12 cranial nerves. IX pair of cranial nerves - glossopharyngeal nerve. Tenth nerve - n. vagus

The person has 12 pairs cranial nerves (see diagrams below). Scheme of localization of the nuclei of cranial nerves: anteroposterior (a) and lateral (b) projections
The red color indicates the nuclei of the motor nerves, blue - sensory, green - the nuclei of the vestibulocochlear nerve

Olfactory, visual, vestibulocochlear - nerves of highly organized specific sensitivity, which in their own way morphological features represent, as it were, the peripheral parts of the central nervous system.

The article below will list all 12 pairs of cranial nerves, information about which will be accompanied by tables, diagrams and figures.

For more convenient navigation according to the article, there is a picture with clickable links above: just click on the name of the pair of CNs you are interested in and you will immediately be transferred to information about it.

12 pairs of cranial nerves

1 pair of cranial nerves - olfactory (nn. olfactorii)

2 pair of cranial nerves - visual (n. opticus)

With damage to the 2nd pair of cranial nerves, various types of visual impairment can be observed, shown in the figure below.

Any pathology from optic nerve requires mandatory eye examination, possible results which is shown in the figure below.

Fundus examination

3 pair of cranial nerves - oculomotor (n. oculomotorius)

Innervation of the muscles of the eye

The 3rd pair of cranial nerves is involved in the innervation of the muscles involved in the movement of the eye.

- this is a complex reflex act, in which not only 3 pairs, but also 2 pairs of cranial nerves participate. The diagram of this reflex is shown in the figure above.

4 pair of cranial nerves - block (n. trochlearis)

5 pair of cranial nerves - trigeminal (n. trigeminus)

The dendrites of sensitive cells form three nerves along their course (see the innervation zones in the figure below):

• orbital- (zone 1 in the figure),
• maxillary- (zone 2 in the figure),
• mandibular- (zone 3 in the figure).

From skull n. ophthalmicus exits through fissura orbitalis superior, n. maxillaris - through foramen rotundum, n. mandibularis - through the foramen ovale. As part of one of the branches n. mandibularis, which is called n. lingualis, and chorda tympani taste fibers are suitable for the sublingual and mandibular glands.

When involved in the process of the trigeminal node, all types of sensitivity suffer. This is usually accompanied by excruciating pain and the appearance of herpes zoster on the face.

When involved in pathological process core n. trigeminus, located in the spinal tract, the clinic is accompanied by dissociated anesthesia or hypesthesia. At partial lesion segmental annular zones of anesthesia are noted, known in medicine under the name of the scientist who discovered them " Zelder zones" (see diagram). When the upper parts of the nucleus are affected, the sensitivity around the mouth and nose is disturbed; lower - outer parts of the face. Processes in the nucleus are usually not accompanied by pain.

6 pair of cranial nerves - abducens (n. abducens)

Abducens nerve (n. abducens) - motor. The nucleus of the nerve is located in lower section bridge, under the bottom of the fourth ventricle, laterally and dorsally from the dorsal longitudinal bundle.

Damage to the 3rd, 4th, and 6th pairs of cranial nerves causes total ophthalmoplegia. With paralysis of all the muscles of the eye, there is external ophthalmoplegia.

The defeat of the above pairs, as a rule, is peripheral.

Eye innervation

Without the friendly functioning of several components of the muscular apparatus of the eye, it would be impossible to carry out the movements of the eyeballs. The main formation, thanks to which the eye can move, is the dorsal longitudinal bundle of fasciculus longitudinalis, which is a system that connects the 3rd, 4th and 6th cranial nerves with each other and with other analyzers. Cells of the nucleus of the dorsal longitudinal bundle (Darkshevich) are located in the legs big brain laterally from the cerebral aqueduct, on the dorsal surface in the region of the posterior commissure of the brain and frenulum. The fibers go down along the aqueduct of the large brain to the rhomboid fossa and on their way approach the cells of the nuclei of 3, 4 and 6 pairs, making a connection between them and a coordinated function. eye muscles. The composition of the dorsal bundle includes fibers from the cells of the vestibular nucleus (Deiters), which form ascending and descending paths. The first are in contact with the cells of the nuclei of 3, 4 and 6 pairs, the descending branches stretch down, pass in the composition, which end at the cells of the anterior horns, forming tractus vestibulospinalis. The cortical center, which regulates voluntary gaze movements, is located in the region of the middle frontal gyrus. The exact course of the conductors from the cortex is unknown; apparently, they go to the opposite side to the nuclei of the dorsal longitudinal bundle, then along the dorsal bundle to the nuclei of these nerves.

Through the vestibular nuclei, the dorsal longitudinal bundle is connected with the vestibular apparatus and the cerebellum, as well as with the extrapyramidal part of the nervous system, through the tractus vestibulospinalis - with the spinal cord.

7 pair of cranial nerves - facial (n. facialis)

Topography scheme facial nerve presented above.

Intermediate nerve (n. intermedius)

The intermediate nerve is essentially part of the facial.

With damage to the facial nerve, or rather its motor roots, there is paralysis of the mimic muscles of the peripheral type. The central type of paralysis is a rare phenomenon and is observed when the pathological focus is localized in, in particular, in the precentral gyrus. The differences between the two types of mimic muscle paralysis are shown in the figure above.

8 pair of cranial nerves - vestibulocochlear (n. vestibulocochlearis)

The vestibulocochlear nerve anatomically has two roots with completely different functional abilities (this is reflected in the name of the 8th pair):

1. pars cochlearis, performing the auditory function;
2. pars vestibularis, which performs the function of a static feeling.

Pars cochlearis

Other names for the root: "lower cochlear" or "cochlear part".

VII pair - facial nerve (n. Facialis). It is a mixed nerve. It contains motor, parasympathetic and sensory fibers, the last two types of fibers are isolated as an intermediate nerve.

The motor part of the facial nerve provides innervation to all facial muscles of the face, muscles auricle, skull, posterior belly of the digastric muscle, stapedius muscle and subcutaneous muscle of the neck.

In the facial canal, a number of branches depart from the facial nerve.

1. The large stony nerve from the geniculate node on the outer base of the skull connects with the deep stony nerve (a branch of the sympathetic plexus of the internal carotid artery) and forms the nerve of the pterygoid canal, which enters the pterygopalatine canal and reaches the pterygopalatine node. The connection of the large stony and deep stony nerves is the so-called vidian nerve. The nerve contains preganglionic parasympathetic fibers to the pterygopalatine ganglion, as well as sensory fibers from the cells of the knee ganglion. When it is damaged, a peculiar symptom complex occurs, known as neuralgia of the vidian nerve (File's syndrome). The greater stony nerve innervates lacrimal gland. After a break in the pterygopalatine node, the fibers go as part of the maxillary and further zygomatic nerves, anastomose with the lacrimal nerve, which approaches the lacrimal gland. With damage to the large stony nerve, dryness of the eye occurs due to a violation of the secretion of the lacrimal gland, with irritation - lacrimation.

2. The stapedial nerve enters the tympanic cavity and innervates the stapedial muscle. With the tension of this muscle, conditions are created for the best audibility. If innervation is disturbed, paralysis of the stapedius muscle occurs, as a result of which the perception of all sounds becomes sharp, causing painful, discomfort(hyperacusia).

3. The tympanic string separates from the facial nerve in the lower part of the facial canal, enters the tympanic cavity and through the stony-tympanic fissure exits to the outer base of the skull and merges with the lingual nerve. At the point of intersection with the lower alveolar nerve, the drum string gives off a connecting branch to the ear node, in which motor fibers pass from the facial nerve to the muscle that lifts the soft palate.

The drum string transmits taste stimuli from the anterior two-thirds of the tongue to the knee node, and then to the nucleus of the solitary pathway, to which the taste fibers of the glossopharyngeal nerve approach. As part of drum string secretory salivary fibers also pass from the superior salivary nucleus to the submandibular and sublingual salivary glands, previously interrupted in the submandibular and sublingual parasympathetic nodes.

With damage to the facial nerve, the asymmetry of the face immediately attracts attention. Usually mimic muscles are examined during motor load. The subject is offered to raise his eyebrows, frown them, close his eyes. Pay attention to the severity of the nasolabial folds and the position of the corners of the mouth. They ask you to show your teeth (or gums), puff out your cheeks, blow out a candle, and whistle. A number of tests are used to detect mild muscle paresis.

Blink test: eyes blink asynchronously due to slow blinking on the side of the paresis.

Eyelid vibration test: at closed eyes vibration of the eyelids is either reduced or absent on the side of the paresis, which is determined by a light touch of the fingers on the closed eyelids at the outer corners of the eye (especially when pulling the eyelids backwards).

Orbicularis oculi muscle test: on the side of the lesion, the strip of paper is held weaker by the corner of the lips.

Eyelash symptom: on the affected side, with the eyes closed as much as possible, the eyelashes are visible better than on the healthy one, due to insufficient closure of the orbicular muscle of the eye.

For the differentiation of central and peripheral paresis, the study of electrical excitability, as well as electromyography, is important.

The loss of taste sensitivity is called ageusia, its decrease is called hypogeusia, the increase in taste sensitivity is called hypergeusia, its perversion is called parageusia.

Damage symptoms. With damage to the motor part of the facial nerve, peripheral paralysis of the facial muscles develops - the so-called prosoplegia. Facial asymmetry occurs. The entire affected half of the face is motionless, mask-like, the folds of the forehead and nasolabial fold are smoothed out, the palpebral fissure expands, the eye does not close (lagophthalmos - hare's eye), the corner of the mouth drops. When wrinkling the forehead, folds do not form. When trying to close the eye, the eyeball turns upward (Bell's phenomenon). There is increased lacrimation. At the heart of paralytic lacrimation is the constant irritation of the mucous membrane of the eye with a stream of air and dust. In addition, as a result of paralysis of the circular muscle of the eye and insufficient fit of the lower eyelid to the eyeball, a capillary gap is not formed between the lower eyelid and the mucous membrane of the eye, which makes it difficult for the tear to move to the lacrimal canal. Due to the displacement of the opening of the lacrimal canal, the absorption of tears through the lacrimal canal is impaired. This is facilitated by paralysis of the circular muscle of the eye and the loss of the blinking reflex. Constant irritation of the conjunctiva and cornea with a stream of air and dust leads to the development inflammatory phenomena- conjunctivitis and keratitis.

For medical practice, it is important to determine the location of the lesion of the facial nerve. In the event that the motor nucleus of the facial nerve is affected (for example, with the pontine form of poliomyelitis), only paralysis of the facial muscles occurs. If the nucleus and its radicular fibers suffer, the nearby pyramidal path is often involved in the process and, in addition to paralysis of the facial muscles, central paralysis (paresis) of the limbs of the opposite side occurs (Miyar-Gubler syndrome). With simultaneous damage to the nucleus of the abducens nerve, convergent strabismus occurs on the side of the lesion or gaze paralysis towards the focus (Fauville's syndrome). If at the same time sensitive pathways at the level of the nucleus suffer, then hemianesthesia develops on the side opposite to the focus. If the facial nerve is affected at the point of its exit from brain stem in the cerebellopontine angle, which is often the case with inflammatory processes in this area (arachnoiditis cerebellopontine angle) or acoustic neuroma, then paralysis of facial muscles is combined with symptoms of damage to the auditory (hearing loss or deafness) and trigeminal (lack of corneal reflex) nerves. Since the conduction of impulses along the fibers of the intermediate nerve is disrupted, dryness of the eye (xerophthalmia) occurs, taste is lost in the anterior two-thirds of the tongue on the side of the lesion. In this case, xerostomia should develop, but due to the fact that other salivary glands are functioning, dryness in the oral cavity is not noted. There is also no hyperacusis, which theoretically exists, but due to the combined damage to the auditory nerve, it is not detected.

Damage to the nerve in the facial canal up to its knee above the origin of the large stony nerve leads, along with mimic paralysis, to dry eyes, taste disorder and hyperacusis. If the nerve is affected after the departure of the large stony and stirrup nerves, but above the discharge of the tympanic string, then mimic paralysis, lacrimation and taste disorders are determined. With the defeat of the VII pair in the bone canal below the discharge of the tympanic string or at the exit from the stylomastoid foramen, only mimic paralysis with lacrimation occurs. The most common lesions of the facial nerve at the exit from the facial canal and after exiting the skull. Perhaps bilateral damage to the facial nerve, and even recurrent.

In cases where the cortical-nuclear pathway is affected, paralysis of the facial muscles occurs only in the lower half of the face on the side opposite to the lesion. Hemiplegia (or hemiparesis) often occurs on this side. The peculiarities of paralysis are explained by the fact that the part of the nucleus of the facial nerve, which is related to the innervation of the muscles of the upper half of the face, receives bilateral cortical innervation, and the rest - one-sided.

VIII pair - vestibulocochlear nerve (n. vestibulocochlea-ris). Consists of two roots: lower - cochlear and upper - pre-door Symptoms of the lesion. Hearing loss, increased perception of sounds, ringing, tinnitus, auditory hallucinations. After that, hearing acuity is determined. With a decrease (hypacusia) or loss (anacusia) of hearing, it is necessary to determine whether this depends on the damage to the sound-conducting (external auditory canal, middle ear) or sound-perceiving (organ of Corti, cochlear part of the VIII nerve and its nucleus) apparatus. To distinguish between a lesion of the middle ear and a lesion of the cochlear part of the VIII nerve, tuning forks (Rinne and Weber's technique) or audiometry are used. Since the peripheral auditory apparatus turns out to be communicating with both hemispheres of the brain, then the defeat of the auditory conductors above the anterior and posterior auditory nuclei does not cause loss of auditory functions. Unilateral hearing loss or deafness is possible only with damage to the receptor hearing aid, cochlear part of the nerve and its nuclei. In this case, there may be symptoms of irritation (sensation of noise, whistling, buzzing, cod, etc.). When the cortex is irritated temporal lobe brain (for example, with tumors), auditory hallucinations may occur.

The vestibular part (pars vestibularis).

Damage symptoms. The defeat of the vestibular apparatus - the labyrinth, the vestibular part of the VIII nerve and its nuclei - leads to three characteristic symptoms: dizziness, nystagmus and impaired coordination of movements. Conscious and automatic orientation in space is disturbed: the patient has false sensations of displacement of his own body and surrounding objects. Dizziness often occurs in attacks, reaches a very strong degree, may be accompanied by nausea, vomiting .. Rarely, nystagmus is expressed when looking directly; usually it is better detected when looking to the side. Irritation of the vestibular part of the VIII nerve and its nuclei causes nystagmus in the same direction. Shutdown vestibular apparatus leads to nystagmus in the opposite direction.

The defeat of the vestibular apparatus is accompanied by incorrect jet movements, a violation of the normal tone of the muscles and their antagonists. Movements are deprived of proper regulatory influences, hence the discoordination of movements (vestibular ataxia). Appears wobbly gait, the patient deviates towards the affected labyrinth, and in this direction he often falls.

Dizziness, nystagmus, and ataxia can be observed with damage not only to the vestibular apparatus, but also to the cerebellum; therefore, it is important to differentiate labyrinthine lesions from similar cerebellar symptoms. Diagnosis is based on the following data: 1) dizziness with labyrinthitis is extremely intense; 2) in the Romberg test, the body leans to the side with closed eyes, and there is a dependence on the position of the head and the affected labyrinth; 3) ataxia is always general, that is, it is not limited to only one limb or limbs of one side, it is not accompanied by intentional trembling, as is observed with cerebellar ataxia; 4) nystagmus with a labyrinthine lesion is characterized by a clearly expressed fast and slow phase and has a horizontal or rotatory direction, but not a vertical one; 5) labyrinthine lesions are usually associated with symptoms of hearing loss (eg, tinnitus, hearing loss).

2.37 Symptoms of damage to the 9th and 10th pairs of cranial nerves.

Glossopharyngeal and nervus vagus s (n. glossopharyngeus et n. vagus). They have common nuclei, which are laid in the medulla oblongata in one place, therefore they are examined simultaneously.

IX pair - glossopharyngeal nerve (p. glossopharyngeus). Contains 4 types of fibers: sensory, motor, gustatory and secretory. Sensitive innervation of the posterior third of the tongue, soft palate, pharynx, pharynx, anterior surface of the epiglottis, auditory tube and tympanic cavity. The motor fibers innervate the stylo-pharyngeal muscle, which raises the upper part of the pharynx during swallowing.

Parasympathetic fibers innervate the parotid gland.

Damage symptoms. When the glossopharyngeal nerve is affected, taste disorders are observed in the posterior third of the tongue (hypogeusia or ageusia), loss of sensitivity in the upper half of the pharynx; violations motor function are not clinically expressed due to the insignificant functional role of schiloglo-

precise muscle. Irritation of the cortical projection area in the deep structures of the temporal lobe leads to the appearance of false taste sensations (parageusia). Sometimes they can be harbingers (aura) epileptic seizure. Irritation of the IX nerve causes pain in the root of the tongue or tonsil, extending to palatine curtain, throat, ear.

X pair - vagus nerve (p. vagus). Contains sensory, motor and autonomic fibers. Provides sensory innervation of the dura mater of the posterior cranial fossa, rear wall external auditory canal and part of the skin of the auricle, mucous membrane of the pharynx, larynx, upper trachea and internal organs Motor fibers innervate the striated muscles of the pharynx, soft palate, larynx, epiglottis and upper esophagus.

Vegetative (parasympathetic) fibers go to the heart muscle, smooth muscle tissue vessels and internal organs. Impulses traveling through these fibers slow down the heartbeat, dilate blood vessels, constrict the bronchi, and increase intestinal motility. Postganglionic sympathetic fibers from paravertebral cells also enter the vagus nerve. sympathetic nodes and spread along the branches of the vagus nerve to the heart, blood vessels and internal organs.

Damage symptoms. When the periphery of the vagus neuron is damaged, swallowing is disturbed due to paralysis of the muscles of the pharynx and esophagus. There is a hit of liquid food in the nose as a result of paralysis of the palatine muscles, drooping of the soft palate on the affected side. With paralysis, the voice of the ligaments is weakened by the sonority of the voice, with bilateral damage, up to aphonia and suffocation. The symptoms of vagus damage include a disorder of cardiac activity - tachycardia and bradycardia (with irritation). With a unilateral lesion, the s-we are slightly expressed, with a bilateral lesion, pronounced disorders of swallowing, phonation, respiration and heart activity. When the feelings of the branches of the vagus are affected, the feeling of the mucus of the ob-ki of the larynx, pain in the larynx and ear are disturbed. With the defeat of the 9th pair, the taste for bitter and salty in the back of a third of the tongue is lost, as well as the feeling of mucus from the upper part of the pharynx.

Functional types of cranial nerves.

IV. STATEMENT OF NEW MATERIAL.

III. STUDENT KNOWLEDGE CONTROL

II. MOTIVATION OF LEARNING ACTIVITIES

1. The knowledge gained in this lesson is necessary in your educational (in the study of nervous diseases) and practical activities.

2. Based on the knowledge gained in this lesson, you will be able to build your own reflex arcs various kinds reflexes, as well as navigate the topography with I-VI pairs of cranial nerves.

A. Individual tasks for students for oral response at the blackboard (25 minutes).

1. general characteristics terminal brain.

2. Furrows, convolutions, lobes of the telencephalon.

3. Internal structure of the telencephalon.

4. Cavity of the brain.

5. Shells of the brain.

B. Answer the silent cards (written survey):

1. Cerebral hemisphere, upper lateral surface.

2. Furrows and convolutions on the medial and lower (partially) surfaces of the cerebral hemispheres.

3. Furrows and convolutions on the lower surfaces of the cerebral hemispheres.

4. Brain; frontal cut.

5. Brain; horizontal cut.

6. Pathways of reflex movements (diagrams).

Plan:

1. Functional types of cranial nerves.

2. Cranial nerves of I-VI pairs.

12 pairs of cranial nerves leave the brain. Each pair of nerves has its own number and name, they are designated by Roman numerals in order of location.

ChMN have different functions, because. they consist only of motor or sensory, or of two types of nerve fibers (mixed).

Purely motor - III, IV, VI, XI, XII pairs of cranial nerves.

Purely sensitive - I, II, VIII pairs of cranial nerves.

Mixed - V, VII, IX, X pairs of cramps.

I pair - olfactory nerve(n.olfactorius)- represents a collection of thin filaments (olfactory filaments), which are processes of nerve olfactory cells located: in the mucous membrane of the nasal cavity, in the region of the upper nasal passage, superior turbinate, upper part of the nasal septum.

They go through the holes of the cribriform plate into the cranial cavity into the olfactory bulb.

From here, impulses are transmitted along the olfactory brain and the tract to the cerebral cortex. Purely sensitive in function.

II pair – optic nerve (n. opticus)- formed by processes of neurites of the retina, exits the orbit into the cranial cavity through the optic canal. In front of the Turkish saddle, it forms an incomplete decussation (chiasma) of the optic nerves and passes into the optic tract.

The optic tracts approach the lateral geniculate bodies, the thalamic cushions, and the superior colliculus of the midbrain, where the subcortical visual centers are located. Purely sensitive in function.

III pair - oculomotor nerve(n.oculomotorius)- in function motor, with an admixture of parasympathetic fibers.

One part of the nerve originates from the motor nucleus located at the bottom cerebral aqueduct.

The second part of the nerve is from the parasympathetic nucleus of Yakubovich, located in the midbrain.

Passes into the orbit through the upper orbital fissure, where it is divided into 2 branches: upper and lower.

Innervates the muscles of the eye. Parasympathetic fibers innervate the smooth muscles of the eyeball - the muscle that narrows the pupil and the ciliary muscle.

IV couple – trochlear nerve (n. trochlearis)-motor. It starts from the nucleus, located at the bottom of the cerebral aqueduct at the level of the lower mounds of the roof of the midbrain, passes into the orbit through the superior orbital fissure. Innervates the superior oblique muscle of the eye.

V para-trigeminal nerve(n.trigeminus)- mixed.

Sensitive fibers innervates the skin of the face, front of the head, eyes, mucous membranes of the nasal and oral cavities, paranasal sinuses nose.

By the number of innervated areas, it is the main sensory nerve of the head.

Motor fibers - innervate the masticatory muscles; muscles of the bottom of the mouth; a muscle that stretches the soft palate and one of the muscles tympanic cavity.

The main nuclei of the V pair (sensory and motor) are located in the pons in the upper half of the rhomboid fossa.

It comes out of the brain with two roots: motor (smaller) and sensitive (large). Sensory fibers are processes of sensory neurons that form at the top of the pyramid node trigeminal nerve.

The peripheral processes of these cells form the 3 branches of the trigeminal nerve:

1. The first is the optic nerve.

2. The second is the maxillary.

3. The third is the mandibular nerve.

The first branches are purely sensitive in their composition, and the third branch is mixed, because. motor fibers are attached to it.

ophthalmic nerve(n.ophthalmicus) - goes to the orbit through the upper orbital fissure, here it is divided into 3 main branches that innervate the contents of the orbit; eyeball; skin upper eyelid; conjunctiva of the eye; mucous membrane of the upper part of the nasal cavity, frontal, sphenoid sinuses and cells of the ethmoid bone.

The terminal branches, leaving the orbit, innervate the skin of the forehead.

maxillary nerve(n.maxillaris) passes through a round hole into the pterygopalatine fossa, where it gives off branches that go into the oral cavity, nasal cavity and eye socket.

Branches depart from the pterygopalatine node, which innervate the mucous membrane of the soft and hard palate, nasal cavity.

Depart from it: infraorbital and zygomatic nerves, as well as nodal branches to the pterygopalatine node.

Infraorbital nerve - gives off branches for innervation of teeth, gums upper jaw, innervates the skin of the lower eyelid, nose, upper lip.

Zygomatic nerve - gives branches from parasympathetic fibers to the mucous gland, innervates the skin of the temporal, zygomatic and buccal regions.

Mandibular nerve(n.mandibularis) - exits the skull through oval hole and is divided into a number of motor branches to all chewing muscles: the jaw-hyoid muscle; the muscle that strains the soft curtain and to the muscle that strains the tympanic membrane.

The mandibular nerve gives off a number of sensory branches, including large ones: the lingual and inferior alveolar nerves; smaller nerves (lingual, ear-temporal, meningeal).

Small nerves innervate the skin and mucous membrane of the cheeks, part of the auricle, external auditory canal, eardrum, skin temporal region, parotid salivary gland, meninges.

The lingual nerve innervates 2/3 of the tongue and oral mucosa (perceives pain, touch, temperature).

The inferior alveolar nerve enters the canal mandible, innervates the teeth and gums of the lower jaw, then passes through the mental opening, innervates the skin of the chin and lower lip.

VI couple - abducens nerve (n.abducens) - lies in the back of the bridge at the bottom of the IV ventricle. It starts from the brain stem, passes into the orbit through the superior orbital fissure.

Functionally motor.

From the base of the brain (Fig. 309), centrifugal nerves exit from its trunk through various openings of the skull, and centripetal nerves enter it. In view of the more complex structure of the brain, the course of the nerves here does not have such regularity as is observed in the spinal cord. There are 12 pairs of all cranial nerves; on the base of the skull, they are located in the following order, counting from front to back: I - olfactory, II - visual, III - oculomotor, IV - trochlear, V - trigeminal, VI - efferent, VII - facial, VIII - auditory, IX - glossopharyngeal, X - vagus, XI - accessory, XII - hypoglossal nerves.

The exit points of these nerves from the brain and skull are shown in the following table.

As we already know, all spinal nerves are nerves of a mixed nature, while only a part of the cranial nerves are mixed, and most of them are either purely sensory or purely motor. Sensitive cranial nerves (except for pairs I and II), just like the spinal nerves, have their ganglions (ganglia) located not far from the brain, and their fibers begin outside the brain stem from unipolar cells similar to cells of the spinal nodes. The neurites of these cells are sent to the brain stem and there they end in sensitive nuclei, where they switch to other neurons that transmit stimulation in the centripetal direction; dendrites are directed to the periphery. Motor fibers emerge from the motor nuclei of the brain stem.

Olfactory nerve (n. olfactorius) - I pair (Fig. 310). This is a purely sensory nerve, therefore, nerve impulses pass through it from the periphery to the center. Olfactory fibers originate in special nerve olfactory cells in upper section nasal mucosa. From here they are in the form of 20 thin branches - olfactory threads - sent to the cranial cavity through the holes of the perforated plate, ethmoid bone and end in the nuclei of the olfactory bulb. The olfactory bulb is located on the horizontal plate of the ethmoid bone on both sides of the cockscomb. The second neuron begins in the bulb, the fibers of which make up olfactory tract, carrying irritation to the cerebral cortex in the olfactory center in the temporal lobe (hippocampal gyrus).

Optic nerve (n. opticus) - II pair, like the olfactory one, is a purely sensory nerve. Visual fibers begin in special nerve sensitive cells of the retina; from here, the fibers through the visual openings penetrate into the cranial cavity, where they form an incomplete decussation (chyasma) above the Turkish saddle. After crossing, the optic pathway (optic tract), rounding the legs of the brain, goes to the cortex occipital lobe to visual center. At the same time, on its way to the cerebral cortex, the visual pathway is interrupted (switched to the second neuron) in the cushion of the thalamus opticus and in the superior colliculus of the quadrigemina, where the subcortical centers are located.

The oculomotor nerve (n. oculomotorius) - III pair (Fig. 311) - is a motor nerve, it conducts nerve impulses from the center to the periphery. Its fibers begin in the gray matter of the bottom of the cerebral (Sylvian) aqueduct under the anterior tubercles of the quadrigemina. From the brain stem, the nerve appears at the base of the brain between the cerebral peduncles at the anterior edge of the cerebral (varoli) pons, then through the superior orbital fissure, the nerve exits the cranial cavity into the orbit. In the orbit, the nerve supplies motor fibers to all the muscles of the eyeball (except for the superior oblique and external rectus), as well as the muscle that lifts the upper eyelid.

Together with the oculomotor nerve, parasympathetic fibers go, which are separated from it already in the cavity of the orbit and go to the trigeminal ganglion located at outer surface optic nerve. These autonomic fibers innervate two smooth muscles of the eyeball - the constrictor of the pupil and the increase in the convexity of the lens of the eye.

In diseases of the oculomotor nerve, drooping of the eyelid is observed - ptosis, immobility of the eye, pupil dilation and loss of accommodation.

Block nerve (n. trochlearis) - IV pair - thin motor nerve; it begins in the gray matter of the bottom of the cerebral aqueduct at the level of the inferior tubercles of the quadrigemina. The nerve enters the orbit through the superior orbital fissure and innervates there only one trochlear muscle of the eyeball (superior oblique muscle), to which it brings motor impulses from the cerebral cortex.

Trigeminal nerve (n. trigeminus) -V pair (Fig. 310, 311, 312, 312a) - mixed nerve and the thickest of all cranial. It emerges from the cerebral bridge (from the side) with two roots: a thick sensory and a thin motor. The sensitive root carries a large gasser node (ganglion Gasseri), which serves as the beginning of sensitive fibers; it is located on the pyramid temporal bone. This node corresponds to the intervertebral nodes of the spinal nerves (homologous to the ganglion spinale). Three large branches of the trigeminal nerve depart from the Gasser node: the ophthalmic nerve, maxillary and mandibular. The first two branches of the trigeminal nerve are purely sensitive, the motor portion of the trigeminal nerve joins the third. In addition, sympathetic fibers join each of the branches along the way, which terminate in the lacrimal and salivary glands Oh.

The ophthalmic nerve (n. ophthalmicus) enters the cavity of the orbit through the superior orbital fissure, innervates the connective membrane of the eye (conjunctiva), lacrimal sac; then, leaving the orbital cavity, gives BOL windows for the skin of the forehead, scalp, frontal sinus and solid meninges.

The maxillary nerve (n. maxillaris) (Fig. 312a) leaves the cranial cavity through the round opening of the main bone and goes to the pterygopalatine fossa. It supplies the skin of the cheek, the mucous membrane of the hard and soft palate in oral cavity, then innervates the gums and teeth of the upper jaw (upper cellular or upper alveolar nerves - n. alveolare superiores).

Mandibular nerve (n. mandibularis) (Fig. 313) is mixed. It leaves the skull through the foramen ovale and immediately divides into two large branches: the lingual nerve (n. lingualis) and the lower cell (n. alveolaris inferior). The lingual goes to the submandibular region to the tongue, supplying its mucous membrane with sensory fibers, the parasympathetic nerve joins it - the drum string (chorda tympani), through which the lingual nerve innervates the submandibular and sublingual salivary glands; branches from the lingual nerve to the salivary glands contain a ganglion submaxillar. The lower cellular (lower alveolar) enters together with the lower cellular artery into the canal of the lower jaw, during which it gives off sensitive branches to the teeth, gum mucosa. Its final branch - the mental nerve - innervates the skin of the lower jaw with its sensory fibers. The mandibular nerve also supplies the oral mucosa, mandibular joint. With its motor fibers, this nerve supplies all the chewing muscles of the face and the diaphragm of the mouth.

Abducens nerve (n. abducens) - VI pair, this is a purely motor nerve. Its fibers begin at the bottom of the IV ventricle; the nerve exits the trunk behind the brain bridge (between the pyramid and the bridge) and through the upper orbital fissure, together with the oculomotor nerve, enters the orbit and innervates the external abductor muscle of the eye (abducting the eye outward).

Facial nerve (n. facialis) - VII pair (Fig. 314 and 315), it is a mixed nerve (mainly motor). It begins at the bottom of the IV ventricle, exits the brainstem and at the posterior edge of the cerebral bridge (ponto-cerebellar angle), to the side of the VI pair. Upon exiting the brain, it goes along with the auditory nerve through the internal auditory canal to the pyramid of the temporal bone and lies there in a special canal of the facial nerve, and exits the temporal bone on its lower surface through the styloid mastoid opening, then enters the substance of the parotid gland, where it fan-shaped breaks down, forming the so-called large crow's foot, on a series of branches heading towards the face. The facial nerve innervates all the facial muscles of the face, the subcutaneous muscle of the neck (m. platysma), the posterior belly of the digastric muscle. Together with VII nerve the intermediate nerve of Wriesberg emerges from the brain. Its sensitive fibers form a cranked node in the pyramid of the temporal bone, and from there they go to the mucous membrane of the anterior part of the tongue and soft palate. Nerve taste impulses are carried along these fibers centripetally to the brain to the taste center. The parasympathetic secretory fibers of the Wriesberg nerve pass through the aforementioned chorda tympani and innervate the salivary glands (except for the parotid).

Paralysis of the facial nerve leads to a characteristic distortion of the face; at the same time, the eye almost does not close, it lacrimates, the nasolabial fold is smoothed out.

Auditory nerve (n. laeusticus s. n. stato acusticus) - VIII pair, specifically sensitive. It consists of the fibers of the auditory nerve proper (cochlear) and vestibular (balance nerve). The auditory nerve fibers originate in the spiral ganglion located in the cochlea. inner ear(inside the pyramid of the temporal bone), and the vestibular - in the vestibular ganglion, located at the bottom of the internal auditory canal.

Two bundles of fibers depart from the cells of the spiral ganglion: central and peripheral. The fibers of the central bundle are sent to the nuclei in the rhomboid fossa and to the inferior tubercles of the quadrigemina, from where the second neuron carries irritations through the internal brain capsule to the temporal cortex, where the auditory center is located. The fibers of the peripheral bundle penetrate deep into the cochlea to the spiral (Corti) organ, where sound vibrations are perceived. Excitations of the endings of the auditory nerve, which arose in the spiral organ due to air vibrations, reach the cerebral cortex and are perceived by us as sound sensations.

Two bundles of fibers also depart from the cells of the vestibular ganglion - central and peripheral. The fibers of the central bundle go to the nuclei of the rhomboid fossa, and from there the second neuron conducts a nerve impulse to the cerebellum. The fibers of the peripheral bundle carry impulses from the organs of balance - the semicircular canals and the statolithic organ of the inner ear. Nerve impulses from the semicircular canals go centripetally through the vestibular ganglion and the rhomboid fossa to the cerebellum, where complex combinations of excitations perceived by the semicircular canals occur.

Glossopharyngeal nerve (n. glossopharyngeus) - IX pair (Fig. 316), mixed, and sensory fibers predominate in it. Motor fibers begin at the bottom of the IV ventricle and exit the medulla oblongata behind the olive. The beginning of the sensory fibers is the so-called stony knot, which lies under the pyramid of the temporal bone in the jugular foramen, through which the nerve (together with the X and XI pair) leaves the skull. This node is also similar to the intervertebral nodes of the spinal nerves. Sensitive fibers end at the bottom of the IV ventricle near the exit point of the motor fibers; from here the second neuron carries irritations to the cerebral cortex.

After leaving the jugular foramen, the nerve descends, then makes an arc and approaches the root of the tongue; it supplies its posterior third with sensitive and specific taste fibers, and also innervates the mucous membrane of the pharynx, tonsils and palatine arches. From all these places, excitation is sent centripetally to the brain. The motor fibers of the glossopharyngeal nerve supply the muscles of the pharynx.

The glossopharyngeal nerve also contains parasympathetic fibers that separate from it in the form of thin branches; one goes down (Hering's nerve), to the areas of bifurcation of the common carotid artery, the other, originating in the stony node (Jacobson's, or tympanic, nerve - n. tympanicus), carries secretory fibers for the parotid gland.

The glossopharyngeal nerve, together with the vagus and sympathetic nerve on the walls of the pharynx, forms the pharyngeal plexus.

Vagus nerve (n. vagus) - X pair, mixed. It is the longest of all cranial nerves; its area of ​​​​distribution is much wider than all the others, as a result of which it received the name wandering. It comes out of the brain stem with 10-18 roots next to the glossopharyngeal, that is, behind the olives of the medulla oblongata. It leaves the cranial cavity together with the IX and XI pair and the internal jugular vein through the jugular foramen, forming here connections with neighboring nerves (IX and XI); on the neck it forms a bow knot (ganglion nodosum). Going down further to the neck, the vagus nerve passes between the internal jugular vein and the common carotid artery, where it gives branches to the internal organs of the neck (larynx, pharynx, esophagus) and branches (inhibitory) to the heart. Then the nerve in front of the subclavian artery enters the chest cavity, goes around the primary bronchus from front to back, here it gives off branches to the bronchi and lungs; the left vagus nerve lies along the anterior, and the right - along the posterior surface of the esophagus. Further, both nerves pass through the esophagus through the diaphragm into the abdominal cavity. Having passed through the diaphragm, the vagus nerve is part of the sympathetic plexuses, from which branches extend to all organs of the upper and partly lower sections. abdominal cavity. A particularly dense network nerve plexuses the vagus nerve forms on the walls of the esophagus and stomach, from where its fibers go to the celiac (solar) plexus, located on the abdominal aorta behind the stomach, and from there to the spleen, pancreas, kidneys, liver and intestines (to the descending colon).

Motor and parasympathetic fibers of the above IX and X nerves begin at the bottom of the IV ventricle; sensory fibers, which make up the centripetal path of reflexes carried out through these nerves, also end there.

The composition of the vagus nerve is predominantly parasympathetic in nature, centrifugal fibers (motor and secretory), with which it innervates the involuntary muscles respiratory tract, stomach, intestines, heart and glandular apparatus of the respiratory and digestive organs.

The vagus nerve gives sensitive fibers to the mucous membrane of the larynx, pharynx, stomach and intestines.

For innervation of the larynx, the vagus nerve gives two branches: the upper laryngeal nerve (n. laryngeus superior) is predominantly sensitive and the lower laryngeal (n. laryngeus inferior) with motor fibers to the muscles of the larynx, which is the final part of the recurrent branch. The recurrent nerve (n. recurrens) on the right bends around the subclavian artery, on the left - the aortic arch. Branches depart from it to the heart, trachea, esophagus and to the lower part of the pharynx. A sensory nerve runs from the superior laryngeal nerve to the aortic arch, causing a reflex fall blood pressure- Ludwig Zion depressors.

The vagus nerve is the main nerve of the parasympathetic nervous system, to which the third, seventh, and ninth cranial nerves also belong. For the heart, the vagus nerve is an inhibitory nerve, for the intestines it is an accelerator.

Accessory, or willisian, nerve (n. accessorius) - XI pair; it is exclusively a motor nerve. This nerve actually does not even belong to the cranial, its fibers originate in the cells of the anterior horns of the cervical part. spinal cord. The nerve roots, leaving the spinal cord, rise up and through the large occipital foramen enter the cranial cavity; then the accessory nerve, together with the vagus and glossopharyngeal nerves, again exits through the jugular foramen to the neck, where it innervates the sternocleidomastoid and trapezius muscles.

Hypoglossal nerve (n. hypoglossus)-XII pair (Fig. 317); it is also a purely motor nerve, conducting nerve impulses centrifugally. It begins in the lower part of the bottom of the IV ventricle, and leaves the medulla oblongata between the pyramid and the olive with 10-15 roots, which form a common trunk that exits the cranial cavity through the opening of the same name at the base of the articular process of the occipital bone, then arcuately goes to the tongue, innervates the entire its muscles and partially (together with fibers from II and III cervical nerve) some neck muscles.

The first two nerves have significant differences from the rest of the 10 topics, since in fact they are a continuation of the brain, which is formed by protrusion of the cerebral vesicles. In addition, they do not have nodes (nuclei) that other 10 have. The nuclei of the cranial nerves, like other ganglia of the central nervous system, are concentrations of neurons that perform certain functions.

10 pairs, with the exception of the first two, are not formed from two types of roots (anterior and posterior), as is the case with spinal cords, but represent only one root - anterior (in III, IV, VI, XI, XII) or posterior (in V, from VII to X).

The common term for this type of nerve is "cranial nerves", although Russian-language sources prefer to use "cranial nerves". This is not a mistake, but it is preferable to use the first term - in accordance with the international anatomical classification.

All cranial nerves are laid in the embryo already in the second month. At the 4th month of prenatal development, myelination of the vestibular nerve begins - the overlay of myelin fibers. Motor fibers go through this stage earlier than sensory ones. The state of nerves in the postnatal period is characterized by the fact that, as a result, the first two pairs are the most developed, the rest continue to become more complicated. Final myelination occurs at about one and a half years of age.

Classification

Before proceeding to a detailed consideration of each individual pair (anatomy and functioning), it is best to familiarize yourself with them with the help of brief characteristics.

Table 1: Characteristics of 12 pairs

Nerves with sensory fibers

Olfactory begins in the nerve cells of the nasal mucosa, then passes through the cribriform plate into the cranial cavity to the olfactory bulb and rushes into the olfactory tract, which, in turn, forms a triangle. At the level of this triangle and tract, in the olfactory tubercle, the nerve ends.

The ganglion cells of the retina give rise to the optic nerve. Entering the cranial cavity, it forms a cross and in the further passage begins to be called the "optic tract", which ends in the lateral geniculate body. It originates from central part optic pathway leading to the occipital lobe.

Auditory (aka vestibulocochlear) is made up of two. The cochlear root, formed from the cells of the spiral ganglion (belonging to the cochlear lamina), is responsible for the transmission of auditory impulses. The vestibular, coming from the vestibular ganglion, carries the impulses of the vestibular labyrinth. Both roots articulate into one in the internal auditory canal and go inward in the middle of the pons and medulla oblongata (the VII pair is somewhat lower). The fibers of the vestibule - a significant part of them - pass into the posterior longitudinal and vestibulospinal bundles, the cerebellum. Cochlear fibers stretch to the lower tubercles of the quadrigemina and the middle geniculate body. This is where the central auditory pathway ending in the temporal gyrus.

There is another sensory nerve that has received a zero number. At first, it was called "additional olfactory", but was later renamed terminal due to the location of the terminal plate nearby. Scientists have yet to reliably establish the functions of this pair.

Motor

The oculomotor, starting in the nuclei of the midbrain (below the aqueduct), appears on the brain base in the region of the pedicle. Before heading to the eye socket, it forms an extensive system. Its upper section is made up of two branches that go to the muscles - the upper straight line and the one that raises the eyelid. The lower part is represented by three branches, two of which innervate the rectus muscles - the median and lower, respectively, and the third goes to the inferior oblique muscle.

The nuclei lying in front of the aqueduct at the same level as the lower tubercles of the quadrupoloma, create the beginning of the trochlear nerve, which in the area of ​​​​the roof of the fourth ventricle appears on the surface, forms a decussation and stretches to the superior oblique muscle located in the orbit.

From the nuclei located in the tire of the bridge, fibers pass, forming the abducens nerve. It has an exit where the middle is located between the pyramid of the medulla oblongata and the bridge, after which it rushes into the orbit to the lateral rectus muscle.

Two components form the 11th, accessory, nerve. The upper one begins in the medulla oblongata - its cerebral nucleus, the lower one - in the dorsal (its upper part), and more specifically, the accessory nucleus, which is localized in the anterior horns. The roots of the lower part, passing through the foramen magnum, are directed into the cranial cavity and connected to the upper section of the nerve, creating a single trunk. It, leaving the skull, is divided into two branches. The fibers of the upper develop into the fibers of the 10th nerve, and the lower goes to the sternocleidomastoid and trapezius muscles.

Nucleus hypoglossal nerve is located in the rhomboid fossa (its lower zone), and the roots pass to the surface of the medulla oblongata in the middle of the olive and pyramid, after which they are combined into a single whole. The nerve emerges from the cranial cavity, then goes to the muscles of the tongue, where it produces 5 terminal branches.

Nerves with mixed fibers

The anatomy of this group is complex due to the branched structure, which allows innervating many departments and organs.

ternary

The area between the middle cerebellar peduncle and the pons is its exit point. The nucleus of the temporal bone forms the nerves: ophthalmic, maxillary and mandibular. They have sensory fibers, motor fibers are added to the latter. The orbital is located in the orbit (upper zone) and branches into the nasociliary, lacrimal and frontal. The maxillary has an exit to the surface of the face, after it penetrates through the infraorbital space.

The mandibular is divided into anterior (motor) and posterior (sensory) parts. They give the nervous network:

• the anterior is divided into chewing, deep temporal, lateral pterygoid and buccal nerves;
• posterior - into the median pterygoid, ear-temporal, inferior alveolar, mental and lingual, each of which is again divided into small branches (their number is 15 in total).

The mandibular division of the trigeminal nerve communicates with the auricular, submandibular, and hypoglossal nuclei.

The name of this nerve is known more than the other 11 pairs: many are familiar, at least by hearsay, about