12 pairs of cranial nerves in Latin. Twelfth nerve - n. hypoglossus. Nerves with mixed fibers

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 condition of the nerves postnatal period 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 starts at nerve cells nasal mucous membranes, 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. From it originates the central part visual pathway going 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 (located somewhat lower VII couple). 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 large occipital foramen, 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. Nucleus temporal bone forms 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

The cranial nerves, also called the cranial nerves, form from the brain. There are 12 pairs with different functions. Different pairs can contain both afferent and efferent fibers, due to which the cranial nerves serve both to transmit and receive impulses.

The nerve can form motor, sensitive (sensory) or mixed fibers. The place of exit of different pairs is also different. The structure determines their function.

The olfactory, auditory and optic cranial nerves are formed by sensory fibers. They are responsible for the perception of relevant information, and the auditory are inextricably linked with the vestibular apparatus, and help to ensure orientation in space and balance.

Motor are responsible for the functions eyeball and language. They are formed by autonomic, sympathetic and parasympathetic fibers, which ensures the functioning of a certain part of the body or organ.

Mixed types of cranial nerves are formed simultaneously by sensory and motor fibers, which determines their function.

Sensitive FMN

How many brain nerves does a person have? From the brain, 12 pairs of cranial nerves (CNN) depart, which are able to innervate to various parts of the body.

The sensory function is performed by the following cranial nerves:

• olfactory (1 pair);
• visual (2 pairs);
• auditory (8 pairs).

The first pair passes through the nasal mucosa up to the olfactory center of the brain. This pair provides the ability to smell. With the help of medial bundles forebrain and 1 pair of FMN, a person has an emotional-associative reaction in response to any smells.

Pair 2 originates in ganglion cells located in the retina. Retinal cells react to a visual stimulus and transmit it to the brain for analysis using the second pair of FMNs.

The auditory or vestibulocochlear nerve is the eighth pair of cranial nerves and acts as a transmitter of auditory irritation to the corresponding analytical center. This pair is also responsible for the transmission of impulses from vestibular apparatus, which ensures the functioning of the equilibrium system. Thus, this pair consists of two roots - vestibular (balance) and cochlear (hearing).

Motor FMN

Motor function is carried out by the following nerves:

• oculomotor (3 pairs);
• block (4 pairs);
• outlet (6 pairs);
• facial (7 pairs);
• additional (11 pairs);
• sublingual (12 pair).

3 pair of FMN performs the motor function of the eyeball, provides pupil motility and eyelid movement. It can also be attributed to mixed type, since the motor activity of the pupil is carried out in response to sensitive stimulation by light.

4 pair of cranial nerves performs only one function - this is the movement of the eyeball down and forward, it is only responsible for the function of the oblique muscle of the eye.

The 6th pair also provides the movement of the eyeball, more precisely, only one function - its abduction. Thanks to the 3,4 and 6 pairs, a full circular movement of the eyeball is carried out. 6 pair also provides the ability to look away.

The 7th pair of cranial nerves is responsible for the mimic activity of the muscles of the face. The nuclei of the cranial nerves of the 7th pair are located behind the nucleus. It has a complex structure, due to which not only facial expressions are provided, but also salivation, lacrimation and taste sensitivity of the anterior part of the tongue are controlled.

The accessory nerve provides muscle activity to the neck and shoulder blades. Thanks to this pair of FMNs, head turns to the sides, raising and lowering the shoulder and bringing the shoulder blades together are carried out. This pair has two nuclei at once - cerebral and spinal, which explains the complex structure.

The last, 12th pair of cranial nerves is responsible for the movement of the tongue.

Mixed FMN

The following pairs of FMNs belong to the mixed type:

• trigeminal (5 pairs);
• glossopharyngeal (9para);
• wandering (10 pairs).

Facial FMN (7 pairs) is equally often referred to as a motor (motor) and mixed type, so the description in the tables may sometimes differ.

5 pair - the trigeminal nerve - this is the largest cranial nerve. It is distinguished by a complex branched structure and is divided into three branches, each of which innervates a different part of the face. Upper branch provides sensitive and motor function the upper third of the face, including the eyes, the middle branch is responsible for the sensation and movement of the muscles of the cheekbones, cheeks, nose and upper jaw, and the lower branch provides motor and sensory function mandible and chin.

Security swallowing reflex, sensitivity of the throat and larynx, as well as the back of the tongue provides - 9 pairs of FMN. It also provides reflex activity and saliva secretion.

The vagus nerve or 10th pair performs several important functions at once:

• swallowing and motility of the larynx;
• contraction of the esophagus;
• parasympathetic control of the heart muscle;
• ensuring the sensitivity of the mucous membrane of the nose and throat.

Nerve whose innervation occurs in the head, neck, abdominal and thoracic The human body is one of the most complex, which determines the number of functions performed.

Pathologies of sensitive cranial nerves

Most often, the lesion is associated with trauma, infection or hypothermia. Olfactory nerve pathologies (the first pair of cranial nerves) are often diagnosed in older people. Symptoms of a malfunction of this branch are loss of smell or the development of olfactory hallucinations.

The most common pathology of the optic nerve is stagnant process, swelling, narrowing of the arteries or neuritis. Such pathologies entail a decrease in visual acuity, the appearance of so-called "blind" spots in the field of vision, and the photosensitivity of the eyes.

Damage to the auditory process can occur in a variety of ways. various reasons, however, often the inflammatory process is associated with infections of the upper respiratory tract and meningitis. The following symptoms are characteristic of the disease in this case:

• hearing loss up to complete deafness;
• nausea and general weakness;
• disorientation;
• dizziness;
• ear pain.

The symptoms of neuritis are often accompanied by symptoms of damage to the vestibular nucleus, which is manifested by dizziness, problems with balance and nausea.

Pathologies of motor cranial nerves

Any pathology of motor or motor cranial insufficiencies, for example, 6 pairs, makes it impossible to perform them main function. Thus, paralysis of the corresponding part of the body develops.

With the defeat of the oculomotor cranial insufficiency (3 pairs), the patient's eye always looks down and protrudes slightly. It is impossible to move the eyeball in this case. Pathology of the 3rd pair is accompanied by drying of the mucosa due to a violation of lacrimation.

When the accessory nerve is damaged, muscle weakness or paralysis occurs, as a result of which the patient cannot control the muscles of the neck, shoulder, and collarbone. This pathology is accompanied characteristic disorder posture and shoulder asymmetry. Often the cause of damage to this pair of cranial nerves are injuries and accidents.

Pathologies of the twelfth pair lead to speech defects due to impaired tongue mobility. Without timely treatment possible development of a central or peripheral paralysis language. This in turn causes difficulty in eating and speech disorders. A characteristic symptom of such a violation is the tongue, moving towards the damage.

Pathologies of mixed craniocerebral insufficiency

According to doctors and patients themselves, trigeminal neuralgia is one of the most painful diseases. Such a lesion is accompanied by acute pain, which can be relieved by conventional means almost impossible. Pathologies facial nerve are often bacterial or viral in nature. There are frequent cases of the development of the disease after hypothermia.

With inflammation or damage to the glossopharyngeal nerve, there is an acute paroxysmal pain that affects the tongue, larynx and shoots through the face up to the ear. Often, the pathology is accompanied by a violation of swallowing, sore throat and cough.

The tenth pair is responsible for the work of some internal organs. Often her defeat is manifested by a violation of work gastrointestinal tract and pain in the stomach. Such a disease can lead to impaired swallowing function and laryngeal edema, as well as development, which can cause an unfavorable outcome.

Things to remember

The human nervous system is a complex structure that ensures the vital activity of the whole organism. Damage to the CNS and PNS occurs in several ways - as a result of trauma, with the spread of a virus or infection with the bloodstream. Any pathology affecting the brain nerves can lead to a number of severe disorders. To prevent this from happening, it is important to be attentive to your own health and seek qualified medical help in a timely manner.

Treatment of any damage to craniocerebral insufficiency is carried out by a doctor after a detailed examination of the patient. Defeat, compression or inflammation of craniocerebral insufficiency should be treated only by a specialist, self-treatment and replacement of alternative drug therapy can lead to the development of negative consequences and seriously harm the patient's health.

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 independently build reflex arcs of various types of reflexes, as well as navigate the topography from 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. Hemisphere big brain, superior 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 couple – 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 external cranked bodies, pillows of the thalamus and the upper mounds of the midbrain, where the subcortical visual centers. 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 of the 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 trigeminal ganglion.

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 sinus 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 opening into the pterygopalatine fossa, where it gives off branches that go to the oral cavity, nasal cavity and orbit.

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 the innervation of the teeth, gums of the 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, the lining of the brain.

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

The inferior alveolar nerve enters the mandibular canal, innervates the teeth and gums of the lower jaw, then passes through the mental foramen, 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.

Second higher education "Psychology" in MBA format

subject:Anatomy and evolution nervous system person.
Manual "Anatomy of the central nervous system"

12 pairs of cranial (cranial) nerves symmetrically depart from the human brain. Both morphologically and functionally, these nerves are not homogeneous. The following nerves are distinguished:

1) olfactory (I);
2) visual (II);
3) oculomotor (III);
4) block (IV);
5) trigeminal (U);
6) outlet (VI);
7) front (VII);
8) vestibulocochlear (VIII);
9) glossopharyngeal (IX);
10) wandering (X);
11) additional (XI);
12) sublingual (XII).

Each of the listed nerves has its own anatomical areas of entry (for sensory nerves) and exit (for motor nerves). In addition, the autonomic fibers of the parasympathetic division of the central nervous system may also be part of the cranial nerves.

The bulbs of the olfactory nerve lie on the sides of the longitudinal fissure at the base of the brain. From the bulb comes the olfactory tract, which expands into the olfactory triangle. Behind the longitudinal target on the lower surface of the hemispheres is the optic chiasm (II). From the inside, the brain stem goes around the oculomotor nerve (III), and outside - the trochlear nerve (IV). At the border of the bridge with the middle legs of the cerebellum, the trigeminal nerve (V) emerges. On the border of the bridge and the medulla oblongata, the abducens nerve (VI), the facial nerve (VII), and the vestibulocochlear nerve (VIII) exit in succession from the central fissure. On the border between the olive and the lower cerebellar peduncle, there are roots of the tongues of the pharyngeal nerve (IX), the vagus nerve (X), and the accessory nerve (XI). Between the pyramid and the olive, the roots of the hypoglossal nerve (XII) emerge. According to the function of the nerve fibers included in the nerve, several groups of cranial nerves are distinguished (Fig. 12.1).

Rice. 12.1. Classification of cranial nerves by function

Many cranial nerves are interconnected by connecting branches, in which sensory, motor and autonomic fibers can pass.

The nuclei of most nerves are located along the brain stem and enter the spinal cord: they secrete motor, sensory, vegetative (autonomous) nuclei. The exceptions are the olfactory and optic nerve, which do not have nuclei and are outgrowths of the brain.

Let's take a closer look at each of the nerves.

I pair - olfactory nerves. They start from the mucous membrane of the olfactory region of the nasal cavity, pass through the cranial cavity and approach the olfactory bulb. As the name implies, this nerve sends information to the brain about chemical composition odorous molecules, which serves as the basis for the emergence of olfactory sensations.

II pair - optic nerve contains axons of retinal ganglion cells. Undoubtedly, vision is the most important channel for receiving information about the world around us.

III pair - oculomotor nerve. Innervates the muscle that lifts the upper eyelid, superior, inferior, medial rectus and inferior oblique muscle of the eyeball. oculomotor nerve contains parasympathetic fibers innervating the sphincter of the pupil and the ciliary muscle of the eye.

IV paratrochlear nerve innervates the superior oblique muscle of the eyeball. With the help of the III, IV and VI pairs of nerves, the gaze is focused on the object.

V pair - trigeminal nerve is the main sensory nerve of the head. Trigeminal nerve innervates the skin of the face, eyeball and conjunctiva, hard meninges, the mucous membrane of the nose and mouth, most of the tongue, teeth and gums. Its motor fibers go to the chewing muscles and the muscles of the floor of the mouth. The most vivid (and at the same time the least pleasant) sensation associated with the trigeminal nerve is toothache, which almost everyone is familiar with.

VI pair - abducens nerve innervates the external rectus muscle of the eye.

VII pair - facial nerve. It is formed mainly by motor fibers, but it also includes parasympathetic fibers. The motor fibers of the facial nerve innervate all facial muscles. Human facial expressions play an important role in communication, helping to establish a more complete and mutual understanding on a non-verbal level.

VIII pair - vestibulocochlear nerve , which conducts irritation from the receptors of the inner ear. Hearing is the second (after vision) channel for information from the outside world.

IX pair - glossopharyngeal nerve . It conducts motor fibers to the constrictors of the pharynx and stylo-pharyngeal muscle, and sensory fibers - from the mucous membrane of the pharynx, tonsils, tympanic cavity, contains parasympathetic fibers.

X pair - vagus nerve , has the largest area of ​​innervation. It is the main parasympathetic nerve of the internal organs, and also conducts most afferent fibers from the organs in which it branches. With the help of this nerve, many psychosomatic and somatopsychic connections are organized.

XI pair - accessory nerve , has cranial and spinal roots, which are combined into a nerve trunk. Participates in the motor innervation of the pharynx and larynx, as well as the sternocleidomastoid and part of the trapezius muscle.

XII pair - hypoglossal nerve , is the motor nerve of the tongue. Human speech (his second signaling system, but to Pavlov) is largely provided by controlling the muscles of the larynx and tongue with the help of XI and XII pairs of nerves.

cranial nerves, n.n. craniales, These are nerves that are anatomically and functionally connected with the brain. There are 12 pairs of cranial nerves, which are indicated by Roman numerals (see Fig. 2, 5):

I pair - olfactory nerves, n.n. olfactorii;

II pair - optic nerve, n. opticus;

III pair - oculomotor nerve, n. oculomotorius;

IV pair - trochlear nerve, n. trochlearis;

V pair - trigeminal nerve, n. trigeminus;

VI pair - abducens nerve, n. abducens;

VII pair - facial nerve, n. facialis;

VIII pair - vestibulocochlear nerve, n. vestibulocochlearis;

IX pair - glossopharyngeal nerve, n. glossopharyngeus;

X pair - vagus nerve, n. vagus;

XI pair - accessory nerve, n. accessorius

XII pair - hypoglossal nerve, n. hypoglossus;

Rice. 9. Internal base of the skull with cranial nerves passing through it.

I and II pairs of cranial nerves in their development are associated with the forebrain, III-XII pairs - with various departments brain stem. At the same time, pairs III and IV are connected with the midbrain, V-VIII - with the bridge, and IX-XII - with the medulla oblongata.

According to the composition of the fibers, the cranial nerves are divided into 3 groups:

1) sensory nerves - I, II and VIII pairs;

2) motor nerves - IV, VI, XI and XII pairs;

3) mixed nerves - III, V, VII, IX and X pairs.

Sensory nerves are formed by centripetal fibers (central processes) of cells located in the nasal mucosa for pair I, in the retina for pair II, or in sensory ganglia for pair VIII.

The motor nerves are formed by the axons of the cells of the motor nuclei of the cranial nerves - IV, VI, XI and XII pairs.

Mixed nerves are different composition fibers. The sensory component present in the V, VII, IX and X pairs of cranial nerves is represented by the central processes of pseudo-unipolar cells located in the sensory nodes. The motor component present in III, IV, V, VI, VII, IX and X pairs of cranial nerves is represented by axons of the cells of the motor nuclei of the corresponding nerves. The parasympathetic component in the mixed nerves is found in III, VII, IX and X pairs of cranial nerves. It is formed by preganglionic parasympathetic fibers running from the parasympathetic nuclei of the corresponding nerves to the autonomic ganglia or by postganglionic fibers, which are the axons of the cells of these ganglia. The name, localization of the autonomic ganglia and nerves containing parasympathetic fibers are indicated in the table (see below).

It should be noted that the motor and mixed cranial nerves also contain sympathetic postganglionic fibers originating from the superior cervical ganglion of the sympathetic trunk.

Phylo- and ontogeny of the cranial nerves

In the process of phylogenesis, the cranial nerves lost their original segmental arrangement and became highly specialized. Olfactory and optic nerves - specific nerves of the sense organs, develop from the forebrain and are its outgrowths. They are formed by the processes of intercalary neurons, they are nerve formations that connect the organ of smell and the organ of vision with the brain.

The rest of the cranial nerves differentiated from the spinal nerves and are therefore fundamentally similar to them. Pair III (oculomotor nerve), IV pair (trochlear nerve) and V pair (abducens nerve) developed in connection with the cephalic anterior myotomes, which innervate the muscles of the eyeball formed in these myotomes. These nerves, as well as the XI and XII pairs, are similar in origin and function to the anterior roots of the spinal nerves.

V, VII, VIII, IX, X, pairs of cranial nerves are homologues of the posterior roots. These nerves are associated with muscles that develop from the muscles of the gill apparatus and developed from the lateral plates of the mesoderm, therefore they innervate the skin, the muscles of the corresponding visceral gill arches, and also contain visceral motor fibers that innervate the glands and organs of the head and neck.

A special place is occupied by the V pair (trigeminal nerve), which is formed by the fusion of two nerves - the deep ophthalmic, which innervates the skin of the front of the head, and the trigeminal nerve itself, which innervates the skin and muscles of the mandibular arch.

In the process of development, the VIII pair (vestibulocochlear nerve) separates from the facial nerve, which carries out specific innervation of the organ of hearing and balance. IX pair (glossopharyngeal nerve) and X pair (vagus nerve), consisting of visceral motor nerve fibers, develop by isolating the caudal part of the vagus nerve. hypoglossal nerve is complex in origin, as it is formed by the fusion of several spinal nerves, some of which move cranially and enter the region of the medulla oblongata.

Thus, all 12 pairs of cranial nerves can be divided into several groups by origin:

1. Nerves, derivatives of the brain - I ( n.n. olfactoria) and II pairs ( n.opticus).

2. Nerves developing in connection with the head myotomes - III ( n. oculomotorius), IV ( n. trochlearis), VI ( n. abducens) pairs.

3. Nerves derived from gill arches - V ( n. trigeminus), VII ( n.facialis), VIII ( n. vestibulo-cochlearis), IX ( n. glossopharyngeus),X( n. vagus), XI ( n. accessorius) pairs.

4. The nerve that developed by the fusion of the spinal nerves is the XII pair ( n. hypoglossus).

Cranial nerves, like spinal nerves, have nuclei (clusters of gray matter): somatic sensory (corresponding to the posterior horns of the gray matter of the spinal cord), somatic motor (corresponding to the anterior horns) and autonomic (corresponding to the lateral horns). Vegetative can be divided into visceral motor and visceral sensory, and visceral motor innervate not only unstriated (smooth) muscles, but also provide trophic skeletal muscles. Considering that the striated muscles have acquired the features of somatic muscles, all the nuclei of the cranial nerves related to such muscles, regardless of their origin, are better referred to as somatic motor nuclei.

As a result, the cranial nerves contain the same components as the spinal nerves.

Afferent components:

1) somatic sensory fibers coming from organs that perceive physical stimuli (pressure, pain, temperature, sound and light), i.e. skin, organs of hearing and vision - II, V, VIII.

2) visceral sensory fibers coming from organs that perceive internal stimuli, i.e. from nerve endings in the digestive organs and other viscera, from special organs of the pharynx, oral (organs of taste) and nasal (organ of smell) cavities - I, V, VII, IX, X.

Efferent Components:

1) somatic motor fibers innervating voluntary muscles, namely: muscles derived from the head myotomes, eye muscles (III, IV, VI), hyoid muscles (XII), as well as skeletal muscles secondarily displaced into the composition of the anterior digestive tract - the so-called muscles of the gill apparatus, which in mammals and humans have become chewing, mimic, etc. (V, VII, IX, X, XI);

2) visceral motor autonomic fibers (parasympathetic and sympathetic fibers) that innervate the visceral muscles, i.e. involuntary musculature of vessels and internal organs, the muscle of the heart, as well as various kinds of glands (secretory fibers), - V, VII, IX, X. Of the 12 pairs of cranial nerves, the VIII nerve is somatic sensitive, the somatic motor nerves are III, IV, VI, XI , XII. The rest of the nerves are mixed. The olfactory nerve, which can be called the visceral sensory, and the visual - somatic sensory - occupy a special position, being outgrowths of the brain.

Scheme for the study and description of cranial nerves

1. Numbering and name of the nerve (Russian, Latin).

2. Functional characteristics (motor, sensory, mixed).

3. Source of nerve development.

4. Nerve nuclei (name, functional characteristics, topography).

5. The principle of nerve formation, sensitive nodes of nerves.

6. Place of entry (sensory) or exit (motor, parasympathetic) nerves from the brain.

7. Place of entry or exit of nerves from the skull.

8. The course of the nerve on the periphery.

9. Parasympathetic nodes associated with nerves.

10. Main trunks and branches of the nerve, their area of ​​innervation.

Rice. 10. Areas of innervation of the cranial nerves (scheme).