, the skin of the root of the Nose, and the lacrimal sac.

2. The lacrimal nerve (n. lacrimalis) runs along the lateral wall of the orbit toward the lacrimal gland, as well as the skin and conjunctiva of the eyelids near the lateral angle of the eye, innervating them. The lacrimal nerve communicates via a branch with the zygomatic nerve, from which it receives postganglionic parasympathetic fibers (originating from the pterygopalatine ganglion) that provide secretory innervation to the lacrimal gland.

3. The nasociliary nerve (n. nasociliaris) lies on the medial wall of the orbit and gives off the following branches:

✵ Communicating branch with the ciliary ganglion (ramus communicans cum ganglio ciliari), acting as the sensory root (radix sensoria) of the ganglion.

✵ Long ciliary nerves (nn. ciliares longi) — 2–3 branches that innervate the fibrous and vascular Tunics of the Eyeball. Alongside these nerves, about 15 short ciliary nerves run from the ciliary ganglion to the eyeball (see CN III).

✵ Anterior ethmoidal nerve (n. ethmoidalis anterior) passes through the foramen of the same name into the cranial cavity, and then via the cribriform plate (lamina cribrosa) to the mucous membrane of the anterior Nasal cavity (nasal septum, lateral wall), frontal sinus, and also supplies the skin of the dorsum and apex of the nose, as well as the anterior meningeal branch (r. meningeus anterior).

✵ Posterior ethmoidal nerve (n. ethmoidalis posterior) passes through the foramen of the same name to supply the mucous membrane of the posterior ethmoidal Cells and the sphenoid sinus.

✵ Infratrochlear nerve (n. infratrochlearis) is the terminal branch of the n. nasociliaris, passing beneath the trochlea of the superior oblique muscle and anastomosing with the supratrochlear nerve. The n. infratrochlearis innervates the skin and conjunctiva of the eyelids near the medial angle of the eye, the lacrimal sac, and the lacrimal caruncle. Overall, through its connections with cranial nerves III, IV, VI, and VII, the ophthalmic nerve also provides proprioceptive sensitivity to the extraocular Muscles and some facial muscles.

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Fig. 33a. Distribution of the ophthalmic nerve (A) and the ciliary ganglion (B) (schematic): A:

1 - trigeminal ganglion (ganglion trigeminale);

2 - ophthalmic nerve (n. ophthalmicus);

3 - maxillary nerve (n. maxillaris);

4 - mandibular nerve (n. mandibularis);

5 - superior orbital fissure (fissura orbitalis superior);

6 - foramen rotundum;

7 - foramen ovale;

8 - lacrimal gland (glandula lacrimalis);

9 - sphincter pupillae muscle (m. sphincter pupillae);

10 - ciliary ganglion (ganglion ciliare);

11 - Internal Carotid Artery (a. carotis interna);

12 - Oculomotor nerve (n. oculomotorius);

13 - recurrent meningeal (tentorial) branch (r. meningeus recurrens (tentorius));

14 - frontal nerve (n. frontalis);

15,16 - medial and lateral Branches of the supraorbital nerve (rr. medialis et lateralis n. supraorbitalis);

17 - supratrochlear nerve (n. supratrochlearis);

18 - nasociliary nerve (n. nasociliaris);

19 - posterior ethmoidal nerve (n. ethmoidalis posterior);

20 - anterior ethmoidal nerve (n. ethmoidalis anterior);

21 - communicating branch with the ciliary ganglion (r. communicans cum ganglio ciliari);

22 - long ciliary nerves (nn. ciliares longi);

23 - lacrimal nerve (n. lacrimalis);

24 - communicating branch with the zygomatic nerve (r. communicans cum nеrvo zygomatico);

25 - postganglionic parasympathetic fibers;

26 - preganglionic parasympathetic fibers;

27 - postganglionic sympathetic fibers

Fig. 33a. B — ciliary ganglion (schematic diagram):

1 - ciliary ganglion (ganglion ciliare);

2 - sensory root from the nasociliary nerve (radix sensoria);

3 - nasociliary nerve (n. nasociliahs);

4 - oculomotor (parasympathetic) root from the autonomic nuclei of the cranial nerve III (radix parasympathica),

5 - sympathetic root (radix sympathica

6 - periaortic (sympathetic) carotid plexus (plexus carolicus);

7 - short ciliary nerves (nn. ciliares breves)

8 - inferior branch of the oculomotor nerve (r. inferior n. oculoniotorii);

9 - preganglionic parasympathetic fibers;

10 - somatomotor fibers of cranial nerve III;

11 - postganglionic parasympathetic fibers;

12 - postganglionic sympathetic fibers

II. Maxillary nerve (n. maxillaris), Fig. 34

Before exiting the Skull through the foramen rotundum, the nerve gives off the following branches:

1) meningeal branch (r. meningeus) and subsequently enters the pterygopalatine fossa. Within it, the nerve branches into:

2) ganglionic branches (rr. ganglionares) to the pterygopalatine ganglion, forming the sensory root of the pterygopalatine ganglion (radix sensoria g. pterygopalatini).

Pterygopalatine ganglion

The pterygopalatine ganglion (ganglion pterygopalatinum) (Fig. 14 a, 34 a, b) is a parasympathetic ganglion located in the fossa of the same name. Its parasympathetic root is the greater petrosal nerve (n. petrosus major), which consists of preganglionic parasympathetic fibers from the superior salivatory nucleus and lacrimal nucleus (from the VII cranial nerve and nervus intermedius) that synapse in the ganglion.

The sympathetic root of the ganglion is the deep petrosal nerve (n. petrosus profundus) (a branch of the internal carotid plexus), representing postganglionic sympathetic fibers from the superior cervical ganglion of the Sympathetic trunk.

Both petrosal nerves enter the ganglion through the pterygoid canal and are therefore referred to as the nerve of the pterygoid canal (n. canalis pterygoidei Vidii, or Vidian nerve) (Fig. 14 a).

Sensory root — ganglionic branches of the maxillary nerve (rr. ganglionares n. maxillaris).

Branches of the ganglion:

✵ Orbital branches (rr. orbitales), which initially run within the zygomatic nerve and branch off in the orbit to the lacrimal nerve as secretory fibers (see n. lacrimalis).

✵ Lateral and medial superior posterior nasal branches (rr. nasales posteriores superiores laterales et mediales) to the mucous membrane of the lateral and medial walls of the posterosuperior Regions of the nasal cavity.

Fig. 34. Branches of the maxillary nerve (schematic):

1 - trigeminal ganglion (ganglion trigeminale);

2 - ophthalmic nerve (n. ophthalmicus);

3 - maxillary nerve (n. maxillaris);

4 - mandibular nerve (n. mandibularis);

5 - pterygoid process (processus pterygoideus);

6 - pterygoid canal (canalis pterygoideus);

7 - pterygopalatine ganglion (ganglion pterygopalatinum);

8 - lacrimal nerve (n. lacrimalis);

9 - lacrimal gland (glandula lacrimalis);

10 - infraorbital nerve (n. infraorbitalis);

11 - posterior superior alveolar branches (rr. alveolares superiores posteriores);

12 - middle superior alveolar branch (r. alveolaris superior medius);

13 - anterior superior alveolar branches (rr. alveolares superiores anteriores);

14 - superior dental plexus (plexus dentalis superior);

15 - maxillary Teeth (dentes maxillae);

16 - gingiva (gingiva);

17 - inferior orbital fissure (fissura orbitalis inferior);

18 - zygomatic nerve (n. zygomaticus);

19 - greater palatine nerve (n. palatinus major);

20 - palatine arches, palatine tonsil, uvula;

27 - posterior nasal nerves (nn. nasales posteriores);

22 - sphenopalatine foramen (foramen sphenopalatinum);

23 - nasopalatine nerve (n. nasopalatinus);

24 - opening of the incisive canal (canalis incisivus);

25 - preganglionic parasympathetic fibers from the superior salivatory nucleus and lacrimal nucleus;

26 - postganglionic parasympathetic (secretory) fibers to the lacrimal gland via the communicating branch of the lacrimal and zygomatic nerves

✵ Inferior posterior nasal branches (rr. nasales posteriores inferiores). All posterior nasal branches run into the nasal cavity through the sphenopalatine foramen.

✵ The nasopalatine nerve (n. nasopalatinus), the longest branch of the posterior nasal nerves, runs along the nasal septum and passes through the incisive canal to reach the mucosa of the hard palate (general sensory and secretory innervation).

✵ The greater palatine nerve (n. palatinus major) passes through the canal of the same name to reach the mucosa of the soft palate and posterior regions of the hard palate

✵ The lesser palatine nerves (nn. palatini minores) descend through the lesser palatine canals to the mucosa of the soft palate and palatine Tonsils.

✵ The pharyngeal nerve (n. pharyngeus) innervates the pharyngeal mucosa.

Fig. 34 a. Pterygopalatine fossa in sagittal section. Pterygopalatine ganglion roots, branches, and topography from the right side, lateral view (semi-schematic):

1 - greater petrosal nerve (n. petrosus major) — parasympathetic root (radix parasympathica);

2 - deep petrosal nerve (n. petrosus profundus) - sympathetic root (radix sympathica);

3 - nerve of the pterygoid canal (n. canalis pterygoidei);

4 - maxillary nerve (n. maxillaris);

5 - greater palatine nerve (n. palatinus major);

6 - pterygopalatine ganglion (ganglion pterygopalatinum);

7,8 - posterior superior alveolar branches (rr. alveolares superiores posteriores);

9 - ganglionic branches of maxillary nerve (rr. gangtionares n. maxillaris) - radix senssor

10 - orbital branch (r. orbitalis);

11 - infraorbital nerve (n. infraorbitalis);

12 - posterior nasal nerves (nn. nasales posteriores)

Fig. 34 b. Pterygopalatine ganglion, its roots and branches (schematic diagram):

1 - superior salivatory and lacrimal nuclei (nuclei salivatorius superior et lacrimalis);

2 - geniculate ganglion (ganglion geniculi);

3 - Facial Nerve (n. facialis);

4 - greater petrosal nerve (n. petrosus major);

5 - trigeminal ganglion (ganglion trigeminale);

6 - nerve of pterygoid canal (n. canalis pterygoidei);

7 - internal carotid plexus (plexus caroticus internus);

8 - deep petrosal nerve (п. petrosus profundus);

9 - superior cervical ganglion of sympathetic trunk (ganglion cervivale superius trunci sympathici);

10 - intermediolateral nucleus (nuc. intermediolateralis);

11 - lacrimal nerve (n. lacrimalis);

12 - zygomatic nerve (n. zygomaticus);

13 - maxillary nerve (n. maxillaris);

14 - pterygopalatine ganglion (ganglion pterygopalatinum);

15 - posterior superior nasal branches (rr nasales posteriores superiores);

16 - posterior inferior nasal branches (rr. nasales posteriores inferiores);

17 - nasopalatine nerve (n.nasopalarinus);

18,19 - palatine branches (rr. palatini);

20 - greater palatine nerve (n. palatinus major);

21 - lesser palatine nerves (nn. palatini minores);

22 - pharyngeal nerve (n. pharyngeus)

3. The direct continuation of the maxillary nerve is the infraorbital nerve (n. infraorbitalis), which passes through the inferior orbital fissure into the infraorbital sulcus and canal, and exits the orbit via the infraorbital foramen. Here it forms a "minor goose's FOOT" (pes anserinus minor) with the following branches:

✵ Inferior palpebral branches (rr. palpebrales inferiores) to the skin of the lower eyelid:

✵ External and internal nasal branches (rr. nasales externi et interni) to the nasal wing and Vestibule of the nose:

✵ Superior labial branches (rr. labiales superiores) to the skin and mucous membrane of the upper lip.

Along the course of the infraorbital nerve, the following branches are given off:

4. Superior alveolar nerves (nn. alveolares superiores), which include posterior, middle, and anterior branches (rr. alveolares superiores posteriores, medii et anteriores), corresponding to the molars, premolars, canines, and incisors.

These branches reach the alveolar process by piercing the corresponding canals of the Maxilla, and within the canals, they give off small branches to the mucosa of the maxillary sinus (explaining toothache during sinusitis). In dental practice, so-called "tuberosity anesthesia" is used to block the rr. alveolares superiores posteriores where they enter the alveolar foramina and canals of the maxilla tuber (during Treatment of the upper molars).

The posterior, middle, and anterior branches form the superior dental plexus (plexus dentalis superior) above the roots of the teeth and gingiva, from which the superior dental and gingival branches (rr. dentales et gingivales superiores) arise.

5. Zygomatic nerve (n. zygomaticus) enters the orbit through the inferior orbital fissure, runs along its lateral wall, and reaches the zygomaticoorbital foramen. The nerve penetrates the substance of the Zygomatic bone, where it divides into the zygomaticotemporal and zygomaticofacial branches (rr. zygomaticotemporalis et zygomaticofacialis).

They innervate the skin of the temporal and zygomatic regions. As noted above, the n. zygomaticus transmits secretory fibers (rr. orbitales) from the pterygopalatine ganglion to the lacrimal nerve (n. lacrimalis), which innervate the lacrimal gland (gl. lacrimalis).

Through its connections with the facial nerve, the maxillary nerve also provides proprioceptive sensitivity to the facial muscles.

III. Mandibular nerve (n. mandibularis), Fig. 35

This is a mixed nerve that leaves the cranial cavity through the foramen ovale and enters the infratemporal fossa. Here it gives off the following branches:

1. Meningeal branch, or spinous nerve (r. meningeus, s. n. spinosus), which returns to the dura mater of the middle cranial fossa through the foramen spinosum:

2. To the muscles derived from the 1st pharyngeal arch:

✵ Masseteric nerve (n. massetericus) to the masseter muscle (m. masseter);

✵ Deep temporal nerves (nn. temporales profundi) to the temporalis muscle (m. temporalis);

✵ Lateral and medial pterygoid nerves (nn. pterygoidei lateralis et medialis) to the corresponding masticatory muscles.

✵ To the tensor veli palatini and tensor tympani muscles (nn. musculi tensores veli palatini et tympani), as branches of the medial pterygoid nerve (n. pterygoidei medialis).

3. Buccal nerve (n. buccalis), pierces the buccinator muscle and runs toward the mucous membrane of the cheek and the angle of the Mouth.

4. Auriculotemporal nerve (n. auriculotemporalis) arises by two roots from the mandibular nerve, loops around the middle meningeal artery, and runs toward the skin of the temporal region. It gives off the following branches:

✵ Articular branches (rr. articulares) to the temporomandibular joint;

✵ Nerve of the external acoustic meatus (n. meatus acustici externi);

✵ Branches of the tympanic membrane (rr. membranae tympani);

✵ Parotid branches (rr. parotidei), containing secretory fibers from the otic ganglion;

✵ Anterior auricular nerves (nn. auriculares anteriores) to the skin of the anterior PARTS OF THE auricle;

✵ Communicating branches with the facial nerve (rr. communicantes cum nervo faciale).

5. The lingual nerve (n. lingualis) passes between the pterygoid muscles, where it is joined by the chorda tympani (a branch of the n. intermedius); it then runs downward and forward toward the Tongue, giving off its terminal branch—the sublingual nerve (n. sublingualis)—which innervates the mucous membrane of the floor of the Oral Cavity and the Gums.

The lingual nerve gives off the following branches:

✵ Branches of the faucial isthmus (rr. isthmi faucium) to the faucial isthmus and the palatine tonsil;

✵ Lingual branches (rr. linguales) to the mucous membrane of the anterior 2/3 of the tongue, containing taste fibers from the chorda tympani.

✵ Ganglionic branches (rr. ganglionares) to the submandibular and sublingual ganglia, containing parasympathetic preganglionic fibers (from the chorda tympani) and forming their parasympathetic roots.

Submandibular and sublingual ganglia

(Fig. 35, 35a) (ganglia submandibulare et sublinguale)

The three roots of these ganglia are analogous:

Radix parasympathica — chorda tympani;

Radix sympathica — postganglionic sympathetic fibers from the facial plexus;

Radix sensoria — rr. ganglionares from the lingual nerve.

The sublingual ganglion is inconstant. The branches of the ganglia are glandular branches (rr. glandulares) containing general sensory, postganglionic parasympathetic (secretory), and sympathetic fibers to the submandibular and sublingual glands.

Fig. 35. Branches of the mandibular nerve (schematic)

1 - sensory root (radix sensoria);

2 - motor root (radix motoria);

3 - trigeminal ganglion (ganglion trigeminale);

4 - ophthalmic nerve (n. ophthalmicus);

5 - maxillary nerve (n. maxillaris);

6 - mandibular nerve (n. mandibularis);

7 - parotid gland (glandula parotidea);

8 - otic ganglion (ganglion oticum);

9 - Muscles of Mastication (mm. masticatores);

10 - tongue (lingua);

11 - sublingual gland (glandula sublingualis),

12 - submandibular gland (glandula submandibularis);

13 - submandibular ganglion (ganglion submandibularis);

14 - teeth (dentes);

15 - gingiva, gums (gingiva);

16 - mylohyoid muscle (m. mylohyoideus);

17 - anterior belly of digastric muscle (venter anterior m. digastrici);

18 - auriculotemporal nerve (n. auriculotemporalis);

19 - lingual nerve (n. lingualis);

20 - sublingual branch (r. sublingualis);

21 - buccal nerve (n. buccalis);

22 - inferior alveolar nerve (n. alveolaris inferior);

23 - mental nerve (n. mentalis);

24 - meningeal branch of mandibular nerve (r. meningeus n mandihularis);

25 - inferior dental plexus (plexus dentalis inferior);

26 - motor branches to muscles derived from the 1st pharyngeal arch;

27 - mylohyoid nerve (n. mylohyoideus);

28 - preganglionic parasympathetic fibers from inferior salivatory nucleus (n. petrosus minor);

29 - postganglionic parasympathetic fibers from otic ganglion;

30 - preganglionic parasympathetic fibers from superior salivatory nucleus (chorda tympani);

31 - postganglionic parasympathetic fibers to the Salivary Glands

✵ Communicating branches with the Hypoglossal nerve (rr. communicantes cum nervo hypoglosso).

6. The inferior alveolar nerve (n. alveolaris inferior) is the largest mixed nerve, whose motor branches diverge before entering the mandibular canal (canalis mandibulae) as the mylohyoid nerve (n. mylohyoideus). This nerve innervates the muscle of the same name and the anterior belly of the digastric muscle (m. digastricus).

The inferior alveolar nerve passes through the mandibular canal (canalis mandibulae), giving off branches that form the inferior dental plexus (plexus dentalis inferior). From this plexus, inferior dental and gingival branches (rr. dentales et gingivales inferiores) extend to the teeth and the buccal surface of the gums. Upon exiting the canal through the mental foramen (at the level of the 1st premolar), the nerve is referred to as the mental nerve (n. mentalis). It innervates the skin of the chin and the lower lip (rr. mentales et labiales).

Otic ganglion (ganglion oticum) (Fig. 35 b)

This ganglion is located medial to the mandibular nerve (n. mandibularis) and inferior to the oval foramen.

Roots of the ganglion:

Radix parasympathica — lesser petrosal nerve (n. petrosus minor) — preganglionic parasympathetic fibers from the inferior salivatory nucleus (IX cranial nerve).

Radix sympathica — postganglionic sympathetic fibers from the middle meningeal plexus (plexus meningeus medius);

Radix sensoria — ganglionic branches of the mandibular nerve (rr. ganglionares), or a branch from the auriculotemporal nerve.

Through communicating branches with the auriculotemporal nerve, the otic ganglion supplies its parotid branches (rr. parotidei) with postganglionic secretory fibers that innervate the parotid gland.

Fig. 35 a. Submandibular ganglion, its roots and branches (schematic):

1 - superior salivatory nucleus (nuc. salivatorius superior);

2 - chorda tympani;

3 - lingual nerve (n. lingualis);

4 - superior cervical ganglion of the sympathetic trunk (ganglion cervicale superius trunci sympathici);

5 - intermediolateral nucleus (nuc. intermediolateralis);

6 - submandibular ganglion (ganglion submandibulare);

7 - facial plexus (plexus facialis);

8 - submandibular gland (glandula submandibularis);

9 - sublingual gland (glandula sublingualis)

Fig. 35 b. Otic ganglion, roots, branches, right-side topography, lateral view (schematic):

1 - Glossopharyngeal nerve (n. glossopharyngeus);

2 - tympanic plexus (plexus tympanicus);

3 - lesser petrosal nerve (n. petrosus minor) radix parasympathica;

4 - mandibular nerve (n. mandibularis) — rr. ganglionares — radix sensoria,

5 - nerve to the tensor veli palatini (n. m. tensoris veli palatini);

6 - medial pterygoid nerve (n. pterygoideus medialis);

7 - otic ganglion (ganglion oticum);

8 - middle meningeal plexus (plexus meningeus medius) — radix sympathica;

9 - auriculotemporal nerve (n. auriculotemporalis) to the parotid gland;

10 - nerve to the tensor tympani (n. m. tensoris tympani);

11 - tympanic nerve (n. tympanicus);

12 - superior cervical ganglion of the sympathetic trunk (ganglion cervicale superius tr. sympathici)

The mandibular nerve, similar to the preceding branches of the trigeminal nerve, via communicating branches with the VII and XII cranial nerve pairs, provides proprioceptive innervation to the facial muscles and Muscles of the tongue, while its own branches supply proprioceptive sensitivity to the TEMPOROMANDIBULAR JOINT AND all derivative muscles of the 1st pharyngeal arch.

Innervation of the facial skin (Fig. 36, 37)

The branches of the trigeminal nerve provide both zonal and segmental innervation of the facial skin.

The zones of zonal innervation correspond to the areas of distribution of the cutaneous branches of all three Divisions of the trigeminal nerve (Fig. 36). The Cell bodies of the second-order neurons for facial cutaneous sensitivity are located, as is known, in the pontine (principal) nucleus and the spinal Nucleus of the trigeminal nerve.

Cutaneous sensitivity of the face is conveyed by various fibers of the trigeminal nerve from specific skin areas to specific parts of the aforementioned nuclei. Thus, fibers conducting sensitivity from the medial areas of facial skin terminate in the upper parts of the nuclei, regardless of which trigeminal nerve branch these fibers travel within.

Fibers conducting cutaneous sensitivity from the lateral areas of facial skin terminate in the lower parts of the nuclei (also regardless of their localization in a particular branch of the cranial nerve V). Consequently, segmental Organization is observed in the innervation of the facial skin (Fig. 37), which is typically characteristic of Spinal Nerves.

Fig. 36. Peripheral (zonal) innervation of the scalp skin

1 - frontal nerve (n. frontalis);

2 - supraorbital nerve (n. supraorbitalis);

3 - anterior ethmoidal nerve (n. ethmoidalis anterior);

4 - infraorbital nerve (n. infraorbitalis);

5 - mental nerve (n. mentalis);

6 - great auricular nerve (n. auricularis magnus);*

7 - lesser occipital nerve (n. occipitalis minor);

8 - auriculotemporal nerve (n. auriculotemporalis);*

9 - greater occipital nerve (n. occipitalis major);

10 - buccal nerve (n. buccalis)

* Innervation of the skin of the auricle and the external acoustic meatus is also supplied by the Vagus nerve (not shown in the diagram)

Fig. 37. A — zonal (peripheral) and B — segmental (Zelder's zones) innervation of the scalp by branches of the trigeminal nerve.

B - segmental innervation of the scalp (Zelder's zones)

1 - sensory fibers from the medial regions of the face.

2 - sensory fibers from the lateral regions of the face,

3 - boundary of skin innervation by the trigeminal nerve.

C1, C2, C3, C4 - areas of skin innervation by the corresponding cervical spinal nerves

The segmentary nature of cutaneous innervation may clearly manifest itself when parts of the mentioned nuclei are affected. In this case, the areas of cutaneous sensory disturbances of the face do not coincide with the branching areas of the trigeminal nerve branches in the skin and exhibit a segmental "onion-skin" pattern in the form of arcuate bands (Zelder's zones).