The structure of the human ear. Middle ear

26.04.2020

The ear is divided into three sections: outer, middle and inner. The outer and middle ear conduct sound vibrations to the inner ear and are a sound-conducting apparatus. The inner ear forms the organ of hearing and balance.

Outer ear consists of the auricle, external auditory canal and tympanic membrane, which are designed to capture, conduct sound vibrations to the middle ear.

Auricle consists of elastic cartilage covered with skin. Only the earlobe is missing cartilage. The free edge of the shell is wrapped, and is called the curl, and the antihelix is \u200b\u200blocated parallel to it. At the front edge of the auricle, a protrusion is distinguished - a tragus, and an antigus is located behind it.

External ear canal is a short S-shaped curved canal 35-36 mm long. Consists of a cartilaginous part (1/3 of the length) and bone (the remaining 2/3 of the length). The cartilaginous part passes into the bone at an angle. Therefore, when examining the ear canal, it must be straightened.

The outer ear canal is lined with skin containing sebaceous and sulfur glands that secrete sulfur. The passage ends with an eardrum.

Eardrum -it is a thin, translucent oval plate that sits at the border of the outer and middle ear. It stands obliquely in relation to the axis of the external auditory canal. Outside, the eardrum is covered with skin, and inside it is lined with mucous membrane.

Middle ear includes the tympanic cavity and the auditory (Eustachian) tube.

Tympanic cavity located in the thickness of the pyramid temporal bone and is a small cuboid space with a volume of about 1 cm 3.

From the inside, the tympanic cavity is lined with mucous membrane and filled with air. It contains 3 auditory ossicles; malleus, incus and stapes, ligaments and muscles. All bones are interconnected by means of a joint and are covered with a mucous membrane.

The hammer is spliced \u200b\u200bwith the tympanic membrane by its handle, and the head is connected to the incus, which in turn is movably connected to the stapes.

Value auditory ossicles consists in the transmission of sound waves from the eardrum to the inner ear.

The tympanic cavity has 6 walls:

1. Upper the tegmental wall separates the tympanic cavity from the cranial cavity;

2. Lower the jugular wall separates the cavity from the outer base of the skull;

3. Anterior carotid separates the cavity from the carotid canal;

4. Posterior mastoid wall separates the tympanic cavity from the mastoid process

5. Lateral wall is the eardrum itself

6. Medial wall separates the middle ear from inner ear... It has 2 holes:

- oval - the window of the vestibule, covered with a stirrup.

- round - the window of the cochlea, covered with a secondary tympanic membrane.

The tympanic cavity using auditory tube communicates with the nasopharynx.

Auditory tube - this is a narrow channel approximately 35 mm long and 2 mm wide. Consists of cartilaginous and bone parts.

The auditory tube is lined with ciliated epithelium. It serves to supply air from the pharynx into the tympanic cavity and maintains the pressure in the cavity, the same as the external one, which is very important for the normal operation of the sound-conducting apparatus. Infection can pass through the auditory tube from the nasal cavity to the middle ear.

Inflammation of the auditory tube is called eustachite.

Inner earlocated in the thickness of the temporal bone pyramid and separated from tympanic cavity its medial wall. It includes a bone labyrinth and a membranous labyrinth inserted into it.

Bone labyrinth is a system of cavities and consists of 3 sections: vestibule, cochlea and semicircular canals.

The vestibuleis a cavity of small size and irregular shape, occupying a central position. It communicates with the tympanic cavity through an oval and round opening. In addition, there are 5 small holes in the vestibule, through which it communicates with the cochlea and semicircular canals.

Snail is a convoluted spiral channel that forms 2.5 turns around the axis of the cochlea and ends blindly. The axis of the cochlea lies horizontally and is called the cochlear bone shaft. A bony spiral plate is wrapped around the rod.

Semicircular canals - are represented by 3 arcuate tubes lying in three mutually perpendicular planes: sagittal, frontal, horizontal.

Webbed labyrinth - is located inside the bone, resembles it in shape, but has a smaller size. The wall of the membranous labyrinth consists of a thin connective tissue plate covered with squamous epithelium. Between the bony and membranous labyrinth, there is a space filled with fluid - perilymph. The membranous labyrinth itself is filled endolymph and represents closed system cavities and channels.

In the membranous labyrinth, elliptical and spherical sacs, three semicircular ducts and a cochlear duct are distinguished.

Elliptical pouch five holes communicates with the semicircular duct, and spherical - with cochlear duct.

On the inner surface spherical and elliptical sacs (uterus) and semicircular ducts have hair (sensitive) cells covered with a jelly-like substance. These cells perceive vibrations of the endolymph during movements, turns, tilts of the head. The irritation of these cells is transmitted to the vestibule part of VIII couples FMN, and then to the nuclei of the medulla oblongata and cerebellum, then to the cortical region, i.e. into the temporal lobe of the large brain.

On a surface sensitive cells there are a large number of crystalline formations consisting of calcium carbonate (Ca). These formations are called otoliths... They are involved in the excitation of hair sensitive cells. When the position of the head changes, the pressure of the otoliths on the receptor cells changes, which causes their excitation. Hair sensitive cells (vestibuloreceptors), spherical, elliptical sacs (or uterus) and three semicircular ducts make up vestibular (otolith) apparatus.

Cochlear duct has a triangular shape and is formed by the vestibular and main (basilar) membranes.

On the walls of the cochlear duct, namely on the basilar membrane, there are receptor hair cells (auditory cells with cilia), the vibrations of which are transmitted to the cochlear part of the VIII pair of FMN, and then along this nerve the impulses reach the auditory center located in the temporal lobe.

In addition to hair cells on the walls of the cochlear duct, there are sensory (receptor) and supporting (supporting) cells that perceive perilymph vibrations. The cells on the wall of the cochlear duct form the auditory spiral organ (organ of Corti).

The ear is considered the most complex organ in the human body. It allows you to perceive sound signals and controls the position of a person in space.

Anatomical structure

The organ is paired, and it is located in the temporal region of the skull, in the area of \u200b\u200bthe pyramidal bone. Conventionally, the anatomy of the inner ear can be divided into three main areas:

The inner ear, made up of several dozen elements.
Middle ear. This part includes the tympanic cavity (membrane) and special ossicles (the smallest bone in the human body).
Outer ear. Consists of the external auditory canal and auricle.

The inner ear includes two labyrinths: membranous and bony. The bony labyrinth consists of elements that are hollow inside, connected to each other. The labyrinth is perfectly protected from outside influences.

A membranous labyrinth, identical in shape, but smaller in size, is placed inside the bone labyrinth.

The inner ear cavity is filled with two fluids: perilymph and endolymph.

Perilymph is used to fill the inter-labyrinth cavities.
Endolymph is a thick, transparent liquid that is present in the membranous labyrinth and circulates through it.

The inner ear has three parts:

snail,
the threshold;
semicircular canals.

The structure of the semicircular canals begins from the center of the labyrinth - this is the vestibule. At the back of the ear, this cavity is connected to the semicircular canal. On the side of the wall there are "windows" - the internal openings of the cochlear canal. One of them is connected to the stapes, the second, which has an additional tympanic membrane, communicates with the spiral canal.

The structure of the snail is simple. The spiral bone plate is located along the entire length of the cochlea, dividing it into two sections:

drum ladder;
entrance staircase.

The main feature of the semicircular canals is that they have legs with ampoules expanding at the end. The ampoules are close to the sacs. On the eve of the fused anterior and posterior canals come out. The vestibular cochlear nerve serves to transmit nerve impulses.

Functions

Scientists have found that the structure of the inner ear has also changed with the process of evolution. In the body modern man the inner ear will serve two purposes.

Orientation in space. The vestibular apparatus located inside the auricle helps a person navigate the terrain and keep the body in the desired position.

This will involve the circular canals and the vestibule.

Hearing. Inside the snail, processes take place that are responsible for the perception of sound signals by the brain.

Perception of sounds and orientation

The tremors of the eardrum are caused by the movement of the endolymph. The peralymph that moves up the stairs also affects the perception of sound. The vibrations irritate the hair cells of Corti's organ, which converts the audible sound signals directly into nerve impulses.

The human brain receives information and analyzes it. Based on the information received, a person hears a sound.

The vestibular apparatus is responsible for the position of the body in space. Roughly speaking, it acts like a building level used by workers. This organ helps maintain the balance of the body. The vestibule and semicircular canals have a very complex systematic structure; inside them there are special receptors called scallops.

It is the scallops that sense and respond to head movements. In this they resemble the hair cells found in the cochlea. Irritation occurs due to the presence of a jelly-like substance in the scallops.

If orientation in space is necessary, the receptors in the vestibule sacs come into activity. Linear acceleration of the body induces the endolymph to move, which irritates the receptors. Then, information about the beginning of the movement enters the human brain. Now there is an analysis of the information received. In the event that the information received from the eyes and from the vestibular apparatus is different, the person experiences dizziness.

Hygiene is essential for the proper functioning of the inner ear. It is the timely cleaning of the ear canal from sulfur that will keep hearing in good condition.

Possible diseases

Diseases of the auricle decrease a person's hearing, and also prevent the vestibular apparatus from working correctly. In the event that damage is caused to the cochlea, sound frequencies are perceived, but incorrectly. Human speech or street noise is perceived as a cacophony of different sounds. This state of affairs not only makes it difficult for your hearing to function properly, it can also lead to serious injury.

The ear cochlea can suffer not only from harsh sounds, but also from the effect of an airplane taking off, a sharp immersion in water, and many other situations.

In this case, damage to the eardrum will occur and. Thus, a person can lose hearing either for a long period, in more severe cases - for life. In addition, other troubles related to the inner ear may occur.

Dizziness can have both independent and possible causes.

This disease not fully investigated and its causes are unclear, but the main symptoms are periodic dizziness, accompanied by clouding of auditory function.

Lop-ear... Despite the fact that this is a cosmetic nuance, many are puzzled by the problem of correcting protruding ears. In order to get rid of this ailment, plastic surgery is performed.

Due to damage to bone tissue (its growth), there is a decrease in the sensitivity of the ear, the occurrence of noise, and a decrease in auditory function.

They call acute or chronic inflammation of the auricle, provoking a violation of its functioning.

Most "ear diseases" can be cured by observing. But, in the event of inflammatory processes, the consultation of the attending physician or an ENT specialist is required.

Video: Inner Ear

Behind and up from the cape is niche of the vestibule window (fenestra vestibuli),resembling an oval in shape, elongated in the anteroposterior direction, measuring 3 by 1.5 mm. The vestibule window is closed basis of the stirrup (basis stapedis),attached to the edges of the window

Figure: 5.7.The medial wall of the tympanic cavity and the auditory tube: 1 - cape; 2 -strip in the niche of the vestibule window; 3 - snail window; 4 - the first knee of the facial nerve; 5 - ampulla of the lateral (horizontal) semicircular canal; 6 - drum string; 7 - stapes nerve; 8 - jugular vein; 9 - internal carotid artery; 10 - auditory tube

through annular ligament (lig.annulare stapedis).In the area of \u200b\u200bthe rear-lower edge of the cape there is snail window niche (fenestra cochleae),protracted secondary tympanic membrane (membrana tympani secundaria).The niche of the snail window faces the posterior wall of the tympanic cavity and is partially covered by the protrusion of the posterior lower slope of the promontorium.

The horizontal knee of the facial nerve passes directly above the window of the vestibule in the bony fallopian canal, and the protrusion of the ampulla of the horizontal semicircular canal is located above and posteriorly.

Topography facial nerve (n. facialis, VII cranial nerve)is of great practical importance. Joining together with n. statoacusticusand n. intermediusinto the internal auditory canal, the facial nerve runs along its bottom, in the labyrinth it is located between the vestibule and the cochlea. In the labyrinthine section, the secretory portion of the facial nerve departs large stony nerve (n. petrosus major),innervating the lacrimal gland, as well as the mucous glands of the nasal cavity. Before entering the tympanic cavity above the upper edge of the window of the vestibule there is geniculate ganglion (ganglion geniculi),in which the taste sensory fibers of the intermediate nerve are interrupted. The transition from the labyrinthine to the tympanic section is indicated as the first knee of the facial nerve.The facial nerve, reaching the protrusion of the horizontal semicircular canal on the inner wall, at the level pyramidal eminence (eminentia pyramidalis)changes its direction to vertical (second knee),passes through the styloid canal and through the hole of the same name (for. stylomastoideum)goes to the base of the skull. In the immediate vicinity of the pyramidal eminence, the facial nerve gives a branch to stapes muscle (m. stapedius),here from the trunk of the facial nerve departs drum string (chorda tympani).It passes between the malleus and the incus through the entire tympanic cavity from above the eardrum and exits through fissura petrotympanica (s. Glaseri),giving taste fibers to the anterior two-thirds of the tongue on its side, secretory fibers to salivary gland and fibers to the nerve vascular plexuses. The wall of the canal of the facial nerve in the tympanic cavity is very thin and often has dehiscence, which determines the possibility of the spread of inflammation from the middle ear to the nerve and the development of paresis or even paralysis of the facial nerve. Various options for the location of the facial nerve in the tympanic and mastoid

The middle ear is an integral part of the ear. Occupies the space between the external auditory organ and the eardrum. Numerous elements are involved in its structure, which have certain features and functions.

Structural features

The middle ear is made up of several important elements. Each of these components has structural features.

Tympanic cavity

This is the middle part of the ear, very vulnerable, often subject to inflammatory diseases. It is located behind the eardrum, before reaching the inner ear. Its surface is covered with a thin mucous membrane. It has the shape of a prism with four irregular edges and is filled with air inside. Consists of several walls:

The outer wall with a webbed structure is formed by the inner part of the tympanic membrane, as well as the bone of the ear canal.
The inner wall has a recess on top, in which the window of the vestibule is located. It is a small oval hole, which is covered by the lower surface of the stirrup. Below it is a promontory along which a furrow runs. Behind it is a funnel-shaped dimple in which the snail window is placed. From above, it is limited by a bone roller. There is a tympanic sinus above the snail window, which is a small depression.
The upper wall, which is called the tectum, as it is formed by solid bone substance and protects it. The deepest part of the cavity is called domed. This wall is necessary to separate the tympanic cavity from the walls of the skull.
Bottom wall - jugular, as it participates in the creation of the jugular fossa. It has an uneven surface, as it contains drum cells that are necessary for air circulation.
The posterior mastoid wall contains an opening that leads into the mastoid cavity.
The anterior wall has a bony structure and is formed by substance from the canal carotid artery... Therefore, this wall is called sleepy.

Conventionally, the tympanic cavity is divided into 3 sections. The lower one is formed by the lower wall of the tympanic cavity. The middle is the bulk, the space between the top and bottom border. The upper section is the part of the cavity corresponding to its upper border.

Auditory bones

They are located in the area of \u200b\u200bthe tympanic cavity and are important, since without them it would be impossible sound perception... These are the hammer, anvil and stirrup.

Their name comes from the corresponding form. They are very small in size and are lined with a mucous membrane outside.

These elements connect with each other, forming real joints. They have limited mobility, but allow you to change the position of the elements. They are connected to each other as follows:

The hammer has a round head that connects to the handle.
The incus has a rather massive body, as well as 2 processes. One of them is short, rests against the fossa, and the second is long, directed to the handle of the hammer, thickened at the end.
The stapes includes a small head, covered with articular cartilage from above, serves to articulate the incus and 2 legs - one straight, and the second more curved. These legs are attached to an oval plate contained in the vestibule window.

The main function of these elements is the transmission of sound impulses from the membrane to the oval window of the vestibule... In addition, these vibrations are amplified, which makes it possible to transmit them directly to the perilymph of the inner ear. This is due to the fact that the ossicles are articulated in a lever manner. In addition, the size of the stapes is many times smaller than the eardrum. Therefore, even the smallest sound waves allow you to perceive sounds.

Muscle

The middle ear also has 2 muscles - they are the smallest in human body... The muscular abdomen are located in the secondary cavities. One serves to strain the tympanic membrane and is attached to the handle of the hammer. The second is called the stirrup and is attached to the head of the stirrup.

These muscles are necessary to maintain the position of the auditory ossicles, regulate their movements. This makes it possible to perceive sounds of varying strength.

Eustachian tube

The middle ear connects to the nasal cavity through the Eustachian tube. It is a small canal, about 3-4 cm long. On the inside, it is covered with a mucous membrane, on the surface of which there is a ciliated epithelium. The movement of his cilia is directed towards the nasopharynx.

It is conventionally divided into 2 parts. The one that is adjacent to the ear cavity has walls with bone structure... And the part adjacent to the nasopharynx has cartilaginous walls. In the normal state, the walls are adjacent to each other, but when the jaw moves, they diverge in different directions. Due to this, air flows freely from the nasopharynx into the organ of hearing, providing the same pressure within the organ.

Due to the close proximity to the nasopharynx, the Eustachian tube is prone to inflammatory processes, since the infection can easily enter it from the nose. Its patency may be impaired in case of colds.

In this case, the person will experience congestion, which brings some discomfort. To deal with it, you can do the following:

Examine the ear. An unpleasant symptom can be caused by an ear plug. You can delete it yourself. To do this, drip a few drops of peroxide into the ear canal. After 10-15 minutes, the sulfur will soften, so it can be easily removed.
Move the lower jaw. This method helps with mild congestion. Need to push lower jaw forward and move it from side to side.
Apply the Valsalva method. Suitable when ear congestion persists for a long time. It is necessary to close the ears and nostrils, take a deep breath of air. You need to try to exhale it with your closed nose. The procedure should be carried out very carefully, as during it it may change arterial pressure and speed up your heartbeat.
Use the Toynbee method. You need to fill your mouth with water, pinch the ear holes and nostrils, take a sip.

The eustachian tube is very important, as thanks to it, normal pressure in the ear. And when it is blocked by various reasons this pressure is disturbed, the patient complains of tinnitus.

If, after carrying out the above manipulations, the symptom does not go away, you should consult a doctor. Otherwise, complications may develop.

Mastoid

This is a small bone formation, convex above the surface and shaped like a papilla. Located behind the auricle. It is filled with numerous cavities - cells connected to each other by narrow slits. The mastoid is necessary to improve the acoustic properties of the ear.

Main functions

The following functions of the middle ear can be distinguished:

Sound conduction. With its help, sound is delivered to the middle ear. The outer part captures sound vibrations, then they pass through the auditory canal, reaching the membrane. This causes it to vibrate, which affects the ossicles. Through them, vibrations are transmitted to the inner ear through a special membrane.
Even distribution of pressure in the ear. When atmospheric pressure is very different from that in the middle ear, it is equalized through the Eustachian tube. Therefore, when flying or when immersed in water, the ears are temporarily blocked, as they adapt to new pressure conditions.
Safety function. The middle part of the ear is equipped with special muscles that protect the organ from injury. At very strong sounds, these muscles reduce the mobility of the auditory ossicles to a minimum level. Therefore, the membranes do not rupture. However, if strong sounds are very harsh and sudden, the muscles may not be able to complete their functions. Therefore, it is important to beware of such situations, otherwise you can partially or completely lose your hearing.

Thus, the middle ear performs very important functions and is an integral part of the auditory organ. But it is very sensitive, so it should be protected from negative influences.... Otherwise, various diseasesleading to hearing impairment.

Eardrum is located at the end of the tympanic part of the temporal bone pyramid at an angle of 30 ° with respect to the lower wall of the external auditory canal. In a newborn, the tympanic membrane lies at an angle of 12 0 almost horizontally, which is associated with the later development of the bone of the tympanic part of the pyramid. Fig. 6 General location of the outer, middle and inner ear in the temporal bone pyramid.

The tympanic part of the temporal bone.

The tympanic membrane is translucent, very thin, about 0.1 mm, pearl gray in color, has an almost round shape, since the vertical size of the tympanic membrane is about 0.9 cm - 1 cm, horizontally - 0.8 - 0.9 cm ., the area of \u200b\u200bthe tympanic membrane is about 60 mm 2.

Top part tympanic membrane relaxed, folded, since it consists of two layers: from the side of the external auditory canal it is covered with the epidermis, and from the side of the tympanic cavity with epithelium. Above, the tympanic membrane is attached to the uneven bones of the pyramid and the external process of the malleus is woven into it from the tympanic cavity. On the outer surface of the upper part of the tympanic membrane, it shines through with a yellowish granule, with two folds extending from it. The folds are a conditional border that separates the upper, relaxed part of the tympanic membrane, which is only 10% of the area of \u200b\u200bthe tympanic membrane, from the lower, stretched part. Figure: 7 Left tympanic membrane. Figure: 8. Right tympanic membrane.

At the bottom, stretchedparts to two layers of the tympanic membrane is added a layer consisting of connective tissue with circular and radial, elastic fibers, cobweb-shaped, and giving special strength to the stretched part of the tympanic membrane.

The stretched part of the tympanic membrane is much more relaxed, it makes up more than 90% of the area of \u200b\u200bthe tympanic membrane, and with the help of fibrous fibers of connective tissue, it is attached and stretched to a special bone groove along the lower edge of the bony external auditory canal. In the stretched part, the tympanic membrane is tightly adhered to the handle of the malleus, which appears as a pale yellowish strip extending from the outer process of the malleus to the center and slightly posteriorly.

For the right tympanic membrane, the upper end of the hammer handle is at 13 o'clock. And for the left eardrum at 11 o'clock. The lower end of the hammer handle is called the umbilicus of the membrane. In this part, the eardrum in the form of a cone is drawn into the tympanic cavity, and the navel corresponds to the apex of the cone.

Since the tympanic membrane ruptures during inflammation - perforation, it is conventionally divided into four parts to indicate the site of the perforation. Division is carried out by means of two imaginary lines, one of which runs along the handle of the hammer, and the other through the navel at a right angle. The anterior half of the tympanic membrane is divided into two quadrants: anterior - upper and anterior - lower. Accordingly, the posterior half to the posterior - upper and posterior - lower quadrants. With the help of such division, it is possible, if necessary, to clarify the place of rupture (perforation) of the tympanic membrane.

Examinethe eardrum using a special concave mirror, a light source, and an ear funnel, which is inserted into the cartilaginous part of the external auditory canal, having previously pulled the auricle to straighten the spiral bend of the external auditory canal. A light spot appears on the mirror surface of the membrane, in the form of a triangle, the apex of which is located at the navel, and the base on the anterior lower quadrant of the tympanic membrane. This is the so called light cone, which is always visible on a healthy tympanic membrane and is absent in its pathology.

The eardrum is pierced with endings tympanic nervewhich departs from lower, sensory node of the glossopharyngeal nerve, immediately after leaving the cranial cavity, and therefore, it is extremely sensitive, and its inflammation causes severe pain.

Behind the eardrum is the tympanic cavity with middle ear,which is his central part... The middle ear occupies the entire pyramid of the temporal bone, and consists of tympanic cavity, auditory tube and mastoid process.

General form outer, middle and inner ear.

Tympanic cavity,being the central part of the temporal bone pyramid and the central part of the middle ear, it is a narrow, bony cleft filled with air, with a volume of about 1 - 2 cm 3, similar to a drum, or a tambourine, placed on the edge, and inclined towards the external auditory canal.

Outer wall tympanic cavity is eardrum, and inner wallthe tympanic cavity is the outer wall inner ear with two windows, closed membranes Due to the presence of membranes on both sides, this narrow cavity is called the tympanic cavity.

Superior bony wall of the tympanic cavity or roofis both the front wall of the pyramid of the temporal bone, and separates the tympanic cavity from the middle cranial fossa, where the temporal lobe of the brain is located. In children early age at the junction of the pyramid and the scaly part of the temporal there is a gap, which subsequently overgrows connective tissue... Such a close location of the tympanic cavity to the middle cranial fossa can be the cause of inflammatory lesions of the temporal lobe of the brain in chronic processes in the tympanic cavity. Fig. 9 Bony walls of the tympanic cavity.

The lower bone wall of the tympanic cavity,being the lower wall of the temporal bone pyramid, it borders on the outer base of the skull, where a thickened jugular vein or bulb of the jugular vein is located in the bone cavity. Inflammation of the tympanic cavity, causing damage to bone tissue, penetrates the vascular wall of the bulb of the jugular vein and contributes to the formation of a thrombus. The resulting thrombus impedes the outflow of venous blood from the skull and is one of the most severe complications chronic inflammation middle ear

The lower wall of the temporal bone pyramid.

1 External auditory canal. 2 Styloid process. 3 The tympanic part of the temporal bone pyramid. 4 Mandibular fossa. 5 Deepening of the pyramid 6 Zygomatic process. 7,8,9 A gap between the stony and scaly parts. 10 Semi-canal of the auditory tube and muscle stretching the eardrum. 11 Internal opening of the carotid canal. 12 External opening of the carotid canal. 13 Fovea of \u200b\u200bthe pyramid. 14 Opening of the canaliculus of the main curl of the cochlea. 15 Jagged recess. 17 Styloid foramen. 18 Mastoid process. 19 Groove of the occipital artery. 20 Tenderloin of the mastoid.

Auditory or Eustachian tube is the front part of the middle ear, connects the tympanic cavity with the nasopharynx and serves to equalize air pressure, i.e. for physiological ventilation. Fig 12. Auditory tube.

The auditory tube is a continuation of the anteroposterior part of the tympanic cavity. The length of the auditory tube is about 37 mm. Immediately after the tympanic cavity, the auditory tube goes into the bony canal of the temporal bone pyramid, heading towards the center, down and anteriorly, repeating the direction of the temporal bone pyramid.

After leaving the pyramid of the temporal bone, the auditory tube has cartilaginous walls. A small bend is formed between the bony and cartilaginous walls of the auditory tube, in the form of a narrow isthmus, the diameter of which is 1.5 mm, while the diameter of its open opening in the tympanic cavity is 3 - 6 mm. A similar structure on one side protects the tympanic cavity from ascending infectionon the other hand can become a stubborn source of inflammation.

The cartilaginous part of the auditory tube has an end hole at the elevation of the side wall of the nasopharynx, it is 1 - 2.5 cm below the bone, tympanic opening of the auditory tube, which makes it difficult for the infection to climb into the tympanic cavity. Around the opening of the auditory tube are small lymphoid tonsilsprotecting the auditory tube from infection. The nasopharyngeal opening of the auditory tube is normally closed and opens only when swallowing, yawning, screaming, sneezing. This reflex opening of the auditory tube is caused by the contraction of the muscles of the soft palate, which are associated with the muscles of the cartilaginous part of the auditory tube. Swallowing movements should be made to induce the flow of air into the auditory tube and into the tympanic cavity during flight, especially during takeoff and landing.

In a newborn, the auditory tube is wider, shorter, and straighter, 19 mm long, the nasopharyngeal opening of which is almost at the level, or just below the tympanic opening of the auditory tube, which contributes to the penetration of infection into the tympanic cavity. In addition, the auditory tube in childhood there is no bend and isthmus, its opening is often open, which also contributes to the penetration of infection into the tympanic cavity. This is what contributes frequent inflammation middle ear in children. Figure: 13. Schematic relationship of the external auditory canal, tympanic cavity and auditory tube in a newborn and an adult. According to M. Ya. Kozlov and A.L. Levin.

The auditory tube is lined from the inside with a cylindrical epithelium, the movement of the cilia is directed towards the nasopharyngeal opening, which contributes to the evacuation of discharge from the tympanic cavity, and prevents the spread of infection into the auditory tube, that is, it performs a protective function.

The posterior wall of the tympanic cavity communicates with the cave and cells using a bone passage mastoid, also filled with air coming from the nasopharynx. The mastoid process consists of one large bony cavity, cavern, or antrum, and small bony cells. The size of the cells of the mastoid process is individual, but the antrum or cave is always present and communicates with the tympanic cavity. The antrum and cells, as well as the tympanic cavity, are filled with air that enters here from the nasopharynx, through the auditory tube immediately after the birth of the child, a process called pneumatization.

Ventilation of the cells of the mastoid process through the nasal cavity, auditory tube, tympanic cavity is an important condition for the healthy state of the middle ear, and impaired nasal breathing as a result of a runny nose, curvature of the nasal septum often causes or contributes to middle ear disease.

In a newborn, the mastoid process is very small, and is represented by a tubercle consisting of one cave, and as it grows, the mastoid process stretches out, acquires the shape of a nipple due to the movement of the neck muscles attached to it, and in addition to the cave, cells filled with air appear in it. By the age of 8 - 12, the process of pneumatization of the mastoid process ends, when, along with the antrum, air cells are formed in it.

The air cavities of the mastoid process, as well as other air cavities of the skull, contribute to giving a certain timbre to the voice, due to the air that is reflected from its walls.

Various external and internal negative factors affect the structure of the mastoid process. In children who have suffered inflammation of the mastoid process, or have a long-term chronic process in the tympanic cavity, the tissue of the mastoid process becomes very compact, sclerotic, and contains almost no air cavities.

Bone the mastoid process can have a spongy structure, that is, like a sponge, it consists of many very small cells, which is associated with a violation of nasal breathing, with the manifestation of rickets. The third type of structure of the mastoid process, pneumatic, is characterized by large cells filled with air, but this does not exclude the possibility of inflammation.

On the border of the tympanic cavity and the mastoid process there is bony canal of the facial nerveand above the canal lies a small cone for attaching the stapes muscle. The formation of a bony sheath around the facial nerve occurs at 12 to 18 months of age. Damage to the bony canal of the facial nerve with inflammation of the middle ear occurs in the chronic course of otitis media.

B arabic cavity at healthy person always contains air, only in newborns it is filled with embryonic tissue, which dissolves by 6 months, which, among other things, explains the hearing loss during this period.

The auditory ossicles are located mainly in the above the tympanic space, on top is the anterior surface of the pyramid.

Only outer process and hammer handle are woven into the fibrous layer of the tympanic membrane, giving it a peculiar appearance from the outside. Figure: 10. Auditory bones.

Three small auditory ossicles,connected and resembled in shape hammer, incus and stirrup. FROMrat seeds from with the help of ligaments, they are suspended from the bony walls of the tympanic cavity, and the tympanic membrane is connected with the oval window of the vestibule of the inner ear, due to which the sound wave from the eardrum propagates only to the region of the oval window of the vestibule of the inner ear.

The handle of the malleus passes into the isthmus and then into the head of the malleus and tightly adjoins the body of the incus, forming a tight articulation, due to which these two bones move as a whole. Anvil - the largest auditory bone, in addition to the body, has two scion: short with the help of a ligament it is connected to the back wall of the tympanic cavity, are longthe th process is directed downward, parallel to the handle of the malleus, its length is about 7 mm. The end of the long process bends inward and connects to the head of the stapes, forming a true, spherical joint, thanks to which the base of the stapes can rotate. Base of stirrup located between the two legs of the stapes extending from the head of the stapes, it is inserted into the oval window of the vestibule of the inner ear, covered with cartilage and secured with an annular ligament. Ossification of this ligament, which occurs with a disease called otosclerosis, disrupts the movement of the stirrup base and causes

The ratio of the stapes surface to the tympanic membrane is 1:22, which increases the pressure of sound waves on the membrane of the oval window by the same amount. This mechanism for increasing the sound pressure makes it possible to transmit even weak sound waves, especially low ones.

progressive hearing loss.

The inner surface of the tympanic cavity is lined with mucous membrane, which passes to the auditory ossicles located in the tympanic cavity and covers them.

The tympanic cavity is conventionally divided into three parts, which is due to a course of different severity inflammatory process in them. The upper part of the tympanic cavity is located above the tympanic membrane and is called over the drum space, attic,or epitympanum (epic - top, tympanum - air cavity). Epitympanum contains most auditory ossicles, inflammation of this part of the tympanic cavity is called epitympanite, proceeds for a long time and with complications.

The middle part of the tympanic cavity is called mesotympanum (mezzo - middle, tympanum - air cavity) corresponds to the stretched part of the tympanic membrane, its inflammation proceeds more benign.

Bottom part tympanic cavity - hypotympanum(hypo - smaller) is located below the attachment of the tympanic membrane, and becomes inflamed with inflammation of the auditory tube.

Hammer head and incus , constituting the largest mass of the auditory ossicles, are located in upper divisions tympanic cavity above the tympanic membrane, in the epitympanum. In the inflammatory process in this part of the tympanic cavity, which is located directly under the anterior wall of the pyramid, the head of the malleus and the incus often undergo carious changes, which causes a malignant course of the inflammatory process with its possible penetration into the middle cranial fossa.

The middle part of the tympanic cavity (mesotympanum) contains a smaller mass of the auditory ossicles, and its inflammation does not give serious complications.

The lower part of the tympanic cavity (hypotympanum), the front wall passes into the auditory tube, the inflammation of which leads to a catarrh of the middle ear, or otherwise tubo-otitis.

The auditory bones are suspended from the walls of the tympanic cavity not only by ligaments, but also by two muscles: stapes muscle and muscle straining the eardrum.

Stapes muscleshort, 6 mm long, it departs from the posterior wall of the tympanic cavity, at the border with the mastoid process, joins the head of the stirrup. Set in motion a branch of the facial nerve (drum string),which adjusts the degree of rotation of the stapes base depending on the sound intensity, that is, it performs an accommodative function. With an excessively strong sound wave, the base of the stapes rotates around its axis due to the presence of a spherical joint in the head of the stapes, and does not create pressure on the oval window, that is, it delays the passage of the auditory wave.

Muscle straining the tympanic membrane dline 25 mm. It is located above the bony canal of the auditory tube, in a special, bone cavity, and is directed from front to back, then bends at a right angle, crosses the tympanic cavity and is attached to the apex of the hammer handle. The muscle has the ability to change the degree of tension of the tympanic membrane and the auditory ossicles when conducting sounds of different heights and intensities, that is, it has an adaptive, accommodative function to change the sensitivity of the tympanic membrane, depending on the characteristics of the incoming sound wave... Set in motion the mandibular branch of the trigeminal nerve,which conducts both sensory impulses and motor impulses, and therefore is able to regulate the degree of tension of the tympanic membrane. Tympanic membrane tension. Fig.11. Muscle straining the eardrum

The innervation of the mucous membrane of the tympanic cavity is carried out tympanic nerve, a branch of the glossopharyngeal nervewhich connects to branches of the facial and trigeminal nerves ... The tympanic nerve departs from the lower node of the glossopharyngeal nerve, and gives branches to the mucous membrane of the tympanic membrane, to the cells of the mastoid process, the tubal branch to the mucous membrane of the auditory tube, as well as to the oval and round windows of the inner ear.