The ear is a paired organ that performs the function of perceiving sounds, and also controls balance and provides orientation in space. It is located in the temporal region of the skull and has an outlet in the form of the external auricles.
The structure of the ear includes:
- outer;
- average;
- internal department.
The interaction of all departments contributes to the transmission of sound waves, converted into a neural impulse and entering the human brain. The anatomy of the ear, analysis of each of the departments, makes it possible to describe a complete picture of the structure of the auditory organs.
This part of the overall auditory system is the pinna and auditory canal. The shell, in turn, consists of adipose tissue and skin; its functionality is determined by the reception of sound waves and subsequent transmission to hearing aid. This part of the ear is easily deformed, which is why it is necessary to avoid any rough physical impacts as much as possible.
Sound transmission occurs with some distortion, depending on the location of the sound source (horizontal or vertical), this helps to better navigate the environment. Next, behind the auricle, is the cartilage of the external ear canal (average size 25-30 mm).
Scheme of the structure of the outer section To remove dust and mud deposits, the structure has sweat and sebaceous glands. The connecting and intermediate link between the outer and middle ear is the eardrum. The principle of operation of the membrane is to capture sounds from the external auditory canal and convert them into vibrations of a certain frequency. The converted vibrations pass to the middle ear area.
Structure of the middle ear
The department consists of four parts - the eardrum itself and auditory ossicles located in its area (hammer, incus, stirrup). These components ensure the transmission of sound to the inner part of the hearing organs. The auditory ossicles form a complex chain that carries out the process of transmitting vibrations.
Scheme of the structure of the middle section The structure of the ear of the middle compartment also includes the Eustachian tube, which connects this section with the nasopharyngeal part. It is necessary to normalize the pressure difference inside and outside the membrane. If the balance is not maintained, the membrane may rupture.
Structure of the inner ear
The main component is the labyrinth - a complex structure in its shape and functions. The labyrinth consists of a temporal and osseous part. The structure is positioned in such a way that the temporal part is located inside the bone part.
Internal department diagram The inner part contains auditory organ called the cochlea, as well as the vestibular apparatus (responsible for general balance). The department in question has several more auxiliary parts:
- semicircular canals;
- utricle;
- stapes in the oval window;
- round window;
- scala tympani;
- spiral canal of the cochlea;
- pouch;
- staircase vestibule.
The cochlea is a spiral-type bony canal, divided into two equal parts by a septum. The partition, in turn, is divided by stairs connecting at the top. The main membrane is made up of tissues and fibers, each of which responds to a specific sound. The membrane includes an apparatus for the perception of sound - the organ of Corti.
Having examined the design of the hearing organs, we can conclude that all divisions are associated mainly with the sound-conducting and sound-receiving parts. For normal functioning ears, it is necessary to observe the rules of personal hygiene, avoid colds and injuries.
Eardrum is located at the end of the tympanic part of the pyramid of the temporal bone at an angle of 30° relative to the lower wall of the external auditory canal. In a newborn, the eardrum 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 pyramid of the temporal bone.
The tympanic part of the temporal bone.
The eardrum is translucent, very thin, about 0.1 mm, pearl-gray in color, has an almost round shape, since the vertical size of the eardrum is about 0.9 cm - 1 cm, horizontally - 0.8 - 0.9 cm ., the area of the eardrum is about 60 mm 2.
Top part eardrum relaxed, folded, because it consists of two layers: on the side of the external auditory canal it is covered with epidermis, and on the side of the tympanic cavity with epithelium. At the top, 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 eardrum, it is visible as a yellowish grain, with two folds extending from it. Folds are a conditional boundary separating the upper, relaxed part of the eardrum, which is only 10% of the area of the eardrum, from the lower, stretched part. Rice. 7 Left eardrum. Rice. 8. Right eardrum.
At the bottom, tense part of the two layers of the eardrum is added a layer consisting of connective tissue with circular and radial, elastic fibers, resembling a web in shape, and giving special strength to the stretched part of the eardrum.
The tense part of the eardrum is much larger than the relaxed part, making up more than 90% of the area of the eardrum, and with the help of fibrous fibers of the 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 eardrum is tightly fused with the handle of the malleus, which is visible in the form of a pale yellowish strip running from the outer process of the malleus to the center and slightly posteriorly.
For the right eardrum, 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 navel of the membrane. In this part, the eardrum is retracted into the tympanic cavity in the form of a cone, and the navel corresponds to the top of the cone.
Since the eardrum ruptures during inflammation - perforation, it is conventionally divided into four parts to indicate the location of the perforation. The division is carried out using 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 eardrum is divided into two quadrants: anterior - superior and anterior - inferior. Accordingly, the back half is on the back - upper and back - lower quadrants. Using this division, you can, if necessary, clarify the location of the rupture (perforation) of the eardrum.
Examining the 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, after first retracting the auricle to straighten the spiral bend of the external auditory canal. A light spot appears on the mirror surface of the eardrum, in the form of a triangle, the apex of which is located at the navel, and the base is on the anterior lower quadrant of the eardrum. This is the so-called light cone, which is always visible on a healthy eardrum and is absent in its pathology.
The tympanic membrane is pierced by endings tympanic nerve, which departs from inferior sensory ganglion 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 its 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 pyramid of the temporal bone and the central part of the middle ear, it is a narrow, bony gap filled with air, with a volume of about 1 - 2 cm 3, similar to a drum, or tambourine, placed on the edge, and inclined towards the external auditory canal.
Outer wall the tympanic cavity is eardrum, A inner wall The 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.
Upper bony wall of the tympanic cavity or roof It is at the same time the anterior 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 young children, at the junction of the pyramid and the scaly part of the temporal, there is a gap, which is subsequently filled with connective tissue. Such a close location of the tympanic cavity to the middle cranial fossa may be the cause of inflammatory lesions of the temporal lobe of the brain during chronic processes in the tympanic cavity. Fig.9 Bone walls of the tympanic cavity.
The lower bony wall of the tympanic cavity, being inferior wall of the pyramid of the temporal bone, borders the outer base of the skull, where the thickened jugular vein or bulb is located in a bony cavity jugular vein. Inflammation of the tympanic cavity, causing damage to bone tissue, penetrates the vascular wall of the jugular vein bulb and contributes to the formation of a blood clot. The resulting thrombus impedes the outflow of venous blood from the skull and is one of severe complications chronic inflammation of the middle ear
The lower wall of the pyramid of the temporal bone. 
1External auditory canal. 2 Styloid process. 3 Tympanic part of the pyramid of the temporal bone. 4 Mandibular fossa. 5 Recess of the pyramid 6 Zygomatic process. 7,8,9 Gap between the stony and scaly parts. 10 Hemicanal of the auditory tube and the tensor tympani muscle. 11 Inner hole sleepy channel. 12 External opening of the carotid canal. 13 Pyramid pit. 14 The opening of the canaliculus of the main helix of the cochlea. 15 Jugular recess. 17 Stylomastoid foramen. 18 Mastoid process. 19 Groove of the occipital artery. 20 Mastoid notch.
Auditory or Eustachian tube is the anterior 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. Eustachian tube.
The auditory tube is a continuation of the anterior inferior part of the tympanic cavity. The length of the auditory tube is about 37 mm. Immediately after the tympanic cavity, the auditory tube runs in the bony canal of the pyramid of the temporal bone, heading towards the center, down and anteriorly, repeating the direction of the pyramid of the temporal bone.
After exiting the pyramid of the temporal bone, the auditory tube has cartilaginous walls. A small bend is formed between the bone 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. Such a structure, on the one hand, protects the tympanic cavity from ascending infection, on the other hand, it can become a persistent source of inflammation.
The cartilaginous part of the auditory tube has an end opening at the elevation of the lateral wall of the nasopharynx; it is 1–2.5 cm below the bony, tympanic opening of the auditory tube, which makes it difficult for infection to ascend into the tympanic cavity. Around the opening of the auditory tube there are small lymphoid tonsils protecting the auditory tube from infection. The nasopharyngeal opening of the auditory tube is closed under normal conditions and opens only when swallowing, yawning, screaming, or sneezing. This reflex opening of the auditory tube is caused by muscle contraction soft palate, which are connected to the muscles of the cartilaginous part of the auditory tube. To cause air flow into the auditory tube and into the tympanic cavity during flight, especially during takeoff and landing, swallowing movements should be made.
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 facilitates the penetration of infection into the tympanic cavity. In addition, the auditory tube in childhood does not have a bend or isthmus; its opening is often open, which also facilitates the penetration of infection into the tympanic cavity. This is what contributes to frequent inflammation of the middle ear in children. Rice. 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 cylindrical epithelium, the movement of the cilia is directed towards the nasopharyngeal opening, which promotes 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.
Posterior wall of the tympanic cavity with the help of a bone passage it communicates with the cave and cells mastoid process, also filled with air coming from the nasopharynx. The mastoid process consists of one large bony cavity, a cave, or antrum, and small bony cells. The size of the mastoid cells varies individually, 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, which comes here from the nasopharynx through the auditory tube immediately after the birth of the child, a process called pneumatization.
Ventilation of the mastoid cells through the nasal cavity, auditory tube, and tympanic cavity is an important condition For healthy condition middle ear, and impaired nasal breathing as a result of a runny nose or deviated 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 elongates, takes on 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 years, 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 who 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.
The bone tissue of the mastoid process can have a spongy structure, that is, like a sponge, it can consist of many very small cells, which is associated with impaired nasal breathing and 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.
At the border of the tympanic cavity and the mastoid process there is bony canal of the facial nerve, and above the canal lies a small cone for the attachment of the stapes muscle. The formation of a bone sheath around the facial nerve occurs between 12 and 18 months of life. Damage to the bony canal of the facial nerve due to inflammation of the middle ear occurs when chronic course otitis media.
B arabic cavity at healthy person always contains air, only in newborns it is filled with embryonic tissue, which resolves by 6 months, which, among other things, explains the decrease in hearing during this period.
The auditory ossicles are located mainly in the supratympanic space, with the anterior surface of the pyramid located on top.
Only external process And hammer handle are woven into the fibrous layer of the eardrum, giving it a peculiar appearance from the outside. Rice. 10. Auditory ossicles.
Three little ones auditory ossicles, related to each other and resemble in shape hammer, anvil and stirrup. WITH ear ossicles With with the help of ligaments they are suspended from the bony walls of the tympanic cavity, and connect the eardrum with oval window vestibule of the inner ear, due to which the sound wave from the eardrum extends only to the area 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 is tightly adjacent to the body of the incus, forming a tight joint, due to which these two bones move as a single unit. Anvil- the largest auditory ossicle; in addition to the body, it has two process: short with the help of a ligament it is connected to the posterior wall of the tympanic cavity, length The th process is directed downwards, parallel to the handle of the malleus, its length is about 7 mm. The end of the long process curves inward and connects to the head of the stapes, forming a true, ball-and-socket joint that allows the base of the stapes to rotate. Stirrup base 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 by an annular ligament. Ossification of this ligament, which occurs in a disease called otosclerosis, disrupts the movement of the base of the stapes and causes
The ratio of the surface of the stapes 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 of increasing sound pressure allows even weak sound waves, especially low ones, to be transmitted.
progressive hearing loss. 
Inner surface of the tympanic cavity 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 the different severity of the inflammatory process in them. The upper part of the tympanic cavity is located above the eardrum and is called above the tympanic space, attic, or epitympanum(epic - apex, tympanum - air cavity). Epitympanum contains most auditory ossicles, inflammation of this part of the tympanic cavity is called epitympanitis, proceeds for a long time and with complications.
middle part the tympanic cavity is called mesotympanum(mezzo - middle, tympanum - air cavity) corresponds to the tense part of the eardrum, its inflammation is more benign.
The lower part of the tympanic cavity - hypotympanum(hypo - smaller) is located below the attachment of the eardrum, and becomes inflamed when the auditory tube becomes inflamed.
Head of the malleus and incus , components greatest mass auditory ossicles, located in upper sections tympanic cavity above the eardrum, in the epitympanum. During 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 poor-quality course of the inflammatory process with possible penetration into the middle cranial fossa.
The middle part of the tympanic cavity (mesotympanum) contains a smaller mass of auditory ossicles, and its inflammation does not cause serious complications.
The lower part of the tympanic cavity (hypotympanum), the anterior wall, passes into the auditory tube, inflammation of which leads to catarrh of the middle ear, or otherwise tubootitis.
The auditory ossicles are suspended from the walls of the tympanic cavity not only by ligaments, but also by two muscles: stapedius muscle and tensor tympani muscle.
Stapedius muscle short, its length is 6 mm, it extends from the posterior wall of the tympanic cavity, at its border with the mastoid process, and joins the head of the stapes. Set in motion branch of the facial nerve (corda tympani), which adapts the degree of rotation of the base of the stapes depending on the intensity of the sound, that is, it performs an accommodative function. When the sound wave is excessively strong, 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.
Tensor tympani muscle d line 25 mm. It is located above the bony canal of the auditory tube, in a special bony recess, and is directed from front to back, then bends at a right angle, crosses the tympanic cavity and is attached to the top of the malleus handle. The muscle has the ability to change the degree of tension of the eardrum and auditory ossicles when carrying out sounds of varying heights and intensities, that is, it has an adaptive, accommodative function to change the sensitivity of the eardrum depending on the characteristics of the incoming sound wave. Set in motion mandibular branch of the trigeminal nerve, which conducts both sensory impulses and motor impulses, and is therefore able to regulate the degree of tension of the eardrum. Eardrum tension. Fig. 11. Tensor tympani muscle
Innervation of the mucous membrane of the tympanic cavity is carried out tympanic nerve, branch of the glossopharyngeal nerve, which connects with branches of the facial and trigeminal nerves. The tympanic nerve departs from the lower ganglion of the glossopharyngeal nerve, and gives branches to the mucous membrane of the tympanic membrane, to the cells of the mastoid process, a tubal branch to the mucous membrane of the auditory tube, as well as to the oval and round windows of the inner ear.
Human organism - a complex system. It’s not for nothing that medical schools spend a lot of time studying anatomy. The structure of the auditory system is one of the most complex topics. Therefore, some students are confused when they hear the question “What is the tympanic cavity?” in the exam. It will be interesting to know about this for people who do not have a medical education. Let's look at this topic later in the article.
Anatomy of the middle ear
The human auditory system consists of several parts:
- outer ear;
- middle ear;
- inner ear.
Each site has a special structure. Thus, the middle ear performs a sound-conducting function. Located in the temporal bone. Includes three air cavities.
The nasopharynx and tympanic cavity are connected using the Posterior - air cells of the mastoid process, including the largest, the mastoid cave.
The tympanic cavity of the middle ear is shaped like a parallelepiped and has six walls. This cavity is located in the thickness of the pyramid of the temporal bone. The upper wall is formed by a thin bone plate, its function is to separate from the skull, and its thickness reaches a maximum of 6 mm. Small cells can be found on it. The plate separates the middle ear cavity from the temporal lobe of the brain. Below, the tympanic cavity is adjacent to the bulb of the jugular vein.
The tympanic cavity can also be affected due to inflammation in the mastoid cave. This disease is called mastoiditis. Most often, the infection enters this area from the lymphatic or circulatory system, since the vessels pass densely in this place. Often inflammation occurs against the background of a sluggish infection, such as pyelonephritis. In this case, the bacteria spread through the bloodstream and infect the mastoid cells.
The tympanic cavity is a part of the middle ear that includes important bones: the stirrup, malleus and incus. Important Feature This area is the conversion of a sound wave into a mechanical one and its delivery to the recipes inside the cochlea. That's why inflammatory processes in this place there is a risk of temporary or permanent hearing loss.
The human auditory sensory system perceives and distinguishes a huge range of sounds. Their diversity and richness serves for us both as a source of information about current events in the surrounding reality, and important factor, affecting the emotional and mental state of our body. In this article we will look at the anatomy of the human ear, as well as the features of its functioning. peripheral part auditory analyzer.
Mechanism for distinguishing sound vibrations
Scientists have found that the perception of sound, which is essentially air vibrations in the auditory analyzer, is transformed into the process of excitation. Responsible for the sensation of sound stimuli in the auditory analyzer is its peripheral part, which contains receptors and is part of the ear. It perceives vibration amplitude, called sound pressure, in the range from 16 Hz to 20 kHz. In our body, the auditory analyzer also plays such an important role as participation in the work of the system responsible for the development of articulate speech and the entire psycho-emotional sphere. First, let's get acquainted with the general plan of the structure of the hearing organ.
Sections of the peripheral part of the auditory analyzer
The anatomy of the ear distinguishes three structures called the outer, middle and inner ear. Each of them performs specific functions, not only interconnected, but also collectively carrying out the processes of receiving sound signals and converting them into nerve impulses. They are transmitted along the auditory nerves to the temporal lobe of the cerebral cortex, where sound waves are transformed into the form of various sounds: music, birdsong, noise sea surf. In the process of phylogenesis of the biological species “Homo sapiens,” the organ of hearing played a vital role, as it ensured the manifestation of such a phenomenon as human speech. The sections of the hearing organ were formed during human embryonic development from the outer germ layer - the ectoderm.
Outer ear
This part of the peripheral section captures and directs air vibrations to the eardrum. The anatomy of the external ear is represented by the cartilaginous concha and the external ear canal. What does it look like? The external shape of the auricle has characteristic curves - curls, and is very different in different people. One of them may contain Darwin's tubercle. It is considered a vestigial organ, and is homologous in origin to the pointed upper edge of the ear of mammals, especially primates. The lower part is called the lobe and is connective tissue covered with skin.
The auditory canal is the structure of the outer ear
Further. The auditory canal is a tube consisting of cartilage and partly bone tissue. It is covered with epithelium containing modified sweat glands that secrete sulfur, which moisturizes and disinfects the passage cavity. The muscles of the auricle in most people are atrophied, unlike mammals, whose ears actively respond to external sound stimuli. Pathologies of violations of the anatomy of the ear structure are recorded in early period development of the branchial arches of the human embryo and can take the form of splitting of the lobe, narrowing of the external auditory canal, or agenesis - the complete absence of the auricle.
Middle ear cavity
The auditory canal ends with an elastic film that separates the outer ear from its middle part. This is the eardrum. It receives sound waves and begins to vibrate, which causes similar movements of the auditory ossicles - the hammer, incus and stapes, located in the middle ear, deep in the temporal bone. The hammer is attached to the eardrum with its handle, and its head is connected to the incus. It, in turn, with its long end closes with the stapes, and it is attached to the window of the vestibule, behind which the inner ear is located. Everything is very simple. The anatomy of the ears has revealed that a muscle is attached to the long process of the malleus, which reduces the tension of the eardrum. And the so-called “antagonist” is attached to the short part of this auditory ossicle. A special muscle.
Eustachian tube
The middle ear is connected to the pharynx through a canal named after the scientist who described its structure, Bartolomeo Eustachio. The pipe serves as a device that equalizes the atmospheric air pressure on the eardrum on both sides: from the external auditory canal and the middle ear cavity. This is necessary so that vibrations of the eardrum are transmitted without distortion to the fluid of the membranous labyrinth of the inner ear. The Eustachian tube is heterogeneous in its histological structure. The anatomy of the ears has revealed that it contains more than just a bone part. Also cartilaginous. Descending down from the middle ear cavity, the tube ends with the pharyngeal opening, located on the lateral surface of the nasopharynx. During swallowing, the muscle fibrils attached to the cartilaginous part of the tube contract, its lumen expands, and a portion of air enters the tympanic cavity. The pressure on the membrane at this moment becomes equal on both sides. Around the pharyngeal opening there is an area of lymphoid tissue that forms nodes. It is called Gerlach's tonsil and is part of the immune system.
Features of the anatomy of the inner ear
This part of the peripheral auditory sensory system located deep in the temporal bone. It consists of semicircular canals related to the organ of balance and the bony labyrinth. The last structure contains the cochlea, inside which is the organ of Corti, which is a sound-receiving system. Along the spiral, the cochlea is divided by a thin vestibular plate and a denser basilar membrane. Both membranes divide the cochlea into canals: lower, middle and upper. At its wide base, the upper canal begins with an oval window, and the lower one is closed with a round window. Both of them are filled with liquid contents - perilymph. It is considered a modified cerebrospinal fluid - a substance that fills the spinal canal. Endolymph is another fluid that fills the canals of the cochlea and accumulates in the cavity where the nerve endings of the organ of balance are located. Let's continue to study the anatomy of the ears and consider those parts of the auditory analyzer that are responsible for transcoding sound vibrations into the process of excitation.
Significance of the organ of Corti
Inside the cochlea there is a membranous wall called the basilar membrane, on which there is a collection of two types of cells. Some perform the function of support, others are sensory - hair-like. They perceive vibrations of the perilymph, convert them into nerve impulses and transmit them further to the sensory fibers of the vestibulocochlear (auditory) nerve. Next, the excitation reaches the cortical hearing center, located in temporal lobe brain. It distinguishes sound signals. The clinical anatomy of the ear confirms the fact that what we hear with both ears is important in determining the direction of sound. If sound vibrations reach them simultaneously, a person perceives sound from the front and back. And if the waves arrive in one ear earlier than in the other, then perception occurs on the right or left.
Theories of sound perception
At the moment, there is no consensus on how exactly the system functions, analyzing sound vibrations and translating them into the form of sound images. The anatomy of the human ear structure highlights the following scientific concepts. For example, Helmholtz's resonance theory states that the main membrane of the cochlea functions as a resonator and is capable of decomposing complex vibrations into simpler components because its width is unequal at the apex and base. Therefore, when sounds appear, resonance occurs, as in a string instrument - a harp or a piano.
Another theory explains the process of sound appearance by the fact that a traveling wave appears in the cochlear fluid as a response to vibrations of the endolymph. The vibrating fibers of the main membrane resonate with a specific vibration frequency, and nerve impulses arise in the hair cells. They travel along the auditory nerves to the temporal part of the cerebral cortex, where the final analysis of sounds occurs. Everything is extremely simple. Both of these theories of sound perception are based on knowledge of the anatomy of the human ear.
The ear contains two sensory organs with different functions (hearing and balance), which, however, anatomically form a single whole.
The ear is located in the petrous part of the temporal bone (the petrous part is sometimes called simply petrous bone) or the so-called pyramid, and consists of the cochlea and the vestibular apparatus (labyrinth), which includes two fluid-filled sacs and three semicircular canals, also filled with fluid. The organ of hearing, unlike the vestibular apparatus, has auxiliary structures that ensure the conduction of sound waves: the outer ear and the middle ear.
The outer ear includes Auricle, external auditory canal about 3 cm long and eardrum.
The auricle consists mainly of elastic cartilage, which extends into the external opening of the external auditory canal.
In its cartilaginous part there are numerous ceruminous glands that secrete ear wax. The eardrum stretches across the inner end of the bony canal and is the boundary of the middle ear.
The middle ear contains tympanic cavity, lined with mucous membrane and containing auditory ossicles - hammer, anvil And stapes, eustachian tube, which is a continuation of the tympanic cavity forward into the pharynx, as well as numerous cavities in the mastoid process of the temporal bone, lined with mucous membrane.
The eardrum is almost round, 1 cm in diameter; it forms the outer wall of the tympanic cavity. The eardrum consists of three layers.
The predominantly rigid connective tissue base of the eardrum is tension-free only in a small area near its upper end. Its inner surface is lined with mucous membrane, and its outer surface is lined with skin.
The long handle of the malleus, attached to the eardrum, causes it to curve inward like a funnel. The auditory ossicles, together with the eardrum, make up the sound-conducting apparatus.
Hammer, anvil And stapes form a continuous chain connecting eardrum And oval window of the vestibule, into which the base of the stapes is embedded.
The auditory ossicles conduct vibrations generated by sound waves in the eardrum into the oval window of the inner ear.
The oval window, together with the first turn of the cochlea, forms the internal bony border of the tympanic cavity. The base of the stapes in the oval window transmits vibrations to the fluid that fills the inner ear.
The malleus and stirrup are additionally fixed by two muscles, on which the intensity of sound transmission depends.
The inner ear is surrounded by a hard bone capsule and consists of systems of ducts and cavities (bone labyrinth) filled with perilymph.
Inside the bony labyrinth there is a membranous labyrinth filled with endolymph. Perilymph and endolymph differ primarily in their sodium and potassium content.
The membranous labyrinth contains the organs of hearing and balance.
Bone spiral (cochlea) The inner ear, about 3 cm long, forms a canal, which in humans makes approximately 2.5 turns around the bony central rod - the columella.
A cross section of the cochlea shows three separate cavities: in the middle is the cochlear canal. The cochlear canal is also often called the middle scala; underneath it lies the scala tympani and vestibular scala, which are connected at the apex of the cochlea through an opening called the helicotrema.
These cavities are filled with perilymph and end with the round window of the cochlea and the oval window of the vestibule, respectively. The cochlear duct is filled with endolymph and is separated from the scala tympani by the main (basilar) membrane, and from the scala vestibular by the Reissner (vestibular) membrane.
Organ of Corti (spiral organ) located on the main membrane.
It contains about 15,000 auditory sensory cells arranged in rows (inner and outer hair cells), as well as many supporting cells.
The hairs of the sensory cells are attached to the gelatinous integumentary (tentorial) membrane located above them.
Hair cells form synapses with neurons, the cell bodies of which lie in the spiral ganglion of the cochlea in the central core.
From here, the central branches of their axons go as part of the cochlear and vestibular nerves of cranial nerve VIII (vestibular-cochlear nerve) into the brain stem.
There, the axons of the cochlear nerve end in the cochlear nuclei, and the axons of the vestibular nerve end in the vestibular nuclei.
On its way to the auditory region in the anterior transverse gyrus of the temporal lobe, the auditory pathway passes through several synaptic switches, including in the medial geniculate body of the diencephalon.
Source: http://www.sportmassag.ru/1/page6279.html
What is the middle ear and how to treat diseases associated with it?
The middle ear is part of the human auditory system. It is a small space between two other parts of the organ: the external auditory canal and the labyrinth (inner ear).
Structure of the middle ear
The middle ear contains:
- tympanic cavity;
- auditory (Eustachian) tube;
- a cave surrounded by mastoid cells.
Let's take a closer look at the structure of the middle ear. Each cavity is filled with air. The tympanic cavity of the middle ear is shaped like a tambourine, standing on its edge and strongly inclined towards the external auditory canal. It is small in volume - only about 1 cm³.
The middle ear contains three auditory ossicles: the malleus, the incus and the stapes. They got their name from their appearance.
The auditory ossicles are located directly behind the eardrum. They are connected by a pair of real joints of limited mobility.
They are also strengthened by a number of individual ligaments, so they represent a more or less movable chain.
However, in the direction from the malleus to the stapes, the mobility of the auditory ossicles gradually decreases. In this way, the spiral organ of the inner ear is protected from shocks and negative impact loud sounds.
Between the tympanic cavity and the nasopharynx is the Eustachian tube, through which the pressure in the middle ear is equalized. If it does not correspond to the atmospheric one, the ears become blocked and the person reflexively begins to yawn.
Functions of the middle ear
The function of the middle ear is sound conduction. Wave-like vibrations of air create sound waves that vibrate the eardrum and auditory ossicles. These vibrations, slightly modified, are transmitted to the inner ear.
The structure of the middle ear allows it to perform the following functions:
- maintaining the eardrum and the chain of auditory ossicles in good shape;
- adaptation of the acoustic apparatus to sounds of varying strength and pitch;
- protection from harsh sounds.
When pressure in the middle ear increases, the amplitude of vibration of the auditory ossicles decreases.
As a result, the sensitivity of the acoustic device decreases. About 10 ms after the appearance of a sound of more than 40 dB, two muscles begin to reflexively contract.
One of them, attached to the handle of the hammer, increases the tension of the eardrum and reduces the amplitude of its vibrations. The other limits the vibrations of the stapes.
Thanks to this, the human auditory system adapts to intense sounds that can harm the body.
Middle ear diseases
Middle ear diseases include a number of pathological conditions. All of them are called otitis. The diseases are equally common among both adults and children.
Often, otitis media leads to hearing loss, which reduces social activity and professional suitability. Advanced cases threaten intracranial complications and even death. That is why it is so important to diagnose the disease in time and begin treatment.
Otitis is divided into acute and chronic. Moreover acute form easily becomes chronic. There are also serous and purulent otitis media.
These diseases are rarely primary and almost always develop with inflammation of the upper respiratory tract. When you have a cold, bacteria and viruses travel from the nasopharynx into the auditory tube, and then into the middle ear.
Thus, provoking factors are diseases that make nasal ventilation difficult:
- adenoids;
- nasal polyps;
- abnormal structure of the nasal septum;
- hypertrophy of the nasal concha;
- sinusitis.
The prevalence of inflammation and the possibility of full recovery after the disease depend on the stage of damage to the auditory tube, the virulence of viruses and bacteria, and the resistance of the patient’s body.
Symptoms of otitis media
Symptoms of otitis consist of the following signs:
- pain in the ear and surrounding tissues.
- headache, in rare cases - vomiting;
- hearing impairment;
- feverish conditions;
- noise in ears;
- feeling foreign body in the ear cavity.
When the first symptoms appear, you should consult a doctor, since untimely or incorrect treatment is fraught with complications.
For a patient with acute otitis media, the doctor will first of all prescribe bed rest. Medicines prescribed include antibiotics, sulfonamides, vasoconstrictor drops for the nose, compresses and heating pads for the ear. Ear drops relieve pain well.
An inflamed human ear must be protected from drafts. It is useful to warm it up with blue light or a Sollux lamp. Procedures can be performed at home, but only as a supplement to medical prescriptions.
In the case of otitis media, self-medication is strictly contraindicated. With inflammation complicated by the formation of pus, the infection often penetrates into the cranial cavity.
In this case, the risk of developing meningitis, abscesses of the temporal lobe of the brain and cerebellum, sinus thrombosis and even sepsis (blood poisoning) increases.
Diagnosis and treatment
Put accurate diagnosis Otitis can only be diagnosed by a qualified otolaryngologist. First, the doctor examines the patient's ear using an otoscope.
Very often, the signs of the disease are unclear or only partially present, so additional time is required to confirm the diagnosis.
In addition, examination of the ear cavity may be difficult due to the accumulation of earwax. To continue diagnostics, it must be removed.
A comprehensive examination consists of determining the following signs:
- is there inflammation in the tympanic cavity;
- are there any complications (pus, hearing loss, thinning of the eardrums);
- what bacteria or virus are the causative agents, their resistance to antibiotics;
- what is the stage of the disease and is there a need for drug therapy.
When treating otitis, the patient is usually at home; round-the-clock medical supervision is not required. Hospitalization is carried out only if there is a suspicion of severe purulent complications, for example, meningitis.
Drug therapy consists of antibiotics, antipyretics, painkillers (individually or all in combination). Improvement in the patient's well-being, as a rule, occurs within 1 - 2 days. Otherwise, it is necessary to urgently appear for examination by a doctor.
Prevention of otitis media
Prevention of otitis media consists of maintaining careful personal hygiene, timely treatment diseases of the nose, pharynx, combating chronic infections.
For the health of the middle ear, it is necessary to treat inflammation of the outer ear in a timely manner. If at work a person is in contact with chemicals, personal protective equipment must be used.
To exclude acoustic trauma, it is necessary to undergo annual medical examinations. If pathologies are detected, doctors advise changing jobs. In production, it is necessary to use earplugs, swabs, helmets and other protective equipment. The room must be soundproofed.
The structure of the tympanic cavity implies its sensitivity to changes in atmospheric pressure, and there is a risk of barotrauma.
Therefore, it is necessary to take precautions when jumping with a parachute, flying in an airplane, or diving to depths.
In case of injury, you should not wash your ear yourself, as there is a high risk of infection of the tympanic cavity.
Prevention of vibration injuries in the ear cavity includes vibration isolation, vibration absorption and vibration damping.
Source: https://vashlor.ru/anatomiya/srednee-uho.html
The human ear has a very complex anatomical structure that allows it to capture sound waves, determine the direction of the sound source and correctly identify it.
It consists of three main sections: the outer, middle and inner ear. Each of which has strictly defined functions and a special structure.
The human middle ear primarily performs the conversion of sound waves into nerve impulses. This is its main, but not the only function.
The middle ear begins just behind the eardrum, which is located at the end of the ear canal and separates it from the outer ear. The middle ear consists of three main elements:
- tympanic cavity;
- mastoid processes;
- auditory tube
The eardrum is a small piece of thin connective tissue that is directly involved in converting sound waves received by the outer ear.
The tympanic cavity of the middle ear is located in the recess of the temporal bone. Inside it, in close proximity, are the three smallest bones of the human skeleton: the malleus, stirrup and incus.
Acoustic waves cause the eardrum to vibrate, and these vibrations are transmitted to the bones. And the stirrup sends a signal through the oval window to the fluid that fills the inner ear - perilymph.
Interestingly, the design of the auditory ossicles allows not only transmission, but also significantly amplification of sound.
The surface of the stapes is an order of magnitude smaller than the area of the eardrum, which means it hits the oval window much stronger, giving a person the opportunity to hear even very quiet sounds.
Protective functions of the middle ear
The functions of the middle ear are not limited to sound conduction. It is also a reliable protective barrier that protects the delicate inner ear from:
- ingress of moisture, dust and dirt particles;
- penetration and reproduction of pathogenic microorganisms;
- too intense exposure to sound waves;
- sudden changes in atmospheric pressure;
- mechanical impact.
The middle ear cavity is filled with air and connects to the nasopharynx via the Eustachian tube.
Under normal conditions, there is equal air pressure on both sides of the eardrum.
But if the atmospheric pressure changes sharply in any direction, then this stretches the eardrum and can lead to its rupture.
This phenomenon is called barotrauma. The same thing happens when you suddenly dive to great depths. To prevent barotrauma, the dive should be done slowly. And when taking off or landing a plane, open your mouth slightly or make frequent swallowing movements.
The anatomy of the middle ear allows for partial compensation of loud sounds. It houses two very small muscles, one of which controls the tension of the eardrum, and the other controls the amplitude of vibration of the stapes.
The protective mechanism inherent in nature provides a reflexive contraction of these muscles when too much loud sounds. The movement of the stapes is limited and ear sensitivity is temporarily reduced. It takes about 10 ms to trigger.
Therefore, during explosions, gunshots and other rapid sounds, it does not have time to compensate for the noise.
Middle ear diseases
The structure of the middle ear is such that when it is diseased, the normal conductivity of sound is primarily affected and the threshold of hearing sensitivity is sharply reduced. Inner ear diseases are most often caused by injury, hypothermia, or exposure to pathogenic microorganisms.
Among the most common diseases of the middle ear, doctors note:
- acute and chronic otitis;
- barotrauma;
- mechanical injuries;
- congenital pathologies;
- hearing loss 1-4 degrees.
Especially dangerous is purulent otitis, which, in the absence of proper treatment may lead to inflammation meninges(meningitis) and even general blood poisoning (sepsis).
Pus accumulates behind the eardrum and presses on it, causing severe pain.
Sometimes there is partial perforation, and in some cases there is a complete rupture, which can lead to partial or complete loss hearing
Unfortunately, the structure of the middle ear is such that diseases appear already at the stage when the inflammatory process has developed.
The main symptoms of disease of this organ are: sharp shooting pain, increased body temperature, often redness of the tragus, headache, and periodic dizziness.
With otitis media, pus or yellowish exudate with an unpleasant odor may be released from the ear. If these symptoms appear, you should immediately consult a doctor. Delay and improper treatment can have very serious consequences.
Anna Alexandrova
Source: https://lorcabinet.com/anatomiya-uha/srednee.html
Includes a mucous membrane-lined and air-filled tympanic cavity (about 1 cubic meter in volume).
cm) and the auditory (Eustachian) tube.
The middle ear cavity communicates with the mastoid cave and through it with the mastoid cells located in the thickness of the mastoid process.
Tympanic cavity located in the thickness of the pyramid of the temporal bone, between the external auditory canal laterally and the bony labyrinth of the inner ear medially. The tympanic cavity, in which 6 walls are distinguished, is compared in shape to a tambourine placed on its edge and tilted outward.
- Upper tire wall formed by a thin plate of bone substance separating the tympanic cavity from the cranial cavity.
- Inferior jugular wall corresponds to the lower wall of the pyramid in the place where the jugular fossa is located.
- Medial labyrinthine wall complexly arranged, separates the tympanic cavity from the bony labyrinth of the inner ear. On this wall there is a promontory protruding towards the tympanic cavity. Above the promontory and somewhat posteriorly there is the oval window of the vestibule, leading into the vestibule of the bony labyrinth; it is covered by the base of the stirrup.
- Slightly above the oval window and behind it there is a transverse protrusion of the facial canal ( walls of the facial nerve canal). Behind and below the promontory is the window of the cochlea, closed by the secondary tympanic membrane, which separates the tympanic cavity from the scala tympani.
- Posterior mastoid wall, in the lower part it has a pyramidal eminence, within which the stapedius muscle begins. In the upper part of the posterior wall, the tympanic cavity continues into the mastoid cave, into which the mastoid cells of the process of the same name also open.
- Anterior carotid wall, in its lower part it separates the tympanic cavity from the carotid canal, in which the internal carotid artery passes. In the upper part of the wall there is an opening of the auditory tube, which connects the tympanic cavity with the nasopharynx.
- Lateral membranous wall formed by the eardrum and the surrounding parts of the temporal bone.
In the tympanic cavity there are three auditory ossicles covered with mucous membrane, as well as ligaments and muscles.
Auditory ossicles miniature in size, connecting with each other, they form a chain that continues from the eardrum to the end of the vestibule, which opens into the inner ear.
In accordance with their shape, the bones are named: hammer, anvil, stirrup. The malleus has a rounded head, which turns into a long handle of the malleus with two processes: lateral and anterior.
The incus consists of a body, with an articular fossa for articulation with the head of the malleus, and two legs: one short leg, the other long, with a thickening at the end. This thickening is a lenticular process for connection with the head of the stapes.
The stapes has a head, two legs - anterior and posterior, connected by the base of the stirrup, inserted into the window of the vestibule.
The hammer with its handle is fused with the eardrum along its entire length so that the end of the handle corresponds to the navel on outside membranes.
The head of the malleus, with the help of a joint, connects to the body of the incus and forms the incus-malleus joint, and the incus, in turn, with its lenticular process connects to the head of the stapes, forming the incus-stapedius joint. The joints are strengthened by miniature ligaments.
With the help of a chain movable in the joints, consisting of three auditory ossicles, vibrations of the tympanic membrane, resulting from the influence of a sound wave on it, are transmitted to the window of the vestibule, in which the base of the stapes is movably secured using the annular ligament of the stapes. Two muscles attached to the auditory ossicles regulate the movements of the ossicles and protect them from excessive vibrations during strong sounds. The muscle that tensor the tympanic membrane lies in the hemicanal of the muscular-tubal canal of the same name, and its thin and long tendon is attached to the initial part of the handle of the malleus. This muscle, pulling the handle of the hammer, strains the eardrum. The stapedius muscle, starting in the pyramidal eminence, is attached by a thin tendon to the posterior leg of the stapes, near its head. When the stapedius muscle contracts, the pressure of the base of the stapes inserted into the window of the vestibule is weakened.
Auditory (Eustachian) tube, on average 3-5 mm long, 2 mm wide, serves to bring air from the pharynx into the tympanic cavity and maintain pressure in the cavity equal to the external one, which is important for normal operation sound-conducting apparatus (tympanic membrane and auditory ossicles). The auditory tube consists of a bony part and a cartilaginous part (elastic cartilage). The lumen of the tube at the point of their connection - the isthmus of the auditory tube narrows to 1 mm. The upper bony part of the tube is located in the hemicanal of the same name of the muscular-tubal canal of the temporal bone and opens on the anterior wall of the tympanic cavity tympanic hole auditory tube. The lower cartilaginous part, which accounts for 2/3 of the length of the tube, has the appearance of a groove, open at the bottom, formed by the medial and lateral cartilaginous plates and the membranous plate connecting them. In the place where the auditory tube opens on the side wall of the nasopharynx with the pharyngeal opening of the auditory tube, the medial (posterior) plate of the elastic cartilage of the tube thickens and protrudes into the pharyngeal cavity in the form of a roller. The longitudinal axis of the auditory tube from its pharyngeal opening is directed upward and laterally, forming an angle of 40-45° with the horizontal and sagittal planes.
The tensor muscle and the levator palatine muscle originate from the cartilaginous part of the auditory tube. When they contract, the cartilage of the tube and its membranous plate are pulled back, the tube channel expands and air from the pharynx enters the tympanic cavity.
The mucous membrane of the tube forms longitudinal folds and is covered with ciliated epithelium, the movements of the cilia are directed towards the pharynx.
In the mucous membrane of the auditory tube there are many mucous glands of lymphoid tissue, which forms a cluster near the tubal ridge and around the pharyngeal opening of the auditory tube - the tubal tonsil.
Source: https://anatomus.ru/chuvstva/sluh-sred-uho.html
The middle ear consists of cavities and canals communicating with each other: the tympanic cavity, the auditory (Eustachian) tube, the passage to the antrum, the antrum and the cells of the mastoid process (Fig.). The boundary between the outer and middle ear is the eardrum (see).
The structure of the hearing organ (incision along the right external auditory canal): 1 - auricle; 2 and 7 - temporal bone; 3 - hammer; 4 - anvil; 5 - stirrup; 6 - semicircular canals;
8 - auditory nerve;
9 - snail; 10 - auditory (Eustachian) tube; 11 - tympanic cavity; 12 - eardrum;
13 - external auditory canal.
Tympanic cavity located in the pyramid of the temporal bone. Its volume is approximately 1 cm3. The outer wall of the tympanic cavity is formed by the eardrum and bone, which is a continuation of the walls of the external auditory canal (see.
Outer ear). The inner (medial) wall is mostly formed by the capsule of the ear labyrinth (see Inner ear).
It has a cape (promontorium), formed by the main curl of the cochlea, and two windows: one of them, oval (window of the vestibule), is closed by the foot plate (base) of the stapes; the other, round (cochlear window), is closed by a secondary tympanic membrane (round window membrane). The posterior wall borders the mastoid process. In its upper section there is a passage into the antrum. The anterior wall in its lower part borders the internal carotid artery. Above this area is the tympanic opening of the auditory (Eustachian) tube. The upper wall borders the middle cranial fossa. The lower wall borders the bulb of the jugular vein. If there is a developmental anomaly, the bulb can protrude into the lumen of the tympanic cavity, which poses a great danger during paracentesis (see) of the tympanic membrane. In the tympanic cavity there are three auditory ossicles - the malleus, the handle of which is connected to the eardrum (see), and the head (by articulation) to the body of the incus; in the anvil, in addition to its body, short and long legs are distinguished; the latter connects to the head of the stapes. In the stirrup, in addition to the head and neck, there are two legs - anterior and posterior, as well as a foot plate (base).
There are three sections in the tympanic cavity: upper (attic, epitympanum, epitympanic space), middle (mesotympanum) and lower (hypotympanum).
There are two muscles in the tympanic cavity - the stapedius and the tensor tympani. These muscles play a large role in accommodating the sound-conducting system and protecting the inner ear from acoustic trauma.
Sound vibrations are transmitted through the external auditory canal to the eardrum and further along the chain of auditory ossicles (hammer, incus and stapes) to the inner ear.
In this case, they are strengthened both due to the difference in the surfaces of the eardrum and the foot plate of the stapes, and as a result of the lever action of the auditory ossicles.
The auditory (Eustachian) tube is a canal about 3.5 cm long, connecting the tympanic cavity with the nasopharynx. It consists of two parts - bone (tympanic) and membranous-cartilaginous (nasopharyngeal).
The tube is lined with multirow ciliated epithelium. The tube opens mainly during swallowing movements.
This is necessary to ventilate the middle ear and equalize the pressure in it relative to the surrounding environment.
In the mastoid process there is an antrum (cave) - the largest, permanent cell that communicates with the tympanic cavity through a passage into the antrum (aditus ad antrum), as well as with other cells of the process (if they are developed).
The upper wall of the antrum borders on the middle cranial fossa, the medial wall borders on the posterior (sigmoid sinus).
It has great importance in the spread of infection from the middle ear to the cranial cavity (otogenic purulent meningitis, arachnoiditis, brain or cerebellar abscess, sigmoid sinus thrombosis, sepsis).
Rice. 1. Lateral wall of the tympanic cavity. Rice. 2. Medial wall of the tympanic cavity. Rice. 3. Section of the head, carried out along the axis of the auditory tube (lower part of the cut): 1 - ostium tympanicum tubae audltivae; 2 - tegmen tympani; 3 - membrane tympani; 4 - manubrium mallei; 5 - recessus epitympanicus; 6 -caput mallei; 7 -incus; 8 - cellulae mastoldeae; 9 - chorda tympani; 10 - n. facialis; 11 - a. carotis int.; 12 - canalis caroticus; 13 - tuba auditiva (pars ossea); 14 - prominentia canalis semicircularis lat.; 15 - prominentia canalis facialis; 16 - a. petrosus major; 17 - m. tensor tympani; 18 - promontorium; 19 - plexus tympanicus; 20 - steps; 21- fossula fenestrae cochleae; 22 - eminentia pyramidalis; 23 - sinus sigmoides; 24 - cavum tympani; 25 - entrance to meatus acustlcus ext.; 26 - auricula; 27 - meatus acustlcus ext.; 28 - a. et v. temporales superficiales; 29 - glandula parotis; 30 - articulatio temporomandibularis; 31 - ostium pharyngeum tubae auditivae; 32 - pharynx; 33 - cartilago tubae auditivae; 34 - pars cartilaginea tubae auditivae; 35 - n. mandibularis; 36 - a. meningea media; 37 - m. pterygoideus lat.; 38 - in. temporalis.
The middle ear consists of the tympanic cavity, the eustachian tube and the mastoid air cells.
Between the outer and inner ear is the tympanic cavity. Its volume is about 2 cm3. It is lined with mucous membrane, filled with air and contains a number of important elements.
Inside the tympanic cavity there are three auditory ossicles: the malleus, the incus and the stirrup, so named for their resemblance to the indicated objects (Fig. 3). The auditory ossicles are connected to each other by movable joints.
The hammer is the beginning of this chain; it is woven into the eardrum. The anvil occupies a middle position and is located between the malleus and stapes. The stapes is the final link in the chain of auditory ossicles.
On inside The tympanic cavity has two windows: one is round, leading into the cochlea, covered by a secondary membrane (unlike the already described tympanic membrane), the other is oval, into which a stapes is inserted, as if in a frame.
The average weight of the malleus is 30 mg, the incus is 27 mg, and the stapes is 2.5 mg. The malleus has a head, a neck, a short process and a handle. The handle of the hammer is woven into the eardrum. The head of the malleus is connected to the incus joint.
Both of these bones are suspended by ligaments from the walls of the tympanic cavity and can move in response to vibrations of the eardrum. When examining the tympanic membrane, a short process and the handle of the malleus are visible through it.
Rice. 3. Auditory ossicles.
1 - anvil body; 2 - short process of the incus; 3 - long process of the anvil; 4 - rear leg of the stirrup; 5 - foot plate of the stirrup; 6 - hammer handle; 7 - anterior process; 8 - neck of the malleus; 9 - head of the hammer; 10 - malleus-incus joint.
The anvil has a body, short and long processes. With the help of the latter, it is connected to the stirrup. The stirrup has a head, a neck, two legs and a main plate.
The handle of the malleus is woven into the eardrum, and the footplate of the stapes is inserted into the oval window, thereby forming a chain of auditory ossicles.
Sound vibrations travel from the eardrum to the chain of auditory ossicles, which form a lever mechanism.
There are six walls in the tympanic cavity; The outer wall of the tympanic cavity is mainly the eardrum.
But since the tympanic cavity extends upward and downward beyond the tympanic membrane, bone elements, in addition to the tympanic membrane, also participate in the formation of its outer wall.
The upper wall - the roof of the tympanic cavity (tegmen tympani) - separates the middle ear from the cranial cavity (middle cranial fossa) and is a thin bone plate. The inferior wall, or floor of the tympanic cavity, is located slightly below the edge of the eardrum. Below it is the bulb of the jugular vein (bulbus venae jugularis).
The posterior wall borders the pneumatic system of the mastoid process (antrum and cells of the mastoid process). The descending part of the facial nerve passes through the posterior wall of the tympanic cavity, from which the auricular chord (chorda tympani) arises here.
The anterior wall in its upper part is occupied by the mouth of the Eustachian tube, connecting the tympanic cavity with the nasopharynx (see Fig. 1). The lower section of this wall is a thin bone plate that separates the tympanic cavity from the ascending segment of the internal carotid artery.
The inner wall of the tympanic cavity simultaneously forms the outer wall of the inner ear. Between the oval and round windows there is a protrusion on it - a promontory (promontorium), corresponding to the main curl of the cochlea.
On this wall of the tympanic cavity above the oval window there are two elevations: one corresponds to the facial nerve canal passing here directly above the oval window, and the second corresponds to the protrusion of the horizontal semicircular canal, which lies above the facial nerve canal.
There are two muscles in the tympanic cavity: the stapedius muscle and the tensor tympani muscle. The first is attached to the head of the stapes and is innervated facial nerve, the second is attached to the handle of the malleus and is innervated by a branch of the trigeminal nerve.
The Eustachian tube connects the tympanic cavity with the nasopharynx cavity. In the unified International Anatomical Nomenclature, approved in 1960.
on VII International Congress anatomists, the name “Eustachian tube” was replaced by the term “auditory tube” (tuba anditiva). The eustachian tube has bony and cartilaginous parts.
It is covered with a mucous membrane lined with ciliated columnar epithelium. The cilia of the epithelium move towards the nasopharynx. The length of the pipe is about 3.5 cm. In children, the pipe is shorter and wider than in adults.
In a calm state, the tube is closed, since its walls in the narrowest place (at the place where the bone part of the tube transitions into the cartilaginous part) are adjacent to each other. When swallowing movements, the tube opens and air enters the tympanic cavity.
The mastoid process of the temporal bone is located behind the auricle and external auditory canal.
The outer surface of the mastoid process consists of compact bone tissue and ends at the bottom with an apex.
The mastoid process consists of a large number of air (pneumatic) cells separated from each other by bony septa.
Often there are mastoid processes, the so-called diploetic ones, when their basis is spongy bone, and the number of air cells is insignificant.
In some people, especially those suffering from chronic suppurative disease of the middle ear, the mastoid process consists of dense bone and does not contain air cells. These are the so-called sclerotic mastoid processes.
The central part of the mastoid process is a cave - the antrum. It is a large air cell that communicates with the tympanic cavity and with other air cells of the mastoid process.
The upper wall, or roof of the cave, separates it from the middle cranial fossa. In newborns, the mastoid process is absent (not yet developed). It usually develops in the 2nd year of life.
However, the antrum is also present in newborns; it is located above the ear canal, very superficially (at a depth of 2-4 mm) and subsequently moves posteriorly and downward.
The upper border of the mastoid process is the temporal line - a protrusion in the form of a roller, which is like a continuation of the zygomatic process. In most cases, the floor of the middle cranial fossa is located at the level of this line.
On inner surface mastoid process, which faces the posterior cranial fossa, there is a grooved depression in which the sigmoid sinus is located, abducens venous blood from the brain to the bulb of the jugular vein.
The middle ear is supplied with arterial blood mainly from the external and to a lesser extent from the internal carotid arteries. The innervation of the middle ear is carried out by the branches of the glossopharyngeal, facial and sympathetic nerves.
Middle ear pathology- see Aerootitis, Eustachitis, Mastoiditis, Otitis, Otosclerosis.
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