INNER EAR

From Big Medical Encyclopedia

INNER EAR (auris interna) — system of channels of a temporal bone and the receptor device of acoustical and statokinetic analyzers which is in them. Complexity of a shape of an inner ear gave the grounds to call it also a labyrinth — labyrinthus.

At the lowest animals the body serving for preservation of balance is the static device (statocyst). At coelenterates it has an appearance of freely outstanding flask. Statocysts need to be considered complication of development the deepening in an ectoderm covered with an epithelium with hairs and containing stato-or an otolith (a mineral concrement). Further complication is transformation of a pole into the closed bubble with an otolith inside called «an acoustical bubble» which, however, has no relation to hearing and reacts, apparently, only to tactile stimulation. The ear labyrinth for the first time appears at vertebrate animals. Already fishes have well developed semicircular channels, sacks and in embryo a snail. The snail receives a characteristic form only at mammals, it consists of 1,5 — 5 curls.

The first rudiment of V. at. it is found in a human germ by the end of the first month in the form of emboly of an ectoderm in depth on both sides of and behind a metencephal. The pole is gradually formed, edges goes deep and, having plunged into a mesoderm, otshnurovyvatsya in the form of a bubble. In process of immersion of a bubble there is its differentiation on top and bottom departments. Webby semicircular channels, and from lower — a snail are formed of an upper part. In places where the internal vystilka of an acoustical bubble comes to close contact with fibers of an acoustical nerve, there is a formation of a multilayer cylindrical epithelium, from to-rogo then kutikulyarny little bodies of the receptor device of ampoules of semicircular channels, sacks and a snail form. The bone capsule B. at. it is formed by gradual ossification of a mesoderm around a webby labyrinth.

Anatomy

Fig. 2. Section of a snail: 1 — ganglion spirale cochleae; 2 — scala vestibuli; 3 — ductus cochlearis; 4 — scala tympani; 5 — pars cochlearis n. vestibulocochlearis; 6 — modiolus; 7 — organon spirale. Fig. 3. Cross-section of a round of a snail: 1 — membrana vestibularis; 2 — ductus cochlearis; 3 — membrana tectoria; 4 — stria vascularis; 5 — cellulae phalangae ext.; 6 — membrana basilaris with the spiral body located on it; 7 — cellula pilaris ext.; 8 — cellula pilaris int.; 9 — pars cochlearis n. vestibulocochlearis; 10 — scala tympani; 11 — lamina spiralis secundaria; 12 — ganglion spirale.
with Fig. 4. The right bone labyrinth (is opened) and the webby labyrinth consisting in it: 1 — saccus endolymphaticus; 2 — ductus endolymphaticus; 3 — ductus semicircularis post.; 4 — crus membranaceum commune; 5 — n. ampullaris post.; 6 — ductus reuniens; 7 — v. labyrinthi; 8 — n. saccularls; 9 — ductus cochlearis; 10 — a. labyrinthi; 11 — pars cochlearis n. vestibulocochlearis; 12 — pars vestibularis n. acustici; 13 — sacculus; 14 — ductus utriculosaccularis; 15 — utriculus; 16 — ductus semicircularis ant.; 17 — dyctus semicircularis lat.

Century at., or ear labyrinth (tsvetn. fig. 2 — 4), is in more thickly stony part (pars petrosa) of a temporal bone and consists of system of the bone channels which are reported with each other — a bone labyrinth (labyrinthus osseus), in Krom the webby labyrinth (labyrinthus membranaceus) is movably strengthened. Outlines of a bone labyrinth almost completely repeat outlines webby, being as if its capsule. The webby labyrinth represents a loop system of channels in which there are trailer devices of an eighth cranial nerve (n. vestibulocochlear is). The space between a bone and webby labyrinth called by perilymphangeal is filled with liquid — a perilympha (perilympha), the structure a cut is similar to composition of cerebrospinal liquid. The webby labyrinth is as if submersed in a perilympha, it is movably strengthened in the bone case by means of a row connective tissue by tyazhy and filled with liquid — an endolymph (endolympha), on structure a little different from a perilympha. The perilymphangeal space (spatium perilymphaticum) is connected with the subarachnoidal narrow bone channel called by a water supply system of a snail (aquaeductus cochleae, s. ductus perilymphaticus). The endolymphatic space of such message with a subarachnoid space has no. From endolymphatic space very narrow course — the water supply system of a threshold (aquaeductus vestibuli, s. ductus endolymphaticus) — conducts in the small closed tank — an endolymphatic sack (saccus endolymphaticus) put in the thickness of a firm meninx on a back surface of a pyramid.

The bone labyrinth consists of three departments: thresholds (vestibulum), semicircular channels (canales semicirculares ossei) and snail (cochlea).

The threshold forms the central part of a labyrinth. Kzadi and knaruzh it passes into semicircular canals, and kpered and knutr — in a snail. The internal wall of a cavity of a threshold is turned to a back cranial pole and makes a bottom of internal acoustical pass. Its surface is divided a small bone crest into two parts from which one — anteroinferior — is called spherical deepening (recessus sphaericus), and another — elliptic deepening (recessus ellipticus). In spherical deepening the webby spherical sack — sacculus, in elliptic — an elliptic sack — a utricle (utriculus) where semicircular channels fall the ends is located. In a mid-fellow of both deepenings groups of the small openings forming on a surface flat eminences in the form of trellised spots — maculae cribrosae are located. They are intended for branches of a vestibular part (pars vestibularis) of a nerve. The outside wall of a threshold is turned to a drum cavity and is engaged in a most part with a window of a threshold (fenestra vestibuli). Semicircular channels are located in three planes almost perpendicular each other. One of the ends of each channel is expanded and another is called an ampullar leg (crus osseum ampullare) — a simple leg (crus osseum simplex). On an arrangement in a bone distinguish: upper — frontal, or front (canalis semicircularis ant.), back — sagittal (canalis semicircularis post.) and lateral — horizontal (canalis semicircularis lat.) channels. Both ends of each semicircular channel conduct in a threshold, only two simple legs of back and upper channels connect among themselves, forming the general leg (crus osseum commune), and are reported with a threshold one general opening.

The bone snail represents gyrose the channel departing from a threshold; it bends around spiralno 2kh/2 time the horizontal axis and is gradually narrowed to a top. The central bone core carries the name modiolus. Around a core the narrow bone plate spiralno coils, to a cut it is strongly attached, making its direct continuation, the connective tissue membrane called by a basal membrane (membrana basilaris). Besides, the thin connective tissue membrane — a vestibular membrane (membrana vestibularis) called by also reyssnerovy membrane up departs from a bone spiral plate (lamina spiralis ossea) at an acute angle lateralno. The space which is formed between a basal and vestibular membrane is called a cochlear channel (ductus cochlearis), it is filled with an endolymph. Up and from top to bottom from it there are perilymphangeal spaces forming two floors. The first floor is called a drum ladder (scala tympani), upper — a ladder of a threshold (scala vestibuli). Ladders on a top of a snail connect with each other the opening of a snail called by helicotrema. The core of a snail is penetrated by longitudinal tubules (canales longitudinales modioli) for passing of nerve fibrils. On the periphery of a core its twisting canal (canalis spiralis cochleae) extends spiralno, in it nervous cells which form a spiral node of a snail — ganglion spirale cochleae are located. In a bone labyrinth from a skull conducts internal acoustical pass (meatus acusticus internus), to Krom there go preddverno-cochlear and facial nerves. The cranial opening of the channel is on a back surface of a pyramid, and internal comes to an end in a bone plate, edges is called a bottom of internal acoustical pass (fundus meatus acustici interni) and makes a part of a medial wall of a threshold and a snail.

The webby labyrinth consists of two sacks of a threshold, three semicircular channels, a channel of a snail, water supply systems of a threshold and a snail. All these departments of a webby labyrinth represent system of the educations which are reported with each other. The elliptic sack is in an upper part of a threshold, it is connected with a medial wall of a threshold the connective tissue bunches and fibers of the item utricularis passing through an upper trellised spot. According to it the inner surface of the lower wall of a sack has the eminence formed by a sensitive epithelium and carries the name of a spot of an elliptic sack (macula utriculi). In an elliptic sack conduct three ampullar and two simple legs of semicircular channels. Sacculus has the form of a convexo-plane lens and in the bottom passes into the canal (ductus reuniens) connecting it to a cochlear channel (ductus cochlearis). Sacculus and utriculus are reported among themselves by an endolymphatic channel (ductus endolymphaticus).

In a wall of a webby labyrinth of fiber of an eighth cranial nerve terminate in certain places. Three of them are located in ampoules and are called ampullar combs (cristae ampullares), two are in sacks and carry the name of spots (maculae sacculi et utriculi), the last is all trailer nervous device of a snail known under the name of spiral (kortiyev) body (organon spirale).

The webby snail represents spiralno gyrose a channel of triangular section.

Arteries inner ear come from a labyrinth artery (a. labyrinthi), edges departs from a basilar artery (a. basilaris). A venous blood of a labyrinth gathers in the texture lying in internal acoustical pass. From a threshold and semicircular channels a venous blood flows hl. obr. through the vein passing in a water supply system of a threshold in a cross sine of a firm meninx. Veins snails bring blood to the lower stony sine. The inner ear receives an innervation from the VIII pair of cranial nerves, each of which, having entered internal acoustical pass, breaks up to 3 branches: upper, average and lower. Upper and average branches form a nerve of a threshold — the item vestibularis, lower corresponds to a nerve of a snail — the item cochlearis (see the Eighth cranial nerve).

Histology

Gistol, the structure of a wall of a webby labyrinth is rather simple. The wall of vestibular department of a webby labyrinth is covered by a flat single-layer epithelium. This epithelium in the field of ampullar combs passes in cubic and cylindrical, located on a basal membrane, to a cut connecting fabric outside prilezhit. The network of the tense perilymphangeal crossing points consists of the connective tissue fibers getting on the one hand into the Endosteum covering walls of a bone labyrinth, and with another — in a connective tissue cover of webby walls. In .ety crossing points there pass blood vessels.

On the structure trailer nervous offices of vestibular department are similar among themselves. The receptor device maculae sacculi et utriculi located in the form of several sublime spots is called also otolitovy device (see). On these spots the epithelial cover consists of foot cells — sustentsit (cellulae sustentantes) which do not have relations to transfer of irritation, and the voloskovy (sensornoepitelialny) cells (cellulae pilosae) braided with nerve fibrils and which are not reaching the lower ends of a basal membrane. Shoots of cells, intertwining above among themselves, form the thin fibrous network located parallel to an upper surface of an epithelium and the ends passing directly into an otolitovy membrane (membrana statoconiorum). The last consists of fibrils, kernels and numerous hexagon crystals formed by impregnation of a protein skeleton bicarbonate salt of calcium and magnesium — otoliths, or statoconiums (statoconia). The space between an upper surface of an epithelium and an otolitovy membrane is filled with network from hairs and impregnated with a light body.

Voloskovy cells on an ultramicroscopic structure are subdivided into two types. Cells of the first type have the roundish wide basis, Krom is adjoined by the nerve terminations forming around it a case in the form of a bowl. On their outer surface there is a cuticle. 60 — 80 motionless hairs (stereocilias) length apprx. 40 microns and one mobile kinotsiliya depart from it, 9 peripheral and 2 central fibrilla, beginning from basal little bodies contain edges. Kinotsiliya is always located polarly in relation to a bunch of stereocilias. In cytoplasm of cells mitochondrions and membranes of a cytoplasmic reticulum forming tanks lie. On a surface of membranes ribosomes lie. Cells of the second type have the cylindrical form and on the structure differ from cells of the first type a little, but are more poorly supplied with nerve terminations.

Ultramicroscopic structure of a receptor epithelium of an ampullar comb: I \voloskovy cell of the second type; II \foot cell; III \voloskovy cell of the first type; 1 — hairs of voloskovy cells; 2 — granules in a foot cell; 3 — microvillis of a foot cell; 4 — the nerve terminations having an appearance of a bowl; 5 and 7 — pulpy nerve fibrils; — a kernel of a foot cell; 8 — a basal membrane; 9 — the intracellular mesh device; 10 — mitochondrions of a voloskovy cell.

The nervous device of ampoules of semicircular channels differs from that sacks of a threshold a little. Crista ampullaris in comparison with macula strongly towers over the basis in the form of the narrow truncated cone acting in a gleam of an ampoule. The cone is covered with voloskovy (touch and epithelial) cells, over to-rymi there are jellylike educations — cupula as if got on hairs of an epithelium. In combs the feeling hairs depart from the cells directly up and only at the edges deviate a little and get into cupula covering them, being distributed in it quite evenly. The Otolitovy membrane is absent. Thin structure of voloskovy cells of ampullar combs (fig.) and their innervation almost same, as cells of spots.

Gistol, structure of walls of the webby channel of a snail quite difficult. The vestibular membrane consisting of the connecting fabric covered with the single-layer flat epithelium turned to an endolymph, the endothelium turned to a perilympha is most simply arranged. The outside wall of ductus cochlearis is spliced with a spiral sheaf. Capillaries from the vascular network put in a spiral sheaf which form a considerable thickening — a vascular stripe (stria vascularis) get into it. The lower wall with a nervous epithelium — spiral body — a receptor of acoustical irritations is most difficult arranged (see. Kortiyev body ).

Physiology

In V. at. receptors of acoustical and statokinetic analyzers are located.

The receptor (sound perceiving) device acoustic analyzer (see) is in a snail and it is presented by voloskovy (touch and epithelial) cells of spiral (kortiyev) body. The snail and the receptor device of the acoustic analyzer concluded in it are called the cochlear device. The sound vibrations arising in air are transmitted through outside acoustical pass, a tympanic membrane and a chain of acoustical stones on a vestibular window of a labyrinth, cause wavy movements of a perilympha which, extending, are transferred to spiral body (see. Hearing ). These sloshings are possible thanks to existence of a membrane of a window of a snail, edges at each push of a stirrup and the relevant movement of a perilympha is stuck out towards a drum cavity. Transfer of fluctuations from the environment on fluid mediums of V. at. occurs and directly through bones of a skull (bone sound carrying out). In receptor cells of spiral body there is a transformation of physical energy of sound vibrations to energy of nervous excitement — the nervous impulses coming on conduction department of the acoustic analyzer to its cortical department. With the help elektrofiziol, researches it is established that at sound irritation in a snail there are electric potentials — cochlear currents which on the frequency and a form of fluctuations correspond to the sound vibrations which came to an ear. Cochlear currents after strengthening can be again transformed by means of phone to sound vibrations and in accuracy to repeat the sound which came to an ear. This phenomenon which received the name of microphone effect of a snail, or Uever's phenomenon — Shaving, reflects function of the receptor device of V. at. The curve of cochlear currents (kokhleogramm) which is written down on an oscillograph also allows to judge safety of the receptor device of a snail.

The receptor device of the statokinetic analyzer (see. Vestibular analyzer ), located in semicircular channels and sacks of a threshold, carries the name of a vestibular mechanism. The receptors which are in semicircular channels perceive the angular accelerations arising at turns of the head or rotary motions of all body, and receptors of a threshold react to rectilinear accelerations.

Methods of a research

Modern methods of a research of function B. at. are very difficult and consist in definition of a condition of both of its functions — acoustical and vestibular. At a research of acoustical function the adequate irritant — a sound of various frequency and intensity in the form of true tones, noise and speech signals is applied. As a source of a sound tuning forks, audiometers (tone and speech), the shepotny and loud speech are used. This complex of researches allows to define a condition of function of the sound carrying out system, the receptor device B. at., and also conduction and central departments of the acoustic analyzer (see. Audiometriya ).

At a research of function of a vestibular mechanism define existence of disorders of balance, spontaneous vestibular reactions (see), and also emergence of motive and vegetative reflexes in response to various irritations of a vestibular mechanism (rotary, caloric, galvanic, pressor and other tests). Use of the special equipment gives the chance to objectively estimate a condition of function of a vestibular mechanism with a big accuracy rate (see. Vestibulometriya ).

Pathology

Anomalies of development Century at. meet in the form of total absence of a labyrinth or an underdevelopment of its separate parts. The underdevelopment of spiral body is in most cases noted, is more often than its specific device — voloskovy cells, sometimes the underdevelopment of voloskovy cells of spiral body takes place only on certain sites, at the same time it can be partially kept acoustical function in the form of «islands of hearing». In emergence of inborn defects of V. at. pathological impact on a germ from an organism of mother plays a role, especially in the first months of pregnancy (intoxications, infection, traumatizing a fruit). The known role is played also by genetic factors. It is necessary to distinguish V.'s damages from inborn defects of development at. during a childbed as a result of a prelum of a head of a fruit in the narrow patrimonial ways or obstetric nippers at pathological childbirth.

Bruises in the isolated look in V. at. meet seldom. At fractures of base of the skull the crack can pass through a pyramid of a temporal bone. At cross changes of a pyramid the crack almost always takes V. at., and such change usually is followed by heavy disturbance of acoustical and vestibular functions up to their full fading.

V.'s wounds at. meet at the wounds of a skull which are followed by injury of bones. At the same time get to a zone of damage usually also outside and middle ear. The diagnosis is specified by means of a functional research and a X-ray analysis. Treatment of bruises of V. at. it is carried out by rules of surgical treatment of wounds of a skull. For the purpose of prevention of intracranial complications widely apply antibiotics.

Specific damage of the receptor device of a snail arises at short-term or long influence of sounds of big intensity. Long action of strong noise on V. at. can lead to a professional hearing disorder (see. Acoustic injury , Relative deafness ).

Pathological changes in V. at. arise also at impact on an organism of concussions (see. Vibrotrauma ). At sudden differences of external atmospheric pressure or pressure under water as a result of hemorrhage in V. at. there can occur irreversible changes up to death of receptor cells of spiral body (see. Barotrauma ).

Inflammatory processes arise in V. at., as a rule, for the second time, is more often as a complication acute or hron, purulent average otitis (a timpanogenny labyrinthitis), is more rare — as a result of spread of an infection to V. at. from a subarachnoid space through internal acoustical pass on covers of an eighth cranial nerve at epidemic cerebrospinal meningitis (a meningogenny labyrinthitis). In certain cases in V. at. not microbes, and their toxins get; the inflammatory process developing in these cases proceeds without suppuration (a serous labyrinthitis). The result of purulent process in V. at. always happens full or partial deafness (see); depending on extent of distribution of process after a serous labyrinthitis acoustical function can be recovered partially or completely (see. Labyrinthitis ).

Disturbances of functions Century at. (acoustical and vestibular) can arise at circulatory disturbances and circulation of labyrinth liquids, and also as a result of dystrophic processes. Intoxications, including some medicinal substances (quinine, streptomycin, Neomycinum, Monomycinum, etc.), vegetative and endocrine frustration, diseases of blood and cardiovascular system, a renal failure can be the reasons of such disturbances. Noninflammatory diseases of V. at. combine in the group which received the name labyrinthopathy (see). In some cases the labyrinthopathy proceeds in the form of the repeating attacks of dizziness and the progressing falling of hearing (see. Menyera disease ). At advanced and senile age dystrophic changes in V. at. develop as a result of the general aging of body tissues and disturbance of blood supply of V. at. (see. Presbyacusis ).

V.'s defeats at. can arise at syphilis. At inborn syphilis defeat of the receptor device in the form of a sharp hearing impairment is one of late manifestations and it is found usually at the age of 10 — 20 years. V., characteristic of defeat, at. at inborn syphilis Enneber's symptom — emergence of a nystagmus at increase and pressure decrease of air in outside acoustical pass is considered. At the acquired syphilis V.'s defeat at. arises in the secondary period more often and can sharply proceed — in the form of quickly accruing hearing impairment up to full deafness. Sometimes V.'s disease at. begins attacks of dizziness, a sonitus and suddenly coming deafness. In late stages of syphilis the hearing impairment develops more slowly. V., characteristic of syphilitic defeats, at. more sharply expressed shortening of bone sound carrying out in comparison with air is considered. Defeat of vestibular function at syphilis is observed less often. Dissociation of reactions at rotary and caloric tests is characteristic.

Treatment at syphilitic defeats of V. at. specific. Concerning disorders of functions B. at. specific treatment of subjects is more effective, than earlier it is begun.


Bibliography: Yermolaev V. G. and Levin A. L. Practical audiology, L., 1969, bibliogr.; The multivolume guide to otorhinolaryngology, under the editorship of A. G. Likhachev, t. 1 — 2, M., 1960; H e fi-man L. V. Anatomiya, physiology and pathology of acoustic organs and speech, M., 1970; NDR and c V. F., Temkin Ya. S. and Neumann L. V. have a guide to a clinical audiology, M., 1962, bibliogr.; Zimmerman G. S. Ear and brain, M., 1974; Friedmann I. Pathology of the ear, Oxford, 1974; Hals-Nasen-Ohren-Heil-kunde, hrsg. v. J. Berendes u. a., Bd 3, T. 1 — 2, Stuttgart, 1965 — 1966; Werner G. F. Das Labyrinth, Lpz., 1940, Bibliogr.; W e v e r E.G. L a w r e n-c e M. Physiological acoustics. Princeton, 1954.

M. I. Volfkovich, L. W. Neumann

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