MIDDLE EAR [auris media (PNA); cavum tympani (JNA, BNA)] — the part of an acoustic organ lying between an outside and inner ear and performing the sound carrying out function.
References of separate parts C. at. are available for Alkmeon, Aristotle and Hippocrates. In 16 century G. Fallopy described the drum string passing in a drum cavity, A. Vezaly — a drum cavity, a mastoidal cave and mastoidal cells, and also a hammer and an anvil, G. F. Ingrassia — a stirrup and the muscle straining a tympanic membrane, K. Varoly — a stapedial muscle, B. Evstakhy — the channel connecting a drum cavity to a throat, called in the subsequent an Eustachian tube.
A comparative anatomy
At land vertebral S. at. develops from the branchiate device. The drum cavity and an Eustachian tube are formed of the I branchial aperture (an acoustical pipe, T.), connecting it to a throat. In an outside wall of the branchial aperture adjoining on a cover of a body the tympanic membrane develops. Amphibiouses, reptiles and birds have one acoustical stone — a column (columella).
At crocodiles and birds in the bones surrounding S. at., there are adnexal pneumatic cavities. At a row vtorichnovodny and amphibious, and also at nek-ry turtles and S.'s snakes at. it is partially or completely reduced. Page at. three acoustical stones — a hammer (malleus), an anvil (incus) and a stirrup (stapes) have mammals. The most part of a hammer develops from a ventral (square) cartilage of I - a branchiate arch, the most part of an anvil — from a dorsal (mekkelev) cartilage of the same arch. The dorsal (reykhert) cartilage of the II branchiate arch takes part in formation of a stirrup. At many mammals growth of a drum cavity due to formation of acoustical drums and development of adnexal cavities is observed.
at the beginning of the 2nd month of the pre-natal period in the first pharyngeal sack (the I branchial aperture) is formed pipe and drum deepening. In the subsequent its distal part extends and gives rise to a drum cavity, and a narrow proximal part turns into an Eustachian tube. Cartilaginous laying of acoustical stones is formed in embryonal connecting fabric over primary drum cavity; since 7th month of the pre-natal period the fabric surrounding them is exposed resorptions therefore the drum cavity extends and acoustical stones are suspended in Kay on the lamina of an epithelium. The drum cavity and acoustical stones reach the final sizes at the end of the pre-natal period.
Page at. is located in a temporal bone and its educations are in the close neighbourhood with the large vessels and nerves passing in a base of skull (tsvetn. fig. 1). Page at. consists of the drum cavity filled with air with the acoustical stones located in it, an Eustachian tube, pneumatic cavities and a mastoid.
The drum cavity (cavitas tympanica) represents space about 0,8 — 1 cm3; it is located between tympanic membrane (see) and a bone labyrinth of an inner ear (see). It is reported by means of an Eustachian tube (see. Acoustical pipe ) with a nasal part drinks (see), and through a mastoidal cave (see. Mastoid ) — with mastoidal cells. At the newborn the drum cavity holds in a skull more horizontal position, than at the adult.
In a drum cavity distinguish 6 walls. Upper, pokryshechny, the wall (paries tegmentaiis) is formed by a thin bone plate (a roof of a drum cavity, T.; tegmen tympani) pyramids of a temporal bone. Lower, jugular, the wall (paries jugularis) borders on a jugular pole (fossa jugularis) of a pyramid of a temporal bone, in a cut the upper bulb of an internal jugular vein lies (bulbus v. jugularis sup.). In back, mastoidal, a wall (paries mastoi-deus) there is an entrance to a mastoidal cave (aditus ad antrum). On a medial wall in a cave the ledge of the lateral semicircular channel is located (prominentia canalis semicircularis lat.), below to-rogo there is a ledge of the channel of a facial nerve (a ledge of the front channel, T.; prominentia canalis facialis). In a verkhnemedialny part of a mastoidal wall of a drum cavity the pyramidal eminence (eminentia pyramidalis) is formed, inside to-rogo the stapedial muscle (m. stapedius) lies. The opening in a pyramidal eminence leaves a sinew of this muscle. The front wall of a drum cavity is called sleepy (paries caroticus) since it forms a wall of the sleepy channel, to Krom there goes the internal carotid artery (a. carotis int.). The sleepy wall contains drum cells (cellulae tympanicae); on it the drum opening of an Eustachian tube (ostium tympanicum tubae auditivae) is located. Lateral, webby, the wall (paries membranaceus) is engaged in a most part with a tympanic membrane (membrana tympani).
Medial, or labyrinth, the wall (paries labyrinthicus) is an outside wall of a bone labyrinth (tsvetn. fig. 2). It forms the roundish cape (promontorium), to-ry corresponds to the basis of a snail. Above the cape there is a dimple of a window of a threshold (fossula fenestrae vestibuli) forming a niche with a window of a threshold (fenestra vestibuli), or an oval window in a cut the basis of a stirrup enters. Below the cape in a nisheobrazny dimple of a window of a snail (fossula fenestrae cochleae) the window of a snail (fenestra cochleae), or a round window is located. It is closed by a secondary tympanic membrane (membrana tympani secundaria) and conducts to a drum ladder (scala tympani). The form of a dimple of a window of a snail and the window is individually changeable.
The drum cavity is conditionally divided into three departments: lower, average and upper. The lower part, gipotimpanum (hypotympanum), represents the part of a drum cavity located between a jugular wall and bottom edge of a tympanic membrane. The average department, mezotimpanum (mesotympanum), is limited by two horizontal planes which are conditionally carried out through the lower and upper edges of a tympanic membrane. The upper part, epitim-panum (epitym panum), is between the upper edge of a tympanic membrane and a roof of a drum cavity.
Acoustical stones (ossicula auditus) lie in an upper part of a drum cavity. They become stronger sheaves and connect with each other joints, forming a mobile three-membered chain between a tympanic membrane and a window of a threshold (fig. 1). At newborns around acoustical stones a part of connecting fabric therefore their mobility is limited approximately up to 6 months of the post-natal period remains.
The form of stones is individually changeable. Acoustical stones of the right and left S. at. often have the unequal form and the sizes.
The hammer (malleus) represents an outside link of this chain. In it distinguish a head (caput mallei), the handle (manubrium mallei) and two shoots — a thin, long front shoot (processus ant.) and short lateral shoot (processus lat.). The lower end of the handle of a hammer is spliced with a tympanic membrane, the front shoot enters a stony and drum crack (fissura petrotympanica), the lateral shoot adjoins to a tympanic membrane. The hammer is fixed by front, upper and lateral sheaves (ligg. mallei ant., sup. et lat.).
The anvil (incus) is an average chain link of acoustical stones. It consists of a body (corpus incudis) and two legs (long and short). The body of an anvil has a joint surface, forms edges with a joint surface of a hammer-kovalnemolotochkovy on a joint (art. incudomallearis). The long leg (crus longum) has the bent end, on Krom there is a lenticular shoot (processus lenticularis) which is jointed with a stirrup. The short leg (crus breve) connects by means of a sheaf to a back wall of a drum cavity.
The stirrup (stapes) forms an internal chain link of acoustical stones. It consists of a head (caput stapedis), front and back legs (crura ant. et post.) and bases (basis stapedis). The head of a stirrup forms with a lenticular shoot of an anvil nakovalnestremenny a joint (art. incudostapedia). Both legs together with the basis of a stirrup limit an opening, in Krom there is a membrane of the stapes (membrana stapedis). The basis of a stirrup is fixed in a window of a threshold by a ring sheaf (lig. annulare stapedis). In this sheaf allocate the front, back and lateral parts differing with a direction of fiber.
The movements of acoustical stones are regulated by the muscle straining a tympanic membrane (m. tensor tympani) and a stapedial muscle (m. stapedius).
The mucous membrane of a drum cavity covers all educations located in it and proceeds in a mucous membrane of an Eustachian tube and mastoidal cells (tsvetn. fig. 3). Passing to acoustical stones, the mucous membrane forms folds — front and back molotochkovy (plicae malleolares ant. et post.), fold of an anvil (plica incudis) and fold of a stirrup (plica stapedis). In the place of passing of a drum string the fold of a drum string (plica chordae tympani) is formed.
Supratympanic deepening, or attic (recessus epitympanicus, s. at-ticus), has the form of a dome and stretches from a roof of a drum cavity to a sinew of the muscle straining a tympanic membrane. In it the head of a hammer and a body of an anvil lie. Front deepening of a tympanic membrane (recessus membranae tympani ant.) is between a tympanic membrane and a front linking of a hammer. Back deepening (recessus membranae tympani post.) it is located between a tympanic membrane and a back linking of a hammer. Upper deepening (recessus membranae tympani sup.), or prussakovo the space, lies between a head of a hammer, a body of an anvil and a loose part (pars flaccida) of a tympanic membrane.
Innervation. The mucous membrane of a drum cavity, an Eustachian tube and mastoidal cells is innervated by a drum texture (plexus tympanicus) located on a labyrinth wall of a drum cavity (tsvetn. fig. 4). This texture supports small groups of multipolar neurons; it is formed by a drum nerve (n. tympanicus) which is a branch of a glossopharyngeal nerve, a connecting branch of a facial nerve (r. communicans) and caroticotympanic nerves (nn. caroticotympanici) departing from an internal sleepy texture (plexus caroticus int.). The muscle straining a tympanic membrane is innervated by a branch of a mandibular nerve (n. musculi tensoris tympani), a stapedial muscle — a branch of a facial nerve — a stapedial nerve (n. stapedius).
Blood supply Page at. carry out arteries: lower drum (. tympanica inf.), branching off from ascending pharyngeal (a. pharyngea ascendens), stylomastoid (a. stylomastoidea) and back drum (a. tympanica post.) — from back ear (a. auricularis post.), lobby drum (. tympanica ant.) — from maxillary (a. maxillaris), upper drum (a. tympanica sup.) — from average meningeal (a. meningea media) and caroticotympanic arteries (aa. caroticotympanicae) — from an internal carotid artery. Venous outflow happens on drum veins (vv. tympanicae) in a krylovidnovenozny texture [plexus (venosus) pterygoideus].
Lymph drainage it is carried out on limf, to the vessels suitable to mastoidal, retropharyngeal and deep parotid limf, to nodes (nodi lymphatici mastoidei, retropha-ryngeales et parotidei profundi).
As the sound carrying out part of body hearing (see), S. at. carries out transfer of sound vibrations from the environment to to the acoustic analyzer (see). The sound wave causes fluctuations of a tympanic membrane, to-rye through a chain of acoustical stones are transformed and transferred to the basis of a stirrup; the synchronous movement of a stirrup causes the fluctuations of a perilympha which are transferred on kortiyev body (see) and transformed to nervous impulses. Copular and muscular system C. at. plays also protective role, protecting an inner ear from subthreshold and superthreshold sound vibrations. Pneumatic system of cells of S. at. plays a role of the resonator of sound waves.
The Eustachian tube equalizes pressure in a drum cavity with atmospheric pressure. The ciliary epithelium covering it bears protective function, protecting a middle ear from penetration of contagiums from a nasopharynx.
Methods of a research
by the Main method of a research C. at. is otoskopiya (see). The direct otoskopiya at the unimpaired tympanic membrane gives the chance to judge indirectly S.'s condition at. At the same time thinning and blueness of a tympanic membrane at an otosclerosis come to light, localization of its hyperemia and infiltration, and also an overhang of a posterosuperior wall of outside acoustical pass at acute and hron. purulent average otitis, availability of exudate in a drum cavity at exudative otitis. At limited, subtotal and total defects of a tympanic membrane by means of an otoskopiya it is possible to estimate directly character and degree of pathology of S. at. For more detailed otoskopichesky diagnosis use optical devices — Zigle's funnel (see. Zigle funnel ), special magnifying glasses (see. Magnifying glass ), operative microscope (see). One of diagnostic manipulations is tympanopuncture (see).
Functional researches of the sound carrying out system C. at. definition of auditory acuity by means of shepotny and informal conversation, kamertonalny tests, superthreshold and subthreshold are audiometriya (see).
By important method of a research C. at. is radiological — a X-ray analysis of a temporal bone in side (according to Schueller), a braid (on Stenversa) and axial (according to Maier) projections (fig. 2). Schueller's way gives information on a condition of various departments of an ear and is made as a survey picture. On it it is possible to judge a pnevmatization of a mastoid and a scaly part of a temporal bone, a mastoidal cave, size of openings of internal acoustical pass, its walls, etc. The slanting projection on Stenversa is an additional way for a research only of nek-ry details of a pyramid (a stony part) of a temporal bone; it is a maloinformativna at pathology of a middle ear. The axial projection according to Maier also serves in the additional way, however is used much more often at S.'s diseases at., than way Step-versa. In this situation x-ray emission is directed along an axis of a pyramid that allows to receive the image of important anatomic details of a drum cavity — acoustical stones, supratympanic deepening (attic), a sigmoid sine. The most informative for the image of a drum cavity is tomography (see) in a direct (back) projection, at a cut on the tomogram both temporal bones are visible.
S.'s Pathology at. includes malformations, damages, diseases and tumors.
Malformations Page at. are, as a rule, combined with anomalies of development outside ear (see) also occur approximately at 1 of 10 000 newborns (more often at boys). They are divided into a hypogenesis, a dysgenesis and the mixed forms. On extensiveness defect can be various — from small defects of acoustical stones to an anotiya (lack of an auricle). At a hypogenesis elements of an outside ear either are absent, or are in a rudimentary state. At rentgenol. a research reveal absence or an underdevelopment of outside acoustical pass and a drum part of a temporal bone. As a rule, temporal bone in general several gipoplazirovan; a drum cavity, an Eustachian tube and the aircontaining structures of mastoidal appendages of S. at. are developed well. Acoustical stones rudimentary, are soldered in the uniform block, nakovalnestremenny the joint is absent. The labyrinth wall of a drum cavity is not changed, windows of a threshold and a snail function; the plate of the basis of a stirrup is mobile. At a research of hearing reveal its decrease to 50 — 70 dB on the sound carrying out type.
At a dysgenesis the rudiment of an auricle is presented by all its main anatomic departments, but they are considerably deformed. Cartilaginous and bone departments of outside acoustical pass are available, but the last sharply is concentrically narrowed (to dot). Tympanic membrane rudimentary. Temporal bone, and in some cases and face bones (facial skeleton) of a gipoplazirovana. The temporal bone is badly pneumatitized, the drum cavity and a mastoidal cave of the small sizes, are deformed, acoustical stones rudimentary, soldered. It is often noted patol. underdevelopment of elements of a labyrinth wall, basis of a stirrup, windows of a threshold and snail. Decrease in hearing is noted, degree of manifestation to-rogo depends on anatomic changes of elements C. at.
Treatment of inborn defects of S. at. operational. At local malformations of elements of a drum cavity defect is eliminated by means of one of receptions tympanoplasties (see). In the absence of also cartilaginous and bone departments of outside acoustical pass make aurikulomeatotimpano-plastics (see. Otoplasty ).
The forecast depends on extent of damage of an inner ear.
Damages can be a consequence of an injury of S. at. through outside acoustical pass or injuries of bones of a skull with disturbance of an integrity of a tympanic membrane. A wedge, symptoms of damage of S. at. the otorrhagia and decrease in hearing are. In the acute period carry out the conservative treatment directed to the prevention of an inflammation of S. at. — make antiseptic processing of outside acoustical pass and a tympanic membrane, appoint antibiotics. In cases when the expressed decrease in hearing remains in the late posttraumatic period, an operative measure is shown (see. Otoplasty ).
Diseases. The most frequent diseases of S. at. are acute and hron. inflammations (see. Otitis ). Tubo-otitis (see) — a special form of average otitis with preferential disturbance of ventilating function of an Eustachian tube. Acute average otitis, catarral or purulent, can arise as an independent disease or as a complication at inf. diseases or injury of a tympanic membrane. Purulent average otitises sometimes are followed by heavy intracranial and septic complications. The investigation postponed earlier acute or hron. otitis adhesive otitis is. Its wedge, manifestations — the continuous or progressing decrease in hearing and cicatricial changes of a tympanic membrane. Radiological acute and hron. inflammatory processes of S. at. are characterized by blackout of an attic, destruction of its outside wall and acoustical stones. Otitises can lead to disturbance of anatomical structures of S. at., to development relative deafness (see) and to deafness (see). The main method of the treatment directed to improvement or recovery of hearing is operational (see. Tympanosclerosis ).
Tumors. To benign tumors of S. at. carry fibroma (see), a neurofibroma (see), myxoma (see), to-rye meet extremely seldom. Rather high-quality current characterizes a glomal tumor of S. at. (see. Glomal tumors ). From malignant tumors of S. at. are observed cancer (see) and sarcoma (see).
Operations at S.'s diseases at. have two main objectives: elimination of a suppurative focus at otitis and its intracranial complications; improvement or recovery of acoustical function. Carry to the first group of interventions antropunktion (see), an antrotomy (see. Mastoiditis ), radical operation of a middle ear and an attikoantrotomiya (see Otitis). The group hearing of the improving operations includes various options tympanoplasties (see) and stapedoplasties (see. Otosclerosis ).
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C.H. Lapchenko; T. F. Rostovtseva (rents.), V. S. Speransky (An., comparative anatomy, embr.).