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Download medical textbooks, lectures. Innervation of the eye and orbit Sensitive innervation of the eye

The optic nerve (n. opticus, n. II) is divided into four parts:

intraocular (pars intraocularis) 0.8 mm long,
orbital (pars orbitalis) 24-25 mm long,
channel (pars canalis), not exceeding 8-10 mm and, finally,
intracranial (pars intracranialis) with a length of 10-16 mm.

Contains an average of 1.5 million axons. The diameter of the nerve in the area of the optic nerve head (OND) is 1.5 mm; directly behind the optic disc, due to myelination of nerve fibers, the nerve thickens twice (up to 3.0 mm); in the orbital part its thickness reaches 4.5 mm, which is due to the appearance of perineural membranes.

Of great clinical importance is the difference between the length of the orbital part of the optic nerve (25 mm) and the distance from the posterior pole of the eye to the canalis opticus (18 mm). The S-shaped bend of the optic nerve, caused by a seven-millimeter “reserve,” ensures unhindered movement of the eyeball and also plays a vital damping role in case of injury.

III pair of cranial nerves

The oculomotor nerve (n. oculomotorius, n. III) consists of three components with clearly defined functions.

Somatic efferent(motor) component innervates 4 of the 6 extraocular muscles and the muscle that lifts the upper eyelid, thereby playing a leading role in ensuring involuntary and voluntary eye movements.
Visceral efferent(motor) component provides parasympathetic innervation to the muscle that constricts the pupil (pupillary reflex) and the ciliary muscle (accommodative function).
, providing proprioceptive sensitivity of the innervated muscles. Has 24,000 axons.

Somatic efferent (motor) component starts from a complex of nuclei (two main lateral large cell nuclei, two additional small cell nuclei of Yakubovich-Edinger-Westphal and an additional small cell unpaired accommodative nucleus of Perlia), lying in the central gray matter of the midbrain tegmentum under the bottom of the Sylvian aqueduct at the level of the superior colliculi of the quadrigeminal.

On the coronal section of the trunk, the nuclei of the oculomotor nerve form the letter V, bounded on the inside by the Yakubovich-Edinger-Westphal nucleus and inferiorly laterally by the medial longitudinal fasciculus. The motor and visceral efferent fibers emerging from the nuclear complex are directed forward, in the ventral direction, carry out partial decussation and pass through the red nucleus.

After emerging from the cerebral peduncles in the interpeduncular fossa, the oculomotor nerve passes next to the interpeduncular cistern, the tentorium of the cerebellum, between the posterior cerebral and superior cerebellar arteries.

Intracranial portion n. III is 25 mm. Perforating the dura mater, it penetrates the lateral wall of the cavernous sinus, where it is located above the trochlear nerve. It enters the orbit through the intraconal portion of the superior orbital fissure. Usually at the level of the wall of the cavernous sinus it is divided into superior and inferior branches.

The superior branch ascends outward from the optic nerve and innervates the levator palpebrae superioris and superior rectus muscles. The larger inferior ramus is divided into three branches - the external (parasympathetic root to the ciliary ganglion and fibers for the inferior oblique muscle), middle (inferior rectus) and internal (medial rectus muscle).

Thus, the oculomotor nerve innervates the following muscles:

ipsilateral superior rectus muscle;
muscle that lifts the upper eyelid, on both sides;
ipsilateral medial rectus muscle;
contralateral inferior oblique muscle;
ipsilateral inferior rectus muscle.

Nuclei of the oculomotor nerve
1 - parasympathetic nucleus of Yakubovich-Edinger-Westphal (1` - Perlia nucleus),
2 - nucleus innervating the ipsilateral inferior rectus muscle,
3 - nucleus innervating the ipsilateral superior rectus muscle,
4 - centrally located unpaired caudal nucleus, innervating both muscles that lift the upper eyelid,
5 - nucleus of the contralateral inferior oblique muscle.
6 - nucleus of the ipsilateral medial rectus muscle,
7 - nucleus of the trochlear nerve, innervating the contralateral superior oblique muscle,
8 - nucleus of the abducens nerve, innervating the ipsilateral lateral rectus muscle.

Visceral efferent (motor) component begins in the accessory small-cell lateral nuclei of Yakubovich-Edinger-Westphal. Preganglionic parasympathetic fibers are directed ventrally through the midbrain, interpeduncular fossa, cavernous sinus, superior orbital fissure along with somatic motor fibers.

When passing through the wall of the cavernous sinus, parasympathetic fibers are diffusely dispersed, and after the oculomotor nerve exits the superior orbital fissure, they are grouped in its inferior branch (passing lateral to the inferior rectus muscle and entering the inferior oblique muscle posteriorly-inferiorly). From the lower branch, through the parasympathetic (oculomotor) root, the fibers enter the ciliary ganglion, where the second neuron of the pathway in question lies.

Postganglionic fibers leave the ciliary ganglion as part of 5-6 short ciliary nerves entering the posterior pole of the eye near the optic nerve, mainly on the temporal side. Next, the fibers go forward in the perichoroidal space and end in the ciliary muscle and the muscle that constricts the pupil, with 70-80 separate radial bundles, innervating them sectorally.

Somatic afferent fibers begin from the proprioceptors of the oculomotor muscles and pass as part of the branches of the oculomotor nerve to the cavernous sinus. In the wall of the latter, they enter the optic nerve through connecting branches and then reach the trigeminal ganglion, where the first neurons are located.

II neurons responsible for proprioceptive sensitivity are located in the midbrain nucleus of the V pair (in the midbrain tegmentum).

IV pair of cranial nerves

The nucleus of the trochlear nerve (n. IV) is located in the tegmentum of the midbrain at the level of the lower colliculi of the quadrigeminal in front of the central gray matter and ventral to the Sylvian aqueduct. Adjacent to the nucleus of the trochlear nerve is the complex of nuclei of the oculomotor nerve. Another adjacent structure is the myelinated medial longitudinal fasciculus.

The fibers leaving the nucleus are directed dorsally, bending around the midbrain aqueduct, decussate in the superior medullary velum and emerge on the dorsal surface of the brainstem behind the contralateral inferior colliculus of the midbrain roof (plate quadrigeminal). Thus, the trochlear nerve is the only nerve whose fibers make a complete decussation and exit on the dorsal surface of the brain.

After exiting the brainstem into the enveloping (or quadrigeminal) cistern, the trochlear nerve bends around the lateral side of the cerebral peduncle and turns to the anterior surface of the trunk, located together with the oculomotor nerve between the posterior cerebral and superior cerebellar arteries. Then it enters the lateral wall of the cavernous sinus, where it is located near n. III, V 1, VI.

Due to the longest (~75 mm) intracranial part, the trochlear nerve is more often affected than other cranial nerves in cases of head injury. It enters the orbit through the extraconal portion of the superior orbital fissure, superior to the outside relative to the common tendon ring of Zinn, which is why abduction and drooping of the eyeball can be observed after retrobulbar anesthesia.

In the orbit, the trochlear nerve courses medially between the superior muscle complex and the superior orbital wall and enters the proximal third of the superior oblique muscle. In addition to somatic efferent fibers, it also contains afferent fibers that provide proprioceptive sensitivity to the innervated muscle. The course of these fibers is similar to those located in n. III. Contains the smallest (1500) number of fibers.

VI pair of cranial nerves

The nucleus of the abducens nerve (n. VI) is located in the caudal part of the tegmentum of the pons, almost on the midline under the bottom of the fourth ventricle (diamond-shaped fossa) at the level of the facial tubercle, inward and dorsal to the nucleus of the facial nerve.

The root fibers of the nerve are directed forward, overcome the entire thickness of the pons and emerge on the lower (ventral) surface of the brain in the groove between the pons and the pyramid of the medulla oblongata. Next, the abducens nerve on the side of the basilar artery rises up along the anterior surface of the bridge to the petrous part of the temporal bone, where, together with the inferior petrosal sinus, it appears under the ossified petrosphenoid ligament of Gruber (ligamentum petrosphenoidale), which forms the Dorello canal with the apex of the pyramid of the temporal bone.

Next, the nerve makes a sharp turn forward, pierces the dura mater and enters the cavernous sinus, lying lateral to the internal carotid artery. The abducens nerve is the only nerve fused not with the wall of the cavernous sinus, but with the siphon of the internal carotid artery.

After leaving the sinus, the nerve enters the orbit through the intraconal portion of the superior orbital fissure, located under the oculomotor nerve, and approaches the lateral rectus muscle. Due to the long intracranial part and its location in the narrow bony canal of Dorello, the abducens nerve often suffers in cases of head injury.

V pair of cranial nerves

The trigeminal nerve (n. trigeminus, n. V) is the largest cranial nerve. Consists of sensitive (radix sensoria) and motor (radix motoria) components.

Sensitive part provides tactile, temperature and pain innervation to the fronto-parietal area of the scalp, eyelids, facial skin, mucous membranes of the nose and oral cavity, teeth, eyeball, lacrimal gland, oculomotor muscles, etc.
Motor part b provides innervation to the masticatory muscles. Motor fibers are contained only in the mandibular nerve, which is a mixed nerve. It also provides proprioceptive sensitivity of the masticatory muscles.

Trigeminal ganglion and trigeminal nerve complex

The trigeminal (lunate, Gasserian) node (gangl. trigeminale) provides sensitive innervation of the face. Located in the trigeminal cavity (cavum trigeminale, s. Meckel), formed by the sheets of the dura mater, located on the impression of the same name (impressio trigeminalis) of the apex of the pyramid of the temporal bone.

The relatively large (15-18 mm) trigeminal ganglion is concave posteriorly and convex anteriorly. Three main branches of the trigeminal nerve arise from its anterior convex edge:

ophthalmic (V 1) - leaves the cranial cavity through the superior orbital fissure,
maxillary (V 2) - leaves the cranial cavity through the round hole,
mandibular (V 3) nerve - leaves the cranial cavity through the foramen ovale.

The motor root goes around the trigeminal ganglion from the inside, goes to the foramen ovale, where it joins the third branch of the trigeminal nerve, turning it into a mixed nerve.

The trigeminal ganglion contains pseudounipolar cells, the peripheral processes of which end in receptors that provide touch, pressure, discrimination, temperature and pain sensitivity. The central processes of the cells of the trigeminal ganglion enter the pons at the origin of the last middle cerebellar peduncle and end in the pontine (main sensory) nucleus of the trigeminal nerve (tactile and discriminatory sensitivity), the nucleus of the spinal tract of the trigeminal nerve (pain and temperature sensitivity) and the nucleus of the midbrain tract trigeminal nerve (proprioceptive sensitivity).

Mostovoe(nucl. pontinus n. trigemini), or main sensitive core, is located in the dorsolateral part of the upper part of the pons, lateral to the motor nucleus. The axons of the second, i.e., neurons that form this nucleus, move to the opposite side and, as part of the contralateral medial loop, rise to the ventrolateral nucleus of the thalamus.

Fibers of tactile sensitivity are involved in the formation of the arc of the corneal reflex. Impulses from the mucous membrane of the eye along the optic nerve reach the pontine nucleus of the trigeminal nerve (afferent part of the arch). Then, through the cells of the reticular formation, the impulses switch to the nucleus of the facial nerve and along its axons reach the orbicularis oculi muscle, ensuring reflexive closure of both eyes when one of them is touched (the efferent part of the arch).

Nucleus of the spinal tract(nucl. spinalis n. trigemini) is a downward continuation of the main sensory nucleus throughout the medulla oblongata up to the gelatinous substance (substantia gelatinosa) of the posterior horns of the cervical spinal cord (C 4). Provides pain and temperature sensitivity. Afferent fibers to this nucleus enter the spinal tract of the trigeminal nerve.

The fibers enter the caudal part (pars caudalis) of the spinal tract nucleus of the trigeminal nerve in a strict somatotopic order, located in the form of an inverted projection of the face and head. The pain sensory fibers of the optic nerve (V 1) end most caudally, followed by the fibers of the maxillary nerve (V 2), and finally, the fibers of the mandibular nerve (V 3) are most rostral (cranial).

The spinal tract of the trigeminal nerve is joined by nociceptive fibers from the VII, IX and X pairs of cranial nerves (external ear, posterior third of the tongue, larynx and pharynx). The middle part (pars interpolaris) of the nucleus of the spinal tract receives pain afferentation from the dental pulp. Perhaps the middle and rostral (pars rostralis) parts are also responsible for the perception of pressure and touch.

Axons of second neurons, emerging from the nucleus of the spinal tract, pass to the opposite side in the form of a wide fan-shaped bundle, which, passing through the pons and midbrain to the thalamus, ends in its ventrolateral nucleus.

Axons of the third(thalamic) neurons pass in the posterior leg of the internal capsule to the caudal part of the postcentral gyrus, where the projection center of general sensitivity for the head region is located. The continuation of the pontine nucleus upward is the nucleus of the midbrain tract of the trigeminal nerve (nucl. mesencephalicus n. trigemini). Located lateral to the aqueduct, it is responsible for proprioceptive sensitivity, which comes from baroreceptors and muscle spindle receptors of the masticatory, facial and oculomotor muscles.

Motor, or chewable, core(nucl. motorius n. trigemini s. nucl. masticatorius) is located in the lateral part of the bridge tire, medial to the sensitive one. It receives impulses from both hemispheres, the reticular formation, the red nuclei, the roof of the midbrain, the medial longitudinal fasciculus, the midbrain nucleus, with which the motor nucleus is united by a monosynaptic reflex arc. The axons of the motor nucleus form the motor root, which goes to

masticatory (lateral and medial pterygoid, masseter, temporal) muscles;
tensor tympani muscle;
muscle that strains the velum palatine;
mylohyoid muscle;
anterior belly of the digastric muscle.

Optic nerve (V 1) lies in the wall of the cavernous sinus lateral to the internal carotid artery, between the oculomotor and trochlear nerves. It enters the orbit through the superior orbital fissure, in the lumen of which it is divided into three branches (frontal, lacrimal and nasociliary), providing sensitive innervation to the orbit and the upper third of the face.

The frontal nerve is the largest, located in the orbit between the muscle that lifts the upper eyelid and the periosteum of the upper wall of the orbit, innervates the inner half of the upper eyelid and the corresponding parts of the conjunctiva, forehead, scalp, frontal sinuses and half of the nasal cavity. It leaves the orbit in the form of terminal branches - the supraorbital and supratrochlear nerves.
The lacrimal nerve is the thinnest, lying along the upper edge of the lateral rectus muscle, providing sensitive innervation to the conjunctiva and skin in the area of the lacrimal gland. In addition, it contains postganglionic parasympathetic fibers, which provide reflex lacrimation.
The nasociliary nerve is the only branch of the ophthalmic nerve that enters the orbit through the intraconal portion of the superior orbital fissure. Gives off a small branch that forms the sensitive root of the ciliary ganglion. These fibers pass through the ciliary ganglion in transit without participating in synaptic transmission, since they are peripheral processes of pseudounipolar cells of the trigeminal ganglion. They leave the ciliary ganglion in the form of 5-12 short ciliary nerves, providing sensory innervation to the cornea, iris and ciliary body. These nerves also contain sympathetic vasomotor fibers from the superior cervical ganglion. The nasociliary nerve gives off a number of branches: two long ciliary nerves; anterior and posterior (Luschka nerve) ethmoid nerves (innervation of the nasal mucosa, sphenoid sinus and posterior cells of the ethmoid bone); subtrochlear nerve (innervation of the lacrimal canaliculi, medial ligament of the eyelids, as well as the tip of the nose, which explains the origin of Hutchinson’s symptom (1866) - a rash of vesicles on the wings or tip of the nose with herpes zoster).

As already mentioned, maxillary nerve (V 2) , although it is adjacent to the wall of the cavernous sinus, it still does not lie between the layers of the dura mater that forms its outer wall. At the exit from the round foramen, the maxillary nerve gives off a large (up to 4.5 mm thick) branch - the infraorbital nerve (n. infraorbitalis). Together with the artery of the same name (a. infraorbitalis - branch of a. maxillaris), it enters the orbit through the inferior orbital fissure (in its center), lying under the periosteum.

Next, the nerve and artery lie on the lower wall of the orbit in the groove of the same name (sulcus infraorbitalis), which anteriorly turns into a canal 7-15 mm long, running in the thickness of the orbital surface of the body of the upper jaw almost parallel to the medial wall of the orbit. The canal opens on the face in the area of the canine fossa with the infraorbital foramen (foramen infraorbitale), round in shape, with a diameter of 4.4 mm. In adults, it is located 4-12 mm below the middle of the infraorbital margin (average 9 mm).

It should be noted that, contrary to popular belief, the supra- and infraorbital foramina are not located on the same vertical, called the Hirtle line. In more than 70% of observations, the distance between the infraorbital foramina exceeds by 0.5-1 cm the distance between the supraorbital notches. The opposite situation is typical for those cases when, instead of the supraorbital notch, a foramen of the same name is formed. The vertical distance between the supraorbital notch and the infraorbital foramen averages 44 mm.

From the infratemporal fossa, through the inferior orbital fissure, the zygomatic nerve (n. zygomaticus) also enters the orbit, perforating its periosteum, where it immediately divides into two branches: zygomatico-facialis (r. zygomatico-facialis) and zygomaticotemporal (r. zygomatico-temporalis) ; both nerve trunks enter the canals of the same name in the zygomatic bone to pass to the skin of the zygomatic and temporal regions.

The previously mentioned important anastomosis to the lacrimal nerve, containing postganglionic parasympathetic fibers coming from the pterygopalatine ganglion, departs from the zygomaticotemporal branch in the orbit.

VII pair of cranial nerves

The facial nerve (n. facialis, n. VII) consists of three components, each of which is responsible for a specific type of innervation:

motor efferent innervation of facial muscles originating from the second branchial arch: posterior belly of the digastric, stylohyoid and stapedius muscles, subcutaneous muscle of the neck;
secretory efferent (parasympathetic) innervation of the lacrimal, submandibular and sublingual glands, glands of the mucous membrane of the nasopharynx, hard and soft palate;
gustatory (special afferent) innervation: taste buds of the anterior two-thirds of the tongue, hard and soft palate.

Motor fibers make up the main part of the facial nerve, secretory and gustatory fibers are separated from the motor fibers by an independent sheath and form the intermediate nerve (Wrisberg, Sapolini, n. intermedius). According to the International Anatomical Nomenclature, the intermediate nerve is an integral part of the facial nerve (n. VII).

The motor nucleus of the facial nerve is localized in the ventrolateral part of the tegmentum of the pons on the border with the medulla oblongata. The fibers emerging from the nucleus are first directed medially and dorsally, bending around the nucleus of the abducens nerve (the internal genu of the facial nerve) in the form of a loop. They form the facial hillock, colliculus facialis, at the bottom of the fourth ventricle, then move ventrolaterally to the caudal part of the pons and emerge on the ventral surface of the brain at the cerebellopontine angle.

The nerve root is located next to the root of the VIII pair (vestibular-cochlear nerve), above and lateral to the olive of the medulla oblongata, containing fibers of the intermediate nerve. Next, the facial nerve enters the internal auditory canal and then into the facial nerve canal (fallopian canal of the petrous part of the temporal bone). At the bend of the canal there is a cranked unit (gangl. geniculi).

At the level of the geniculate ganglion, two portions of the facial nerve are separated. The motor fibers pass in transit through the geniculate ganglion, then turn at a right angle posterolaterally, are directed downward and exit the petrous temporal bone through the stylomastoid foramen. After leaving the canal, the facial nerve gives off branches to the stylohyoid muscle and the posterior belly of the digastric muscle, and then forms a plexus in the thickness of the parotid gland.

The innervation of voluntary movements of the facial muscles is carried out by the branches of the parotid plexus:

temporal branches (rr. temporales) - posterior, middle and anterior. They innervate the superior and anterior auricular muscles, the frontal belly of the supracranial muscle, the upper half of the orbicularis oculi muscle and the corrugator muscle;
2-3 zygomatic branches (rr. zygomatici), directed forward and upward, approaching the zygomatic muscles and the lower half of the orbicularis oculi muscle (which must be taken into account when performing akinesia according to Nadbath, O’Brien, van Lindt);
3-4 rather powerful buccal branches (rr. buccales) arise from the upper main branch of the facial nerve and send their branches to the zygomaticus major muscle, the laughter muscle, the buccal muscle, the muscles that elevate and depress the angle of the mouth, the orbicularis oris muscle and the nasal muscle;
marginal branch of the mandible (r. marginalis mandibulae) - innervates the muscles that lower the angle of the mouth and lower lip, as well as the mental muscle;
The cervical branch (r. colli) in the form of 2-3 nerves approaches the subcutaneous muscle of the neck.

Thus, the facial nerve innervates protractors (muscles that close the palpebral fissure) - m. orbicularis oculi, m. procerus, m. corrugator supercilii and one eyelid retractor - m. frontalis. Regulation of voluntary movements of the facial muscles is carried out by the motor cortex (precentral gyrus, gyrus praecentralis) through the corticonuclear tract, passing in the posterior leg of the internal capsule and reaching both the ipsi- and contralateral motor nuclei of the facial nerve.

The part of the nucleus innervating the superior facial muscles receives ipsilateral and contralateral innervation. The portion of the nucleus innervating the inferior facial muscles receives corticonuclear fibers only from the contralateral motor cortex. This fact is of great clinical importance, since central and peripheral paralysis of the facial nerve is accompanied by different clinical pictures.

Topical diagnosis of peripheral facial paralysis (Erb scheme)

Level of nerve damage	Symptom complex
Below the origin of the chorda tympani in the facial nerve canal	Paralysis of the ipsilateral facial muscles; ipsilateral sweating disorder
Above the origin of the chorda tympani and below the stapedius nerve (n. stapedius)	The same + impaired taste sensitivity on the anterior 2/3 of the ipsilateral half of the tongue; decreased salivation by the glands of the affected side
Above the origin of n. stapedius and below the origin of the greater petrosal nerve	Same + hearing loss
Above the origin of the greater petrosal nerve, the region of the geniculate ganglion	The same + decrease in reflex lacrimation; dryness of the ipsilateral half of the nasopharynx; possible vestibular disorders
Above the geniculate ganglion in the internal auditory canal	The same + disappearance of reflexive and affective (crying) lacrimation, hearing impairment in the hyperacusis variant
Internal auditory opening	Peripheral muscle paralysis, decreased or loss of hearing, decreased excitability of the vestibular apparatus; ipsilateral inhibition of tear and saliva production, absence of corneal and brow reflexes, taste disturbance with intact general sensitivity of the tongue (V3)

Unilateral interruption of the corticonuclear pathway leaves the innervation of the frontalis muscle intact (central palsy). A lesion at the level of the nucleus, root or peripheral nerve causes paralysis of all facial muscles of the ipsilateral half of the face - peripheral Bell's palsy.

Peripheral Paralysis Clinic:

pronounced facial asymmetry;
atrophy of the facial muscles;
drooping eyebrow;
smoothness of the frontal and nasolabial folds;
drooping corner of the mouth;
lacrimation;
lagophthalmos;
inability to close lips tightly;
loss of food from the mouth when chewing on the affected side.

The combination of Bell's palsy with dysfunction of the abducens nerve indicates the localization of the pathological focus in the brain stem, with pathology of the vestibulocochlear nerve indicating the presence of a focus in the internal auditory canal.

Central facial palsy occurs as a result of damage to motor cortex neurons or their axons in the corticonuclear tract,located in the posterior leg of the internal capsule and ending in the motor nucleus of the facial nerve. As a result, voluntary contractions of the lower muscles of the contralateral side of the face suffer.Voluntary movements of the muscles of the upper half of the face are preserved due to their bilateral innervation.

Central Paralysis Clinic:

facial asymmetry;
atrophy of the muscles of the lower half of the face on the side opposite to the lesion (as opposed to peripheral paralysis);
no drooping eyebrow (unlike peripheral paralysis);
there is no smoothness of the frontal folds (unlike peripheral paralysis);
preserved conjunctival reflex (due to preserved innervation of the orbicularis oculi muscle);
smoothness of the nasolabial fold on the side opposite to the lesion;
inability to tightly compress the lips on the side opposite to the lesion;
loss of food from the mouth when chewing on the side opposite to the lesion.

Secretory parasympathetic fibers of the facial nerve stimulate the secretion of the submandibular, sublingual and lacrimal glands, as well as the glands of the mucous membrane of the nasopharynx, hard and soft palate.

Efferent parasympathetic fibers originate from a diffuse cluster of neurons in the caudal pons, located under the motor nucleus of the facial nerve. These clusters of neurons are called the superior salivary nucleus (nucl. salivatorius superior) and the lacrimal nucleus (nucl. lacrimalis). The axons of these neurons emerge as part of the intermediate nerve.

P The intermediate nerve leaves the brainstem lateral to the motor root of the facial nerve. In the canal of the facial nerve, the autonomic fibers are divided into two bundles - the greater petrosal nerve (innervates the lacrimal gland, as well as the glands of the nose and palate) and the chorda tympani (innervates the submandibular and sublingual salivary glands).

The chorda tympani also contains sensitive fibers (special taste sensitivity) to the anterior 2/3 of the tongue. Separating from the geniculate ganglion, the greater petrosal nerve goes forward and medially, exits the temporal bone through the cleft of the greater petrosal nerve canal and passes along the groove of the same name to the foramen lacerum. Through it, the nerve reaches the base of the skull, where it connects with the deep petrosal nerve (n. petrosus profundus) from the sympathetic plexus of the internal carotid artery. Their fusion leads to the formation of the nerve of the pterygoid canal (n. canalis pterygoidei, Vidian nerve), passing along the pterygoid canal to the pterygopalatine ganglion (gangl. pterigopalatinum).In the area of the node, the nerve of the pterygoid canal connects with the maxillary nerve (V 2 ).

Postganglionic fibers extending from the neurons of the pterygopalatine ganglion, through the zygomatic and zygomaticotemporal nerves, reach the lacrimal nerve (n. lacrimalis, V 1), which innervates the lacrimal gland. Thus, the parasympathetic innervation of the lacrimal gland occurs independently of the innervation of the eyeball and is largely associated with the innervation of the salivary glands.

The ciliary ganglion plays a critical role in providing sensitive, sympathetic and parasympathetic innervation of the orbital structures. This is a flattened quadrangular formation measuring 2 mm, adjacent to the outer surface of the optic nerve, located 10 mm from the optic opening and 15 mm from the posterior pole of the eye.

The ciliary node has three roots

A well-defined sensory root contains sensory fibers from the cornea, iris and ciliary body, which are part of the nasociliary nerve (V 1);
Parasympathetic (motor) root as part of the external branch of the lower branch n. III reaches the ciliary ganglion, where it forms synaptic transmission and leaves the ciliary ganglion in the form of short ciliary nerves innervating the constrictor pupillary muscle and the ciliary muscle;
The thin sympathetic root of the ciliary ganglion, the structure of which, like the entire sympathetic system of the orbit, has not been fully studied.

The sympathetic innervation of the eye originates in the ciliary spinal center of Budge (lateral horns C8-Th2). The fibers coming out from here rise upward - to the superior cervical ganglion, where they switch to the next neuron, the axons of which form a plexus on the internal carotid artery (plexus caroticus internus). The sympathetic fibers that leave the ICA siphon enter the abducens nerve root, but soon move from it to the nasociliary nerve, with which they enter the orbit through the superior orbital fissure, passing in transit through the ciliary ganglion. As long ciliary nerves, they innervate the dilator muscle and possibly the choroidal vessels. The second portion of sympathetic fibers enters the orbit along with the ophthalmic artery and innervates the superior and inferior muscles of the eyelid cartilage, Müller's orbital muscle, orbital vessels, sweat glands and, possibly, the lacrimal gland.

Innervation of conjugate eye movements

The center of horizontal gaze (pontine gaze center) lies in the paramedian reticular formation of the pons near the nucleus of the abducens nerve. Through the medial longitudinal fasciculus, it sends commands to the ipsilateral nucleus of the abducens nerve and the contralateral nucleus of the oculomotor nerve. As a result, the ipsilateral lateral rectus muscle is commanded to abduct, and the contralateral medial rectus muscle is commanded to adduct. In addition to the extraocular muscles, the medial longitudinal fasciculus connects the anterior and posterior groups of cervical muscles, fibers from the vestibular and basal ganglia, as well as fibers of the cerebral cortex into a single functional complex.

Other potential centers of reflex horizontal conjugal eye movements are fields 18 and 19 of the occipital lobe of the cerebrum, and voluntary movements are field 8 according to Brodmann.

The center of vertical gaze is apparently located in the reticular formation of the periaqueductal gray substance of the midbrain at the level of the superior colliculus and consists of several specialized nuclei.

The prestitial nucleus is located in the posterior wall of the third ventricle, providing upward gaze.
The nucleus of the posterior commissure (Darksevic) is responsible for downward gaze.
The intermediate (interstitial) nucleus of Cajal and the nucleus of Darkshevich provide conjugal rotatory movements of the eyes.

It is possible that conducive vertical eye movements are also provided by neuronal clusters on the anterior border of the superior colliculus. The Darkshevich nucleus and the Cajal nucleus are integration subcortical centers of gaze. From them begins the medial longitudinal fascicle, which includes fibers from the III, IV, VI, VIII, XI pairs of cranial nerves and the cervical plexus.

The motor innervation of the human visual organ is realized through the III, IV, VI and VII pairs of cranial nerves, the sensitive innervation - through the first ( n.ophthalmicus) and partly the second ( n.maxillaris) branches of the trigeminal nerve (V pair of cranial nerves).

Oculomotor nerve (n.oculomotorius III pair of cranial nerves) starts from the nuclei lying at the bottom of the Sylvian aqueduct at the level of the anterior tubercles of the quadrigeminal. These nuclei are heterogeneous and consist of two main lateral ones (right and left), including five groups of large cells ( nuclocilomotoris), and additional small cell ( nucloculomotorius accessorius) - two paired lateral ones (Yakubovich-Edinger-Westphal nucleus) and one unpaired one (Perlia nucleus), located between them (Fig. 3.15). The length of the nuclei of the oculomotor nerve in the anteroposterior direction is 5-6 mm.

From the paired lateral magnocellular nuclei (a-e) fibers depart for three rectus (superior, internal and inferior) and inferior oblique oculomotor muscles, as well as for two portions of the muscle that lifts the upper eyelid, and the fibers innervating the internal and inferior rectus, as well as the inferior oblique muscles immediately cross.

Fibers extending from the paired parvocellular nuclei innervate the sphincter muscle of the pupil (m.sphincter pupillae) through the ciliary ganglion, and those extending from the unpaired nucleus innervate the ciliary muscle.

Through the fibers of the medial longitudinal fasciculus, the nuclei of the oculomotor nerve are connected with the nuclei of the trochlear and abducens nerves, the system of vestibular and auditory nuclei, the nucleus of the facial nerve and the anterior horns of the spinal cord. Thanks to this, coordinated reflex reactions of the eyeball, head, and torso to all kinds of impulses are ensured, in particular vestibular, auditory and visual.

Through the superior orbital fissure, the oculomotor nerve penetrates into the orbit, where, within the muscular funnel, it divides into two branches - superior and inferior. The superior telescopal branch is located between the superior rectus muscle and the muscle that lifts the upper eyelid, and innervates them. The lower, larger branch passes under the optic nerve and is divided into three branches - the external (the root to the ciliary ganglion and fibers for the inferior oblique muscle depart from it), the middle and internal (innervating the inferior and internal rectus muscles, respectively). Spine ( radix oculomotoria) carries fibers from the accessory nuclei of the oculomotor nerve. They impervate the ciliary muscle and the pupillary sphincter.

Trochlear nerve (n.trochlearis, IV pair of cranial nerves) starts from the motor nucleus (length 1.5-2 mm), located at the bottom of the Sylvian aqueduct immediately behind the nucleus of the oculomotor nerve. Penetrates into the orbit through the superior orbital fissure lateral to the muscular infundibulum. Innervates the superior oblique muscle.

Abducens nerve (n.abducens, VI pair of cranial nerves) starts from the nucleus located in the pons at the bottom of the rhomboid fossa. It leaves the cranial cavity through the superior orbital fissure, located inside the muscular funnel between the two branches of the oculomotor nerve. Innervates the external rectus muscle of the eye.

Facial nerve ( n.facialis, n.intermediofacialis, VII pair of cranial nerves) has a mixed composition, that is, it includes not only motor, but also sensory, gustatory and secretory fibers that belong to the intermediate nerve ( n.intermedius Wrisbergi). The latter is closely adjacent to the facial nerve at the base of the brain from the outside and is its dorsal root.

The motor nucleus of the nerve (length 2-6 mm) is located in the lower part of the pons at the bottom of the IV ventricle. The fibers extending from it emerge in the form of a root at the base of the brain in the cerebellopontine angle. Then the facial nerve, together with the intermediate nerve, enters the facial canal of the temporal bone. Here they merge into a common trunk, which further penetrates the parotid salivary gland and divides into two branches forming the parotid plexus - plexus parotideus. Nerve trunks extend from it to the facial muscles, innervating, among other things, the orbicularis oculi muscle.

The intermediate nerve contains secretory fibers for the lacrimal gland. They arise from the lacrimal nucleus, located in the brainstem and through the genu ganglion ( gangl.geniculi) enter the greater petrosal nerve ( n.petrosus major).

The afferent pathway for the main and accessory lacrimal glands begins with the conjunctival and nasal branches of the trigeminal nerve. There are other areas of reflex stimulation of tear production - the retina, the anterior frontal lobe of the brain, the basal ganglion, the thalamus, the hypothalamus and the cervical sympathetic ganglion.

The level of damage to the facial nerve can be determined by the state of tear secretion. When it is not broken, the source is located below gangl.geniculi and vice versa.

Sensitive innervation of the eye and orbital tissues is carried out by the first branch of the trigeminal nerve - optic nerve(n. ophthalmicus), which enters the orbit through the superior orbital fissure and divides into three branches - lacrimal, nasociliary and frontal (Figure 1.22).

Rice. 1.22 – Sensitive nerves of the eye and its appendages

1 – trigeminal nerve; 2 – orbital nerve; 3 – lacrimal nerve; 4 – frontal nerve; 5 – nasociliary nerve; 6 – optic nerve.

The lacrimal nerve innervates the lacrimal gland, the outer parts of the conjunctiva of the eyelids and eyeball, and the skin of the outer upper corner of the eyelid. The nasociliary nerve gives off a branch to the ciliary ganglion, 3-4 long ciliary branches to the eyeball and goes into the nasal cavity. Long ciliary nerves (3-4 in number) approach the posterior part of the eyeball, where they pierce the sclera. In the suprachoroidal space near the ciliary body, they form a dense plexus, the branches of which penetrate the cornea, providing its central parts with sensitive innervation. The frontal nerve is divided into two branches - supraorbital and supratrochlear. All branches, anastomosing among themselves, innervate the middle and inner parts of the skin of the upper eyelid. Ciliary or ciliary node (ganglion ciliare) is a peripheral nerve ganglion. It is located in the orbit on the outside of the optic nerve at a distance of 10-12 mm from the posterior pole of the eye. Sometimes there are 3-4 nodes located around the optic nerve (Figure 1.23).

Rice. 1.23 – Eyelash knot

1 – ophthalmic artery; 2 – ciliary node; 3 – ciliary nerves.

The ciliary ganglion includes sensory fibers of the nasociliary nerve, parasympathetic fibers of the oculomotor nerve, sympathetic fibers of the plexus of the internal carotid artery. 4-6 short ciliary nerves depart from the ciliary ganglion, which penetrate the eyeball through the posterior part of the sclera and supply the eye tissue with sensitive parasympathetic and sympathetic fibers. Parasympathetic fibers innervate the sphincter of the pupil and the ciliary muscle. Sympathetic fibers go to the muscle that dilates the pupil.

Motor nerves include n. oculomotorius, n. trochlearis, n. abducens, n. facialis.

As already mentioned, the oculomotor nerve innervates all the rectus muscles of the eye, except the lateral rectus, the inferior oblique muscle, and the abducens nerve - the lateral rectus muscle. The orbicularis eyelid muscle is innervated by a branch of the facial nerve.

INNERVATION OF THE EYEBALL

The nervous system of the eye is represented by all types of innervation: sensitive, sympathetic and motor. Before penetrating into the eyeball, the anterior ciliary arteries give off a number of branches that form a marginal looped network around the cornea. The anterior ciliary arteries also give off branches that supply the conjunctiva adjacent to the limbus (anterior conjunctival vessels).

The nasociliary nerve gives off a branch to the ciliary ganglion; other fibers are long ciliary nerves. Without interruption in the ciliary ganglion, 3–4 ciliary nerves pierce the eyeball around the optic nerve and along the suprachoroidal space reach the ciliary body, where they form a dense plexus. From the latter, nerve branches penetrate the cornea.

In addition to the long ciliary nerves, the eyeball in the same area includes short ciliary nerves, originating from the ciliary ganglion. The ciliary ganglion is a peripheral nerve ganglion and is about 2 mm in size. It is located in the orbit on the outside of the optic nerve, 8-10 mm from the posterior pole of the eye.

The ganglion, in addition to nasociliary fibers, includes parasympathetic fibers from the plexus of the internal carotid artery.

Short ciliary nerves (4–6), entering the eyeball, provide all eye tissues with sensory, motor and sympathetic fibers.

The sympathetic nerve fibers that innervate the dilator pupil enter the eye as part of the short ciliary nerves, but, joining them between the ciliary ganglion and the eyeball, they do not enter the ciliary ganglion.

In the orbit, the long and short ciliary nerves are joined by sympathetic fibers from the plexus of the internal carotid artery, which are not included in the ciliary ganglion. The ciliary nerves penetrate the eyeball close to the optic nerve. Short ciliary nerves coming from the ciliary ganglion in the amount of 4–6, passing through the sclera, increase to 20–30 nerve trunks, distributed mainly in the vascular tract, and there are no sensory nerves in the choroid, and sympathetic fibers attached to the orbit innervate the iris dilator shells. Therefore, during pathological processes in one of the membranes, for example in the cornea, changes are noted in both the iris and the ciliary body. Thus, the main part of the nerve fibers goes to the eye from the ciliary ganglion, which is located 7-10 mm from the posterior pole of the eyeball and is adjacent to the optic nerve.

The ciliary ganglion includes three roots: sensitive (from the nasociliary nerve - a branch of the trigeminal nerve); motor (formed by parasympathetic fibers passing through the oculomotor nerve) and sympathetic. Four to six short ciliary nerves emerging from the ciliary ganglion branch into another 20–30 branches, which are directed throughout all structures of the eyeball. With them come sympathetic fibers from the superior cervical sympathetic ganglion, which do not enter the ciliary ganglion and innervate the muscle that dilates the pupil. In addition, 3–4 long ciliary nerves (branches of the nasociliary nerve) also pass inside the eyeball, bypassing the ciliary ganglion.

Motor and sensory innervation of the eye and its auxiliary organs. The motor innervation of the human organ of vision is realized through the III, IV, VI, VII pairs of cranial nerves, and the sensory innervation is through the first and partly the second branches of the trigeminal nerve (V pair of cranial nerves).

The oculomotor nerve (the third pair of cranial nerves) begins from the nuclei lying at the bottom of the Sylvian aqueduct at the level of the anterior tubercles of the quadrigeminal. These nuclei are heterogeneous and consist of two main lateral ones (right and left), including five groups of large cells, and additional small-celled ones - two paired lateral ones (Yakubovich-Edinger-Westphal nucleus) and one unpaired one (Perlia nucleus), located between them. The length of the nuclei of the oculomotor nerve in the anteroposterior direction is 5 mm.

From the paired lateral magnocellular nuclei, fibers depart for three rectus (superior, internal and inferior) and inferior oblique oculomotor muscles, as well as for two portions of the muscle that lifts the upper eyelid, with fibers innervating the internal and inferior rectus muscles, as well as the inferior oblique muscle , immediately intersect.

Fibers extending from the paired parvocellular nuclei innervate the sphincter muscle of the pupil through the ciliary ganglion, and fibers extending from the unpaired nucleus innervate the ciliary muscle. Through the fibers of the medial longitudinal fasciculus, the nuclei of the oculomotor nerve are connected with the nuclei of the trochlear and abducens nerves, the system of vestibular and auditory nuclei, the nucleus of the facial nerve and the anterior horns of the spinal cord. Thanks to this, reactions of the eyeball, head, and torso are ensured to all kinds of impulses, in particular vestibular, auditory and visual.

Through the superior orbital fissure, the oculomotor nerve penetrates into the orbit, where, within the muscular funnel, it divides into two branches - superior and inferior. The superior thin branch is located between the superior muscle and the muscle that lifts the upper eyelid, and innervates them. The lower, larger branch passes under the optic nerve and is divided into three branches - the external (the root to the ciliary ganglion and fibers for the inferior oblique muscle depart from it), the middle and internal (innervate the inferior and internal rectus muscles, respectively). The root carries fibers from the accessory nuclei of the oculomotor nerve. They innervate the ciliary muscle and the sphincter of the pupil.

The trochlear nerve (the fourth pair of cranial nerves) arises from the motor nucleus (length 1.5–2 mm), located at the bottom of the aqueduct of Sylvius immediately behind the nucleus of the oculomotor nerve. Penetrates into the orbit through the superior orbital fissure lateral to the muscular infundibulum. Innervates the superior oblique muscle.

The abducens nerve (sixth pair of cranial nerves) originates from the nucleus located in the pons at the bottom of the rhomboid fossa. It leaves the cranial cavity through the superior orbital fissure, located inside the muscular funnel between the two branches of the oculomotor nerve. Innervates the external rectus muscle of the eye.

The facial nerve (the seventh pair of cranial nerves) has a mixed composition, that is, it includes not only motor, but also sensory, gustatory and secretory fibers that belong to the intermediate nerve. The latter is closely adjacent to the facial nerve at the base of the brain from the outside and is its dorsal root.

The motor nucleus of the nerve (length 2–6 mm) is located in the lower part of the pons at the bottom of the fourth ventricle. The fibers extending from it emerge in the form of a root at the base of the brain in the cerebellopontine angle. Then the facial nerve, together with the intermediate nerve, enters the facial canal of the temporal bone. Here they merge into a common trunk, which further penetrates the parotid salivary gland and is divided into two branches that form the parotid plexus. Nerve trunks extend from it to the facial muscles, innervating, among other things, the orbicularis oculi muscle.

The intermediate nerve contains secretory fibers for the lacrimal gland, located in the brainstem, and enters the greater petrosal nerve through the genu ganglion. The afferent pathway for the main and accessory lacrimal glands begins with the conjunctival and nasal branches of the trigeminal nerve. There are other areas of reflex stimulation of tear production - the retina, the anterior frontal lobe of the brain, the basal ganglia, the thalamus, the hypothalamus and the cervical sympathetic ganglion.

The level of damage to the facial nerve can be determined by the state of tear secretion. When it is not broken, the focus is below the knee node, and vice versa.

The trigeminal nerve (the fifth pair of cranial nerves) is mixed, that is, it contains sensory, motor, parasympathetic and sympathetic fibers. It contains nuclei (three sensitive - spinal, pontine, mesencephalon - and one motor), sensory and motor roots, as well as the trigeminal ganglion (on the sensitive root).

Sensitive nerve fibers begin from the bipolar cells of the powerful trigeminal ganglion, 14–29 mm wide and 5–10 mm long.

The axons of the trigeminal ganglion form the three main branches of the trigeminal nerve. Each of them is connected with certain nerve nodes: the ophthalmic nerve - with the ciliary, the maxillary - with the pterygopalatine and the mandibular - with the auricle, submandibular and sublingual.

The first branch of the trigeminal nerve, being the thinnest (2–3 mm), exits the cranial cavity through the orbital fissure. When approaching it, the nerve is divided into three main branches: n. nasociliaris, n. frontalis, n. Lacrimalis.

The nasociliaris nerve, located within the muscular infundibulum of the orbit, in turn, is divided into long ciliary ethmoidal and nasal branches and, in addition, gives off a root to the ciliary ganglion.

Long ciliary nerves in the form of 3-4 thin trunks are directed to the posterior pole of the eye, perforate the sclera around the optic nerve and along the suprachoroidal space are directed anteriorly along with short ciliary nerves extending from the ciliary body and along the circumference of the cornea. The branches of these plexuses provide sensitive and trophic innervation to the corresponding structures of the eye and perilimbal conjunctiva. The rest of it receives sensory innervation from the palpebral branches of the trigeminal nerve.

On the way to the eye, the long ciliary nerves are joined by sympathetic nerve fibers from the plexus of the internal carotid artery, which innervate the pupillary dilator.

Short ciliary nerves (4–6) arise from the ciliary ganglion, the cells of which are connected to the fibers of the corresponding nerves through sensory, motor and sympathetic roots. It is located at a distance of 18–20 mm behind the posterior pole of the eye under the external rectus muscle, adjacent in this zone to the surface of the optic nerve.

Like the long ciliary nerves, the short ones also approach the posterior pole of the eye, perforate the sclera around the circumference of the optic nerve and, increasing in number (up to 20–30), participate in the innervation of the tissues of the eye, primarily its choroid.

Long and short ciliary nerves are a source of sensitive (cornea, iris, ciliary body), vasomotor and trophic innervation.

The final branch of the nasociliaris nerve is the subtrochlear nerve, which innervates the skin in the area of the root of the nose, the inner corner of the eyelids and the corresponding parts of the conjunctiva.

The frontal nerve, being the largest branch of the ophthalmic nerve, after entering the orbit, gives off two large branches - the supraorbital nerve with medial and lateral branches and the supratrochlear nerve. The first of them, having perforated the tarso-orbital fascia, passes through the nasopharyngeal opening of the frontal bone to the skin of the forehead, and the second leaves the orbit at its internal ligament. In general, the frontal nerve provides sensory innervation to the middle part of the upper eyelid, including the conjunctiva, and the skin of the forehead.

The lacrimal nerve, entering the orbit, runs anteriorly over the external rectus muscle of the eye and is divided into two branches - the upper (larger) and the lower. The superior branch, being a continuation of the main nerve, gives branches to the lacrimal gland and conjunctiva. Some of them, after passing through the gland, perforate the tarso-orbital fascia and innervate the skin in the area of the outer corner of the eye, including the area of the upper eyelid.

A small inferior branch of the lacrimal nerve anastomoses with the zygomaticotemporal branch of the zygomatic nerve, which carries secretory fibers for the lacrimal gland.

The second branch of the trigeminal nerve takes part in the sensitive innervation of only the auxiliary organs of the eye through its two branches - the zygomatic and infraorbital nerves. Both of these nerves are separated from the main trunk in the pterygopalatine fossa and penetrate into the orbital cavity through the inferior orbital fissure.

The infraorbital nerve, entering the orbit, passes along the groove of its lower wall and exits through the infraorbital canal onto the facial surface. Innervates the central part of the lower eyelid, the skin of the wings of the nose and the mucous membrane of its vestibule, as well as the mucous membrane of the upper lip, upper gums, alveolar recesses and, in addition, the upper dentition.

The zygomatic nerve in the orbital cavity is divided into two branches: zygomaticotemporal and zygomaticofacial. Having passed through the corresponding channels in the zygomatic bone, they innervate the skin of the lateral forehead and a small area of the zygomatic region.

From the book Eye Diseases: Lecture Notes author Lev Vadimovich Shilnikov

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From the book Emergency Care Directory author Elena Yurievna Khramova

author Vera Podkolzina

From the book Ophthalmologist's Handbook author Vera Podkolzina

From the book First Medical Aid for Children. A guide for the whole family author Nina Bashkirova

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From the book 100% vision. Treatment, recovery, prevention author Svetlana Valerievna Dubrovskaya

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9-11-2012, 12:24

Description

The nervous system of the eye is represented by all types of innervation:

sensitive,
sympathetic
and motor.

Before penetrating into the eyeball, the anterior ciliary arteries give off a number of branches that form a marginal looped network around the cornea. The anterior ciliary arteries also give off branches that supply the conjunctiva adjacent to the limbus (anterior conjunctival vessels).

Nasociliary nerve gives off a branch to the ciliary ganglion, other fibers are long ciliary nerves. Without interruption in the ciliary ganglion, 3-4 ciliary nerves pierce the eyeball around the optic nerve and reach the ciliary body in the suprachoroidal space, where they form a dense plexus. From the latter, nerve branches penetrate the cornea.

In addition to the long ciliary nerves, short nerves enter the eyeball in the same area. ciliary nerves, originating from the ciliary node. The ciliary ganglion is a peripheral nerve ganglion and is about 2 mm in size. It is located in the orbit on the outside of the optic nerve and 8-10 mm from the posterior pole of the eye.

The ganglion, in addition to nasociliary fibers, includes parasympathetic fibers from the plexus of the internal carotid artery.

Short ciliary nerves(4-6), included in the eyeball, provide all eye tissues with sensory, motor and sympathetic fibers.

Sympathetic nerve fibers, innervating the pupillary dilator, enter the eye as part of the short ciliary nerves, but, joining them between the ciliary ganglion and the eyeball, they do not enter the ciliary ganglion.

In the orbit, the long and short ciliary nerves are joined by sympathetic fibers from the plexus of the internal carotid artery, which are not included in the ciliary ganglion. The ciliary nerves penetrate the eyeball close to the optic nerve. Short ciliary nerves coming from the ciliary ganglion in the amount of 4-6, passing through the sclera, increase to 20-30 nerve trunks, distributed predominantly in the vascular tract, and there are no sensory nerves in the choroid, and sympathetic fibers, attached to the orbit, innervate the dilator of the iris shells. Therefore, in case of pathological processes in one of the membranes, for example in the cornea, changes are noted in both the iris and the ciliary body. Thus, the main part of the nerve fibers goes to the eye from the ciliary ganglion, which is located 7-10 mm from the posterior pole of the eyeball and is adjacent to the optic nerve.

The ciliary ganglion consists of three roots:

sensitive (from the nasociliary nerve - a branch of the trigeminal nerve);
motor (formed by parasympathetic fibers passing through the oculomotor nerve)
and sympathetic.

From four to six short ciliary nerves emerging from the ciliary ganglion, they branch into another 20-30 branches, which are directed throughout all structures of the eyeball. With them come sympathetic fibers from the superior cervical sympathetic ganglion, which do not enter the ciliary ganglion and innervate the muscle that dilates the pupil. In addition, 3-4 long ciliary nerves (branches of the nasociliary nerve) also pass inside the eyeball, bypassing the ciliary ganglion.

Motor and sensory innervation of the eye and its auxiliary organs. The motor innervation of the human visual organ is realized through the III, IV, VI, VII pairs of cranial nerves, and the sensory innervation is through the first and partly the second branches of the trigeminal nerve (V pair of cranial nerves).

Oculomotor nerve(third pair of cranial nerves) starts from the nuclei lying at the bottom of the Sylvian aqueduct at the level of the anterior tubercles of the quadrigeminal. These nuclei are heterogeneous and consist of two main lateral ones (right and left), including five groups of large cells, and additional small-celled ones - two paired lateral ones (Yakubovich-Edinger-Westphal nucleus) and one unpaired one (Perlia nucleus), located between them. The length of the nuclei of the oculomotor nerve in the anteroposterior direction is 5 mm.

From the paired lateral magnocellular nuclei, fibers depart for three rectus (superior, internal and inferior) and inferior oblique oculomotor muscles, as well as two portions of the muscle that lifts the upper eyelid, and the fibers innervating the internal and inferior rectus muscles, as well as the inferior oblique muscles, immediately they intersect.

Fibers extending from the paired parvocellular nuclei innervate the sphincter muscle of the pupil through the ciliary ganglion, and fibers extending from the unpaired nucleus innervate the ciliary muscle. Through the fibers of the medial longitudinal fasciculus, the nuclei of the oculomotor nerve are connected with the nuclei of the trochlear and abducens nerves, the system of vestibular and auditory nuclei, the nucleus of the facial nerve and the anterior horns of the spinal cord. Thanks to this reactions of the eyeball, head, torso to all kinds of impulses are ensured, in particular vestibular, auditory and visual.

Through the superior orbital fissure, the oculomotor nerve penetrates into the orbit, where, within the muscular funnel, it divides into two branches - superior and inferior. Upper thin branch located between the superior muscle and the muscle that lifts the upper eyelid, and innervates them. Lower, larger branch passes under the optic nerve and is divided into three branches - the external (the root to the ciliary ganglion and fibers for the inferior oblique muscle depart from it), the middle and internal (innervate the inferior and internal rectus muscles, respectively). The root carries fibers from the accessory nuclei of the oculomotor nerve. They innervate the ciliary muscle and the sphincter of the pupil.

Trochlear nerve(the fourth pair of cranial nerves) starts from the motor nucleus (length 1.5-2 mm), located at the bottom of the Sylvian aqueduct immediately behind the nucleus of the oculomotor nerve. Penetrates into the orbit through the superior orbital fissure lateral to the muscular infundibulum. Innervates the superior oblique muscle.

Abducens nerve(sixth pair of cranial nerves) starts from the nucleus located in the pons at the bottom of the rhomboid fossa. It leaves the cranial cavity through the superior orbital fissure, located inside the muscular funnel between the two branches of the oculomotor nerve. Innervates the external rectus muscle of the eye.

Facial nerve(seventh pair of cranial nerves) has a mixed composition, that is, it includes not only motor, but also sensory, gustatory and secretory fibers that belong to the intermediate nerve. The latter is closely adjacent to the facial nerve at the base of the brain from the outside and is its dorsal root.

The motor nucleus of the nerve (length 2-6 mm) is located in the lower part of the pons at the bottom of the fourth ventricle. The fibers extending from it emerge in the form of a root at the base of the brain in the cerebellopontine angle. Then the facial nerve and the intermediate nerve enter the facial canal of the temporal bone. Here they merge into a common trunk, which further penetrates the parotid salivary gland and is divided into two branches that form the parotid plexus. Nerve trunks extend from it to the facial muscles, innervating, among other things, the orbicularis oculi muscle.

Intermediate nerve contains secretory fibers for the lacrimal gland, located in the brain stem, and through the genu ganglion they enter the greater petrosal nerve. The afferent pathway for the main and accessory lacrimal glands begins with the conjunctival and nasal branches of the trigeminal nerve. There are other areas of reflex stimulation of tear production - the retina, the anterior frontal lobe of the brain, the basal ganglion, the thalamus, the hypothalamus and the cervical sympathetic ganglion.

The level of damage to the facial nerve can be determined by the state of tear secretion. When it is not broken, the focus is below the knee node, and vice versa.

Trigeminal nerve(fifth pair of cranial nerves) is mixed, i.e. it contains sensory, motor, parasympathetic and sympathetic fibers. It contains nuclei (three sensitive - spinal, pontine, midbrain - and one motor), sensory and motor roots, as well as the trigeminal ganglion (on the sensitive root).

Sensitive nerve fibers begin from the bipolar cells of the powerful trigeminal ganglion, 14-29 mm wide and 5-10 mm long.

The axons of the trigeminal ganglion form the three main branches of the trigeminal nerve. Each of them is associated with certain nerve nodes:

optic nerve - with ciliary nerve,
maxillary - with pterygopalatine
and mandibular - with the ear, submandibular and sublingual.

The first branch of the trigeminal nerve, being the thinnest (2-3 mm), exits the cranial cavity through the orbital fissure. When approaching it, the nerve is divided into three main branches: n. nasociliaris, n. frontalis, n. Lacrimalis.

Nerve nasociliaris, located within the muscular funnel of the orbit, in turn, is divided into long ciliary ethmoidal and nasal branches and, in addition, gives off a root to the ciliary ganglion.

Long ciliary nerves in the form of 3-4 thin trunks, they are directed to the posterior pole of the eye, perforate the sclera in the circumference of the optic nerve and along the suprachoroidal space are directed anteriorly along with short ciliary nerves extending from the ciliary body and along the circumference of the cornea. The branches of these plexuses provide sensory and trophic innervation corresponding structures of the eye and perilimbal conjunctiva. The rest of it receives sensory innervation from the palpebral branches of the trigeminal nerve.

On the way to the eye, the long ciliary nerves are joined by sympathetic nerve fibers from the plexus of the internal carotid artery, which innervate the pupillary dilator.

Short ciliary nerves(4-6) originate from the ciliary ganglion, the cells of which are connected to the fibers of the corresponding nerves through the sensory, motor and sympathetic roots. It is located at a distance of 18-20 mm behind the posterior pole of the eye under the external rectus muscle, adjacent in this zone to the surface of the optic nerve.

Like the long ciliary nerves, the short ones also approach the posterior pole of the eye, perforate the sclera around the circumference of the optic nerve and, increasing in number (up to 20-30), participate in the innervation of the tissues of the eye, primarily its choroid.

Long and short ciliary nerves are a source of sensitive (cornea, iris, ciliary body), vasomotor and trophic innervation.

The terminal branch of the nasociliaris nerve is infratrochlear nerve, which innervates the skin in the area of the root of the nose, the inner corner of the eyelids and the corresponding parts of the conjunctiva.

Frontal nerve, being the largest branch of the ophthalmic nerve, after entering the orbit it gives off two large branches - the supraorbital nerve with medial and lateral branches and the supratrochlear nerve. The first of them, having perforated the tarso-orbital fascia, passes through the nasopharyngeal opening of the frontal bone to the skin of the forehead, and the second leaves the orbit at its internal ligament. In general, the frontal nerve provides sensory innervation to the middle part of the upper eyelid, including the conjunctiva, and the skin of the forehead.

Lacrimal nerve, entering the orbit, goes anteriorly over the external rectus muscle of the eye and is divided into two branches - the upper (larger) and lower. The superior branch, being a continuation of the main nerve, gives branches to the lacrimal gland and conjunctiva. Some of them, after passing through the gland, perforate the tarso-orbital fascia and innervate the skin in the area of the outer corner of the eye, including the area of the upper eyelid. A small inferior branch of the lacrimal nerve anastomoses with the zygomaticotemporal branch of the zygomatic nerve, which carries secretory fibers for the lacrimal gland.

Infraorbital nerve, entering the orbit, passes along the groove of its lower wall and exits through the infraorbital canal to the facial surface. Innervates the central part of the lower eyelid, the skin of the wings of the nose and the mucous membrane of its vestibule, as well as the mucous membrane of the upper lip, upper gums, alveolar recesses and, in addition, the upper dentition.

Zygomatic nerve in the orbital cavity it is divided into two branches: zygomaticotemporal and zygomaticofacial. Having passed through the corresponding channels in the zygomatic bone, they innervate the skin of the lateral forehead and a small area of the zygomatic region.