The conductive path of the auditory analyzer and its neural composition. Vestibulocochlear organ - ear - hearing organ - organum vestibulocochleare

The auditory pathways begin in the cochlea in the neurons of the spiral ganglion (the first neuron). The dendrites of these neurons innervate the organ of Corti, the axons terminate in two nuclei of the bridge - the anterior (ventral) and posterior (dorsal) cochlear nuclei. From the ventral nucleus, impulses arrive to the following nuclei ( olives) of the self and the other side, whose neurons thus receive signals from both ears. It is here that the acoustic signals coming from both sides of the body are compared. From the dorsal nuclei, impulses enter through the inferior colliculi of the quadrigemina and the medial geniculate body into the primary auditory cortex - the posterior section of the superior temporal gyrus.

Schematic of auditory analyzer pathways

1 - snail;

2 - spiral ganglion;

3 - anterior (ventral) cochlear nucleus;

4 - posterior (dorsal) cochlear nucleus;

5 - the core of the trapezoid body;

6 - top olive;

7 - core of the lateral loop;

8 - nuclei of the posterior hillocks;

9 - medial cranked bodies;

10 - projection auditory zone.

Excitation of peripheral auditory neurons, subcortical and cortical primary cells occurs upon presentation of auditory stimuli of varying complexity. The farther away from the cochlea along the auditory tract, the more complex sound characteristics are required to activate neurons. The primary neurons of the spiral ganglion can be excited by pure tones, while already in the nuclei of the cochlea, a single-frequency sound can cause inhibition. To excite neurons, sounds of different frequencies are required.

In the lower colliculi of the quadrigemina there are cells that respond to frequency-modulated tones with a specific direction. In the auditory cortex there are neurons that respond only to the beginning of a sound stimulus, others only to its end. Some neurons fire on sounds of a certain duration, others on repeated sounds. The information contained in the sound stimulus is repeatedly recoded as it passes through all levels of the auditory tract. Due to the complex processes of interpretation, auditory pattern recognition occurs, which is very important for understanding speech.

The mammalian ear as an organ of balance

In vertebrates, the organs of balance are located in the membranous labyrinth, which develops from the anterior end of the lateral line system of fish. They consist of two chambers - a round sac (sacculus) and an oval sac (uterus, utriculus) - and three semicircular canals, which lie in three mutually perpendicular planes, in the cavities of the same-named bone canals. One of the legs of each duct, expanding, forms membranous ampullae. The portions of the wall of the sacs lined with sensory receptor cells are called spots, similar sections of the ampullae of the semicircular canals - scallops.

The epithelium of the spots contains receptor hair cells, on the upper surfaces of which there are 60–80 hairs (microvilli) facing the labyrinth cavity. In addition to hairs, each cell is equipped with one cilium. The cell surface is covered with a gelatinous membrane containing statoliths - calcium carbonate crystals. The membrane is supported by the static hairs of the hair cells. Receptor cells of spots perceive changes in gravity, rectilinear movements and linear accelerations.

The scallops of the ampullae of the semicircular canals are lined with similar hair cells and covered with a gelatinous dome - cupula into which cilia penetrate. They perceive the change in angular acceleration. The three semicircular canals are excellent for signaling head movements in three dimensions.

With a change in gravity, the position of the head, body, with acceleration of movement, etc., the membranes of the spots and the cupulas of the scallops are displaced. This leads to tension of the hairs, which causes a change in the activity of various enzymes of the hair cells and excitation of the membrane. Excitation is transmitted to the nerve endings, which branch out and surround the receptor cells like bowls, forming synapses with their bodies. Ultimately, the excitation is transmitted to the nuclei of the cerebellum, the spinal cord and the cortex of the parietal and temporal lobes of the cerebral hemispheres, where the cortical center of the balance analyzer is located.

body first neurons(Fig. 10) are located in the spiral node of the cochlea, ganglion spiral cochlearis, which is located in the spiral channel of the cochlea, canalis spiralis modioli. Dendrites of neurons approach receptors - the hair cells of the organ of Corti, and axons form pars cochlearis n. vestibulocochlearis, in which they reach the ventral and dorsal cochlear nuclei in the region of the lateral angles of the rhomboid fossa. Bodies are located in these nuclei second neurons.

Most axons second neurons of the ventral nucleus passes to the opposite side of the bridge, forming a trapezoid body, corpus trapezoideum. The trapezoid body has an anterior and posterior nuclei, in which the bodies are located third neurons. Their axons form a lateral loop, lemniscus lateralis, the fibers of which, within the isthmus of the rhomboid brain, approach two subcortical centers of hearing:

1) lower mounds of the roof of the midbrain, colliculi inferiors tecti mesencephali;

2) medial geniculate bodies, corpora geniculata mediales.

axons second neurons of the dorsal nucleus also pass to the opposite side, forming brain strips, striae medullares, and enter into the composition of the lateral loop. Part of the fibers of this loop are switched to third neurons in the nuclei of the lateral loop within the triangle of the loop. The axons of these neurons reach the above subcortical centers of hearing.

The axons of the last fourth neurons within the medial geniculate bodies pass through the posterior part of the posterior pedicle of the internal capsule, form auditory radiation and reach the cortical nucleus of the auditory analyzer within the middle part of the superior temporal gyrus, gyrus temporalis superior(gyrus of Heschl).

The axons of the fourth neurons of the inferior colliculus of the midbrain roof are the initial structures of the extrapyramidal tegmental-spinal tract, tractus tectospinalis, in which NI reach the motor neurons of the anterior columns of the spinal cord.

Some of the axons of the second neurons of the ventral and dorsal nuclei do not pass to the opposite side of the rhomboid fossa, but go along their side as part of the lateral loop.

Function. The auditory analyzer provides the perception of environmental fluctuations in the range from 16 to 2400 Hz. It determines the source of the sound, its strength, distance, propagation speed, provides stereognosic perception of sounds.

Rice. 10. Pathways of the auditory analyzer. 1 - thalamus; 2 - trigonum lemnisci; 3 - lemniscus lateralis; 4 - nucleus cochlearis dorsalis; 5 - cochlea; 6 - pars cochlearis n. vestibulocochlearis; 7, organum spirale; (8) ganglion spirale cochleae; 9 - tractus tectospinalis; 10 - nucleus cochlearis ventralis; 11 - corpus trapezoideum; 12 - striae medullares; 13 - colliculi inferiores; 14 - corpus geniculatum mediale; 15, radiatio acustica; 16 - gyrus temporalis superior.

The conductive path of the auditory analyzer ensures the conduction of nerve impulses from special auditory hair cells of the spiral (Corti) organ to the cortical centers of the cerebral hemispheres (Fig. 2)

The first neurons of this pathway are represented by pseudo-unipolar neurons, whose bodies are located in the spiral node of the cochlea of ​​the inner ear (spiral canal). Their peripheral processes (dendrites) end on the outer hair sensory cells of the spiral organ

Spiral organ, first described in 1851. Italian anatomist and histologist A Corti * is represented by several rows of epithelial cells (supporting cells of the outer and inner pillar cells) among which are placed the inner and outer hair sensory cells that make up the receptors of the auditory analyzer.

* Court Alfonso (Corti Alfonso 1822-1876) Italian anatomist. Born in Camba-ren (Sardinia) Worked as a dissector for I. Girtl, later as a histologist in Würzburg. Ut-rechte and Turin. In 1951 first described the structure of the spiral organ of the cochlea. He is also known for his work on the microscopic anatomy of the retina. comparative anatomy of the auditory apparatus.

The bodies of sensory cells are fixed on the basilar plate. The basilar plate consists of 24,000 racing transversely arranged collagen fibers (strings), the length of which gradually increases from the base of the cochlea to its apex from 100 µm to 500 µm with a diameter of 1–2 µm.

According to the latest data, collagen fibers form an elastic network located in a homogeneous ground substance, which resonates to sounds of different frequencies as a whole with strictly graduated vibrations. "tuned" to resonance at a given wave frequency

The human ear perceives sound waves with an oscillation frequency of 161 Hz to 20,000 Hz. For human speech, the most optimal limits are from 1000 Hz to 4000 Hz.

When certain sections of the basilar plate vibrate, tension and compression of the hairs of sensory cells corresponding to this section of the basilar plate occurs.

Under the action of mechanical energy in hair sensory cells, which change their position by only the size of the diameter of an atom, certain cytochemical processes occur, as a result of which the energy of external stimulation is transformed into a nerve impulse. Conduction of nerve impulses from special auditory hair cells of the spiral (Corti) organ to the cortical centers of the cerebral hemispheres is carried out using the auditory pathway.

The central processes (axons) of the pseudounipolar cells of the cochlear spiral ganglion leave the inner ear through the internal auditory meatus, gathering into a bundle, which is the cochlear root of the vestibulocochlear nerve. The cochlear nerve enters the substance of the brain stem in the region of the cerebellopontine angle, its fibers end on the cells of the anterior (ventral) and posterior (dorsal) cochlear nuclei, where the bodies of II neurons are located.

The axons of the cells of the posterior cochlear nucleus (II neurons) emerge on the surface of the rhomboid fossa, then go to the median sulcus in the form of brain strips, crossing the rhomboid fossa across the border of the pons and medulla oblongata. In the region of the median sulcus, the bulk of the fibers of the brain strips are immersed in the substance of the brain and pass to the opposite side, where they follow between the anterior (ventral) and posterior (dorsal) parts of the bridge as part of the trapezoid body, and then, as part of the lateral loop, go to the subcortical centers of hearing. part of the fibers of the brain strip joins the lateral loop of the side of the same name.

The axons of the cells of the anterior cochlear nucleus (II neurons) end on the cells of the anterior nucleus of the trapezoid body of their side (smaller part) or in the depth of the bridge to the similar nucleus of the opposite side, forming a trapezoid body.

A set of axons of III neurons, whose bodies lie in the region of the posterior nucleus of the trapezoid body, constitute the lateral loop. The dense bundle of the lateral loop formed at the lateral edge of the trapezoid body abruptly changes direction to ascending, following further near the lateral surface of the brain stem in its tire, deviating more and more outward, so that in the region of the isthmus of the rhomboid brain, the fibers of the lateral loop lie superficially, forming a triangle of the loop .

In addition to fibers, the lateral loop includes nerve cells that make up the nucleus of the lateral loop. In this nucleus, part of the fibers emanating from the cochlear nuclei and nuclei of the trapezoid body is interrupted.

The fibers of the lateral loop end in the subcortical auditory centers (medial geniculate bodies, lower hillocks of the midbrain roof plate), where IV neurons are located.

In the lower hillocks of the roof plate, the midbrain forms the second part of the tectospinal tract, the fibers of which, passing in the anterior roots of the spinal cord, end segmentally on the motor animal cells of its anterior horns. Through the described part of the occlusal-spinal tract, involuntary protective motor reactions to sudden auditory stimuli are carried out.

The axons of the cells of the medial geniculate bodies (IV neurons) pass in the form of a compact bundle through the posterior part of the posterior leg of the internal capsule, and why, scattering like a fan, form auditory radiation and reach the cortical nucleus of the auditory analyzer, in particular, the superior temporal gyrus (Geschl's gyrus *).

* Heschl Richard (Heschl Richard. 1824 - 1881) - Austrian anatomist and ptologist. was born in Welledorf (Styria). He received his medical education in Vienna. Professor of anatomy in Olomouc, pathology in Krakow, clinical medicine in Graz. Studied general problems of pathology. In 1855 he published a manual on general and special pathological human anatomy

The cortical nucleus of the auditory analyzer perceives auditory stimuli mainly from the opposite side. Due to incomplete decussation of the auditory pathways, unilateral lesion of the lateral loop. subcortical auditory center or cortical nucleus of the Jurassic auditory analysis may not be accompanied by a sharp hearing disorder, only a decrease in hearing in both ears is noted.

With neuritis (inflammation) of the vestibulocochlear nerve, hearing loss is often observed.

Hearing loss can occur as a result of selective irreversible damage to the hair sensory cells when large doses of antibiotics with ototoxic effects are introduced into the body.

The conducting path of the vestibular (statokinetic) analyzer

The conductive path of the vestibular (statokinetic) analyzer ensures the conduction of nerve impulses from the hair sensory cells of the ampullae scallops (ampullae of the semicircular ducts) and spots (elliptical and spherical sacs) to the cortical centers of the cerebral hemispheres (Fig. 3).

The bodies of the first neurons of the statokinetic analyzer lie in the vestibule node, located at the bottom of the internal auditory meatus. The peripheral processes of the pseudounipolar cells of the vestibular ganglion terminate on the hairy sensory cells of the ampullar ridges and spots.

The central processes of pseudounipolar cells in the form of the vestibular part of the vestibulocochlear nerve, together with the cochlear part, enter the cranial cavity through the internal auditory opening, and then into the brain to the vestibular nuclei lying in the vestibular field, area vesribularis of the rhomboid fossa

The ascending part of the fibers ends on the cells of the superior vestibular nucleus (Bekhterev *) The fibers that make up the descending part end in the medial (Schwalbe **), lateral (Deiters ***) and lower Roller ****) vestibular nuclei pax

* Bekhterev V M (1857-1927) Russian neuropathologist and psychiatrist. Graduated from the St. Petersburg Medical and Surgical Academy in 1878 Since 1894 he headed the Department of Neuropathology and Psychiatry of the Military Medical Academy In 1918 he founded the institute for the study of the brain and mental activity

** Gustav Schwalbe (Schwalbe Gustav Albert 1844-1916) - German anatomist and anthropologist. Born in Caedlingburg. He studied medicine in Berlin, Zurich and Bonn. He was engaged in histology and physiology of muscles, morphology of the lymphatic and nervous systems, sensory organs. Author of "Textbook of Neurology" (1881)

*** Deiters Otto (Deiters Otto Friedrich Karl 1844-1863) - German anatomist and histologist. Born in Bonn. He received his medical education in Berlin. He worked as a doctor in Bonn, and then was elected professor of anatomy and histology at Bonn University. He studied the subtle structure of the brain. organ of hearing and balance, comparative anatomy of the central nervous system. first described the reticulum of the brain and proposed the term "network reticular formation"

**** Roller H.F. (Roller Ch.F.W.) - German psychiatrist

The axons of the cells of the vestibular nuclei (II neurons) form a series of bundles that go to the cerebellum, to the nuclei of the nerves of the eye muscles, the nuclei of the autonomic centers, the cerebral cortex, to the spinal cord

Part of the axons of the cells of the lateral and superior vestibular nucleus in the form of a pre-door-spinal path is directed to the spinal cord, located along the periphery at the border of the anterior and lateral cords and ends segmentally on the motor animal cells of the anterior horns, carrying out vestibular impulses to the muscles of the neck of the trunk and extremities, providing maintenance body balance

Part of the axons of neurons of the lateral vestibular nucleus is directed to the medial longitudinal bundle of its and the opposite side, providing a connection of the balance organ through the lateral nucleus with the nuclei of the cranial nerves (III, IV, VI nar), innervating the muscles of the eyeball, which allows you to maintain the direction of gaze, despite changes in position heads. Maintaining the balance of the body is largely dependent on the coordinated movements of the eyeballs and head.

The axons of the cells of the vestibular nuclei form connections with the neurons of the reticular formation of the brain stem and with the nuclei of the tegmentum of the midbrain

The appearance of vegetative reactions (decreased heart rate, drop in blood pressure, nausea, vomiting, blanching of the face, increased peristalsis of the gastrointestinal tract, etc.) in response to excessive irritation of the vestibular apparatus can be explained by the presence of connections between the vestibular nuclei through the reticular formation with the nuclei of the vagus and glossopharyngeal nerves

Conscious determination of the position of the head is achieved by the presence of connections between the vestibular nuclei and the cerebral cortex. At the same time, the axons of the cells of the vestibular nuclei pass to the opposite side and are sent as part of the medial loop to the lateral nucleus of the thalamus, where they switch to III neurons

Axons of III neurons pass through the posterior part of the posterior leg of the internal capsule and reach the cortical nucleus of the statokinetic analyzer, which is scattered in the cortex of the superior temporal and postcentral gyri, as well as in the superior parietal lobe of the cerebral hemispheres

Damage to the vestibular nuclei. nerve and labyrinth is accompanied by the appearance of the main symptoms of dizziness, nystagmus (rhythmic twitching of the eyeballs), disorders of balance and coordination of movements

The conductive path of the auditory analyzer connects the organ of Corti with the overlying parts of the central nervous system. The first neuron is located in the spiral node, located at the base of the hollow cochlear node, passes through the channels of the bone spiral plate to the spiral organ and ends at the outer hair cells. The axons of the spiral ganglion make up the auditory nerve, which enters the brainstem in the region of the cerebellopontine angle, where they end in synapses with the cells of the dorsal and ventral nuclei.

The axons of the second neurons from the cells of the dorsal nucleus form the brain strips located in the rhomboid fossa on the border of the bridge and the medulla oblongata. Most of the brain strip passes to the opposite side and, near the midline, passes into the substance of the brain, connecting to the lateral loop of its side. The axons of the second neurons from the cells of the ventral nucleus are involved in the formation of the trapezoid body. Most of the axons pass to the opposite side, switching in the superior olive and nuclei of the trapezoid body. A smaller part of the fibers ends on its side.

The axons of the nuclei of the superior olive and trapezoid body (III neuron) are involved in the formation of the lateral loop, which has fibers of II and III neurons. Part of the fibers of the II neuron are interrupted in the nucleus of the lateral loop or switched to the III neuron in the medial geniculate body. These fibers of the III neuron of the lateral loop, passing by the medial geniculate body, end in the lower colliculus of the midbrain, where tr.tectospinalis is formed. Those fibers of the lateral loop related to the neurons of the superior olive, from the bridge penetrate into the upper legs of the cerebellum and then reach its nuclei, and the other part of the axons of the superior olive goes to the motor neurons of the spinal cord. The axons of the III neuron, located in the medial geniculate body, form the auditory radiance, ending in the transverse Heschl gyrus of the temporal lobe.

The central representation of the auditory analyzer.

In humans, the cortical auditory center is the transverse gyrus of Heschl, including, in accordance with Brodmann's cytoarchitectonic division, fields 22, 41, 42, 44, 52 of the cerebral cortex.

In conclusion, it should be said that, as in other cortical representations of other analyzers in the auditory system, there is a relationship between the zones of the auditory cortex. Thus, each of the zones of the auditory cortex is connected with other zones organized tonotopically. In addition, there is a homotopic organization of connections between similar zones of the auditory cortex of the two hemispheres (there are both intracortical and interhemispheric connections). At the same time, the main part of the bonds (94%) homotopically terminate on the cells of layers III and IV, and only a small part - in layers V and VI.

Vestibular peripheral analyzer. On the eve of the labyrinth there are two membranous sacs with the otolith apparatus in them. On the inner surface of the sacs there are elevations (spots) lined with neuroepithelium, consisting of supporting and hair cells. The hairs of sensitive cells form a network, which is covered with a jelly-like substance containing microscopic crystals - otoliths. With rectilinear movements of the body, otoliths are displaced and mechanical pressure occurs, which causes irritation of neuroepithelial cells. The impulse is transmitted to the vestibular node, and then along the vestibular nerve (VIII pair) to the medulla oblongata.

On the inner surface of the ampullae of the membranous ducts there is a protrusion - an ampullar comb, consisting of sensitive neuroepithelial cells and supporting cells. Sensitive hairs sticking together are presented in the form of a brush (cupula). Irritation of the neuroepithelium occurs as a result of the movement of the endolymph when the body is displaced at an angle (angular accelerations). The impulse is transmitted by the fibers of the vestibular branch of the vestibulocochlear nerve, which ends in the nuclei of the medulla oblongata. This vestibular zone is connected with the cerebellum, spinal cord, nuclei of the oculomotor centers, and the cerebral cortex. In accordance with the associative links of the vestibular analyzer, vestibular reactions are distinguished: vestibulosensory, vestibulovegetative, vestibulosomatic (animal), vestibulocerebellar, vestibulospinal, vestibulo-oculomotor.

The conducting path of the vestibular (statokinetic) analyzer provides the conduction of nerve impulses from the hair sensory cells of the ampullar scallops (ampulla of the semicircular ducts) and spots (elliptical and spherical sacs) to the cortical centers of the cerebral hemispheres.

The bodies of the first neurons of the statokinetic analyzer lie in the vestibular node, located at the bottom of the internal auditory canal. The peripheral processes of the pseudounipolar cells of the vestibular ganglion terminate on the hairy sensory cells of the ampullar ridges and spots.

The central processes of pseudounipolar cells in the form of the vestibular part of the vestibulocochlear nerve, together with the cochlear part, enter the cranial cavity through the internal auditory opening, and then into the brain to the vestibular nuclei lying in the vestibular field, area vesribularis of the rhomboid fossa.

The ascending part of the fibers ends on the cells of the superior vestibular nucleus (Bekhterev *) The fibers that make up the descending part end in the medial (Schwalbe **), lateral (Deiters ***) and lower Roller ****) vestibular nuclei pax

Axons of cells of the vestibular nuclei (II neurons) form a series of bundles that go to the cerebellum, to the nuclei of the nerves of the eye muscles, the nuclei of the autonomic centers, the cerebral cortex, to the spinal cord

Part of cell axons lateral and superior vestibular nucleus in the form of a vestibulo-spinal tract, it is directed to the spinal cord, located along the periphery at the border of the anterior and lateral cords and ends segmentally on the motor animal cells of the anterior horns, carrying out vestibular impulses to the muscles of the neck of the trunk and extremities, ensuring the maintenance of body balance

Part of axons of neurons lateral vestibular nucleuspa is directed to the medial longitudinal bundle of its and the opposite side, providing a connection of the balance organ through the lateral nucleus with the nuclei of the cranial nerves (III, IV, VI nar), innervating the muscles of the eyeball, which allows you to maintain the direction of gaze, despite changes in the position of the head. Maintaining the balance of the body is largely dependent on the coordinated movements of the eyeballs and head.

Axons of cells of the vestibular nuclei form connections with neurons of the reticular formation of the brain stem and with the nuclei of the tegmentum of the midbrain

The appearance of vegetative reactions(slowing of the pulse, drop in blood pressure, nausea, vomiting, blanching of the face, increased peristalsis of the gastrointestinal tract, etc.) in response to excessive irritation of the vestibular apparatus can be explained by the presence of connections between the vestibular nuclei through the reticular formation with the nuclei of the vagus and glossopharyngeal nerves

Conscious determination of the position of the head is achieved by the presence of connections vestibular nuclei with the cerebral cortex At the same time, the axons of the cells of the vestibular nuclei pass to the opposite side and are sent as part of the medial loop to the lateral nucleus of the thalamus, where they switch to III neurons

Axons of III neurons pass through the back of the posterior leg of the internal capsule and reach cortical nucleus stato-kinetic analyzer, which is scattered in the cortex of the superior temporal and postcentral gyri, as well as in the superior parietal lobe of the cerebral hemispheres

Foreign bodies in the external auditory canal most often found in children when, during the game, they push various small objects into their ears (buttons, balls, pebbles, peas, beans, paper, etc.). However, in adults, foreign bodies are often found in the external auditory canal. They can be fragments of matches, pieces of cotton wool that get stuck in the ear canal at the time of cleaning the ear from sulfur, water, insects, etc.

CLINICAL PICTURE

Depends on the size and nature of foreign bodies of the outer ear. So, foreign bodies with a smooth surface usually do not injure the skin of the external auditory canal and may not cause discomfort for a long time. All other items quite often lead to reactive inflammation of the skin of the external auditory canal with the formation of a wound or ulcerative surface. Foreign bodies swollen from moisture, covered with earwax (cotton wool, peas, beans, etc.) can lead to blockage of the ear canal. It should be borne in mind that one of the symptoms of a foreign body in the ear is hearing loss as a violation of sound conduction. It occurs as a result of a complete blockage of the ear canal. A number of foreign bodies (peas, seeds) are capable of swelling under conditions of humidity and heat, so they are removed after the infusion of substances that contribute to their wrinkling. Insects caught in the ear, at the time of movement, cause unpleasant, sometimes painful sensations.

Diagnostics. Recognition of foreign bodies is usually not difficult. Large foreign bodies linger in the cartilaginous part of the ear canal, and small ones can penetrate deep into the bone section. They are clearly visible with otoscopy. Thus, the diagnosis of a foreign body in the external auditory canal should and can be made by otoscopy. In cases where, with unsuccessful or inept attempts to remove a foreign body made earlier, inflammation has occurred with infiltration of the walls of the external auditory canal, diagnosis becomes difficult. In such cases, if a foreign body is suspected, short-term anesthesia is indicated, during which both otoscopy and removal of the foreign body are possible. X-rays are used to detect metallic foreign bodies.

Treatment. After determining the size, shape and nature of the foreign body, the presence or absence of any complication, a method for its removal is chosen. The safest method for removing uncomplicated foreign bodies is to wash them out with warm water from a Janet-type syringe with a capacity of 100-150 ml, which is carried out in the same way as removing the sulfur plug.

When you try to remove it with tweezers or forceps, a foreign body can slip out and penetrate from the cartilaginous section into the bony section of the ear canal, and sometimes even through the tympanic membrane into the middle ear. In these cases, the extraction of a foreign body becomes more difficult and requires great care and good fixation of the patient's head, short-term anesthesia is necessary. The hook of the probe must be passed behind the foreign body under visual control and pulled out. A complication of instrumental removal of a foreign body can be a rupture of the eardrum, dislocation of the auditory ossicles, etc. Swollen foreign bodies (peas, beans, beans, etc.) must be dehydrated beforehand by infusing 70% alcohol into the ear canal for 2-3 days, as a result of which they shrink and are removed without much difficulty by washing. Insects in contact with the ear are killed by infusing a few drops of pure alcohol or heated liquid oil into the ear canal, and then removed by rinsing.

In cases where a foreign body has wedged into the bone section and caused a sharp inflammation of the tissues of the ear canal or led to an injury to the eardrum, they resort to surgical intervention under anesthesia. An incision is made in the soft tissues behind the auricle, the posterior wall of the skin auditory canal is exposed and cut, and the foreign body is removed. Sometimes it is necessary to surgically expand the lumen of the bone section by removing part of its posterior wall.

The conduction path of the auditory analyzer

The conduction path of the auditory analyzer provides the conduction of nerve impulses from special auditory hair cells of the spiral (Corti) organ to the cortical centers of the cerebral hemispheres.

First neurons this path is represented by pseudo-unipolar neurons, the bodies of which are located in the spiral node of the cochlea of ​​the inner ear (spiral canal). Their peripheral processes (dendrites) end on the outer hairy sensory cells of the spiral organ.

Spiral organ, first described in 1851. Italian anatomist and histologist A Corti is represented by several rows of epithelial cells (supporting cells of the outer and inner pillar cells), among which are placed the inner and outer hair sensory cells that make up auditory analyzer receptors.

*Court Alfonso (Corti Alfonso 1822-1876) Italian anatomist. Born in Camba-ren (Sardinia) Worked as a dissector for I. Girtle, later as a histologist in Würzburg, Utrecht and Turin. In 1951, he first described the structure of the spiral organ of the cochlea. He is also known for his work on the microscopic anatomy of the retina. comparative anatomy of the auditory apparatus.

Sensory cell bodies are fixed on the basilar plate. The basilar plate consists of 24,000 thin transversely arranged collagen fibers (strings) the length of which from the base of the cochlea to its top gradually increases from 100 microns to 500 microns with a diameter of 1-2 microns

According to recent data, collagen fibers form an elastic network located in a homogeneous ground substance, which resonates to sounds of different frequencies as a whole with strictly graduated vibrations. Oscillatory movements from the perilymph of the scala tympani are transmitted to the basilar plate, causing the maximum oscillation of those parts of it that are "tuned" to resonance at a given wave frequency. For low sounds, such areas are located at the top of the cochlea, and for high sounds, at its base.

The human ear perceives sound waves with an oscillation frequency of 161 Hz to 20,000 Hz. For human speech, the most optimal limits are from 1000 Hz to 4000 Hz.

When certain sections of the basilar plate vibrate, tension and compression of the hairs of sensory cells corresponding to this section of the basilar plate occurs.

Under the action of mechanical energy in hair sensory cells, which change their position by only the size of the diameter of an atom, certain cytochemical processes occur, as a result of which the energy of external stimulation is transformed into a nerve impulse. Conduction of nerve impulses from special auditory hair cells of the spiral (Corti) organ to the cortical centers of the cerebral hemispheres is carried out using the auditory pathway.

central processes (axons)) pseudo-unipolar cells of the spiral node of the cochlea leave the inner ear through the internal auditory meatus, gathering in a bundle, which is the cochlear root of the vestibulocochlear nerve. The cochlear nerve enters the substance of the brain stem in the region of the cerebellopontine angle, its fibers end on the cells of the anterior (ventral) and posterior (dorsal) cochlear nuclei, where bodies of II neurons are located.

Training video of the auditory analyzer pathways