Performs a function that is of great importance for the full functioning of a person. Therefore, it makes sense to study its structure in more detail.
Anatomy of the ears
The anatomical structure of the ears, as well as their component parts, has a significant impact on the quality of hearing. A person’s speech directly depends on the full functioning of this function. Therefore, the healthier the ear, the easier it is for a person to carry out the process of life. It is these features that determine the fact that the correct anatomy of the ear is of great importance.
Initially, it is worth starting to consider the structure of the hearing organ with the auricle, which is the first thing that catches the eye of those who are not experienced in the topic of human anatomy. It is located between the mastoid process on the posterior side and the temporal mandibular joint front. It is thanks to the auricle that a person’s perception of sounds is optimal. In addition, this particular part of the ear is of no small cosmetic importance.
The basis of the auricle can be defined as a plate of cartilage, the thickness of which does not exceed 1 mm. On both sides it is covered with skin and perichondrium. The anatomy of the ear also points to the fact that the only part of the shell that lacks a cartilaginous skeleton is the lobe. It consists of skin-covered fatty tissue. The auricle has a convex inner part and a concave outer part, the skin of which is tightly fused with the perichondrium. Speaking about the inside of the shell, it is worth noting that in this area the connective tissue is much more developed.
It is also worth noting the fact that two-thirds of the length of the external auditory canal is occupied by the membranous-cartilaginous section. As for the bone department, it gets only a third part. The basis of the membranous-cartilaginous section is the continuation of the cartilage of the auricle, which looks like a groove open at the back. Its cartilaginous framework is interrupted by vertically running Santorini fissures. They are covered with fibrous tissue. The boundary of the auditory canal is located exactly in the place where these gaps are located. It is this fact that explains the possibility of developing a disease that appears in the outer ear, in the area of the parotid gland. It is worth understanding that this disease can spread in the reverse order.
Those for whom information on the topic “anatomy of the ears” is relevant should also pay attention to the fact that the membranous cartilaginous section is connected to the bony part of the external auditory canal through fibrous tissue. The narrowest part can be found in the middle of this section. It is called the isthmus.
Within the membranous-cartilaginous section, the skin contains sulfur and sebaceous glands, as well as hair. It is from the secretion of these glands, as well as the scales of the epidermis that have been rejected, that earwax is formed.
Walls of the external auditory canal
The anatomy of the ears includes information about the various walls that are located in the external meatus:
- Upper bone wall. If a fracture occurs in this part of the skull, it may result in liquorrhea and bleeding from the ear canal.
- Front wall. It is located on the border with temporomandibular joint. The movements of the jaw itself are transmitted to the membranous-cartilaginous part of the external passage. Sharp painful sensations can accompany the chewing process if inflammatory processes are present in the area of the anterior wall.
- The anatomy of the human ear concerns the study of the posterior wall of the external auditory canal, which separates the latter from the mastoid cells. At the base of this particular wall there is facial nerve.
- Bottom wall. This part of the external meatus separates it from the salivary parotid gland. Compared to the top one, it is 4-5 mm longer.
Innervation and blood supply to the hearing organs
It is imperative that those who study the structure of the human ear pay attention to these functions. The anatomy of the organ of hearing includes detailed information about its innervation, which is carried out through the trigeminal nerve, the auricular branch of the vagus nerve, and also. Moreover, it is the posterior auricular nerve that supplies the rudimentary muscles of the auricle with nerves, although their functional role can be defined as quite low.
Regarding the topic of blood supply, it is worth noting that the blood supply is provided from the external system carotid artery.
The blood supply directly to the auricle itself is carried out using the superficial temporal and posterior auricular arteries. It is this group of vessels, together with the branches of the maxillary and posterior auricular arteries, that provide blood flow in the deep parts of the ear and the eardrum in particular.
Cartilage receives nutrition from vessels located in the perichondrium.
As part of a topic such as “Anatomy and Physiology of the Ear,” it is worth considering the process of venous outflow in this part of the body and the movement of lymph. Venous blood leaves the ear through the posterior auricular and posterior mandibular veins.
As for lymph, its outflow from the external ear is carried out through nodes that are located in the mastoid process in front of the tragus, as well as under the lower wall of the external auditory canal.
Eardrum
This part of the hearing organ serves as the separation of the outer and middle ear. In essence, we are talking about a translucent fibrous plate that is quite strong and resembles an oval shape.
Without this plate, the ear will not be able to fully function. The anatomy of the structure of the eardrum reveals in sufficient detail: its size is approximately 10 mm, its width is 8-9 mm. An interesting fact is that in children this part of the hearing organ is almost the same as in adults. The only difference comes down to its form - in early age it is round and noticeably thicker. If we take the axis of the external auditory canal as a guide, then in relation to it the eardrum is located obliquely, at an acute angle (approximately 30°).
It is worth noting that this plate is located in the groove of the fibrocartilaginous tympanic ring. Under the influence of sound waves, the eardrum begins to tremble and transmits vibrations to the middle ear.
Tympanic cavity
Clinical anatomy the middle ear includes information about its structure and functions. This part of the hearing organ also includes the auditory tube with a system of air cells. The cavity itself is a slit-like space in which 6 walls can be distinguished.
Moreover, there are three ear bones in the middle ear - the incus, malleus and stirrup. They are connected using small joints. In this case, the hammer is in close proximity to the eardrum. It is he who is responsible for the perception of sound waves transmitted by the membrane, under the influence of which the hammer begins to tremble. Subsequently, the vibration is transmitted to the incus and stapes, and then the inner ear reacts to it. This is the anatomy of the human ears in their middle part.
How does the inner ear work?
This part of the hearing organ is located in the area of the temporal bone and looks like a labyrinth. In this part, the resulting sound vibrations are converted into electrical impulses that are sent to the brain. Only after this process is completely completed is a person able to respond to sound.
It is also important to pay attention to the fact that the human inner ear contains semicircular canals. This is relevant information for those who study the structure of the human ear. The anatomy of this part of the hearing organ looks like three tubes that are bent in the shape of an arc. They are located in three planes. Due to the pathology of this part of the ear, disturbances in the functioning of the vestibular apparatus are possible.
Anatomy of sound production
When sound energy enters the inner ear, it is converted into impulses. Moreover, due to the structure of the ear, the sound wave travels very quickly. The consequence of this process is the appearance of a shear-promoting cover plate. As a result, the stereocilia of hair cells are deformed, which, having entered a state of excitation, transmit information using sensory neurons.
Conclusion
It is easy to see that the structure of the human ear is quite complex. For this reason, it is important to ensure that the hearing organ remains healthy and prevent the development of diseases found in this area. IN otherwise You may encounter a problem such as impaired sound perception. To do this, at the first symptoms, even if they are minor, it is recommended to visit a highly qualified doctor.
The human hearing organ is essential for natural human functioning. The ears are responsible for the receptivity of sound waves, processing into nerve impulses and sending the converted decibels to the brain. In addition, the ear is responsible for performing the balance function.
Despite the external simplicity of the auricle, the design of the hearing organ is considered incredibly complex. This material shows the structure of the human ear.
Ear organ has a paired structure and is located in the temporal part of the cortex of the cerebral hemisphere. The ear organ is characterized by the constant performance of several tasks.
However, among the main functions is considered reception and processing of sounds of different frequencies.
These are then transmitted to the brain and send signals to the body in the form of electrical signals.
The hearing aid perceives both low-frequency sounds and high-frequency sounds up to 2 tens of kHz.
Man receives frequencies above sixteen Hertz. However highest threshold the human ear does not exceed twenty thousand Hertz.
Only the outer area is open to the human eye. In addition, the ear consists from two departments:
- average;
- internal.
Each section of the hearing aid has individual structure and certain functions. The three sections are connected in an elongated auditory tube, which is directed into the brain. For visualization of this picture Look at the cross-sectional photo of the ear.
Composition of the human ear
An exceptional organ in the structure of the body is the organ of hearing. Despite its apparent simplicity, this area has a complex design. The main function of the organ is the distinction of signals, noise, tones and speech, their transformation and increase or decrease.
The following elements are responsible for maintaining all tasks in the ear:
- External part. The structure of this region includes the external concha, which passes into the auditory tube.
- Next is the tympanic region, which separates the outer ear from the middle region.
- The cavity located behind the tympanic region is called the middle ear, which contains the auditory bones and the Eustachian tube.
- Next is the inner region of the ear, which is considered one of the most intricate and intricate in the structure of the described organ. The main task of this cavity is to maintain balance.
- curl;
- – this is a bulge on the outer part of the ear, located on the outer part;
- the paired organ of the tragus is the antihelix. It is located on the top of the lobe;
- earlobe.
Outdoor area
Outer part of the ear that a person sees is called the outer region. It consists of soft tissue and a cartilaginous shell.
Unfortunately, due to soft structure this area,
This leads to severe pain and prolonged treatment.
Young children and people professionally involved in boxing or oriental martial arts suffer most from broken cartilage and bones of the ear.
In addition, the auricle is susceptible to numerous viral and. This most often occurs during the cold season and with frequent touching. with dirty hands to the organ of hearing.
Thanks to the external area, a person has ability to hear sounds. It is through the outer part of the auditory organ that sound frequencies pass into the brain.
It is interesting that, unlike animals, the human hearing organ is immobile and, in addition to the described functions, does not have additional capabilities.
When sound frequencies enter the outer ear, decibels travel through the ear canal to the middle part. To protect and maintain the functioning of the middle area of the ear, it is covered with skin folds. This allows you to further protect your ears and handle any sound frequencies.
The human ear can detect sounds at various distances: from one centimeter to twenty or thirty meters, depending on age.
Sulfur plug.
Helps the outer ear to hear the described sound vibrations auditory tube, which at the end of the passage is transformed into bone tissue. In addition, the auditory tube is responsible for the functioning of the sulfur glands.
Sulfur is a yellow mucous substance necessary to protect the hearing organ from infections, bacteria, dust, foreign objects and small insects.
Usually sulfur is excreted from the body on one's own. However, with improper cleaning or lack of hygiene, sulfur plug. Removing the plug yourself is prohibited, as you may push it further down the ear canal.
To eliminate such an unpleasant problem, contact a specialist. He will rinse the ear with specialized tinctures. In the situation where going to a qualified doctor is impossible, purchase “” or “”. These products will gently remove wax and clean the ear. However, the use of the drugs is allowed when there is a small accumulation of sulfur.
The outer ear passes into middle area . They are separated by the eardrum. After processing sounds in this area, the sound moves to the middle part. For visualization, see the photo of the external sink below.
Structure of the outer area
You can clearly see the structure of the human outer ear with a description in the diagram below. 
The auricle consists of twelve elements of varying structural complexity:
- curl;
- rook;
- Darwin's tubercle;
- ear cavity;
- antitragus;
- lobe;
- helix leg;
- tragus;
- sink bowl;
- lower leg of the antihelix;
- triangular fossa;
- upper leg of the antihelix.
The outer ear is made up of elastic cartilage. The upper and outer edge of the ear is transformed into a curl. The paired organ of the helix is located closer to the passage. It goes around the outer hole and forms two protrusions:
- Antitragus located posteriorly.
- Tragus located in front.
Earlobe represents soft cloth, in which there are no bones and cartilage.
Darwin's tubercle has a pathological structure and is considered an anomaly of the body.
Structure of the human middle ear
Middle ear The human ear is located behind the tympanic region and is considered the main structure of the hearing organ. The volume of the middle part is about one cubic centimeter.
The middle area falls on temporal part heads in which they are located the following elements:
- Drum area.
- The auditory tube unites the nasopharynx and the tympanic part.
- Next is a part of the temporal bone called the mastoid process. It is located behind the outer part of the auditory tube.
Of the presented elements, it is necessary to analyze in more detail the structure of the drum part, since the main functions of processing sound frequencies take place in this area. So the tympanic region is divided into three parts:
- Adjacent to the eardrum first part - hammer. Its function is to receive sound waves and transmit them to the next area.
- After the hammer is the anvil. The main function of this area is the initial processing of sounds and direction to the stapes.
- Directly in front of the inner region of the hearing organ and after the malleus there is a stapes. It processes the received sound and transfers the cleaned signals further.
Main function of the auditory ossicles- This is the conversion of signals, noise, low or high frequencies and transmission from the outer part to the inner ear. In addition, the malleus, incus and stapes are responsible for the following tasks:
- maintaining the tone of the tympanic region and supporting its functioning;
- softening too high sounds;
- increase in low sound waves.
Any trauma or complications afterwards lead to dysfunction stirrups, anvils and hammers. This can cause not only hearing loss, but also loss of sound acuity forever.
It is important to understand that sharp sounds, such as explosions, can cause a reflex contraction and thereby damage the structure of the hearing organ. This will lead to partial or complete hearing loss.
Inner ear
The inner ear is considered one of the most complex components of the described organ. Because of complex design, this area is often called membranous labyrinth.
The inner part is located in the stony region of the temporal bone and is connected to the middle ear by windows of different shapes.
The structure of the human inner ear includes the following elements:
- vestibule of the labyrinth;
- snail;
- semicircular canals.
The last element contains liquids of the form two types:
- Endolymph.
- Perilymph.
In addition, in the inner ear there is vestibular system. It is responsible for the function of balance in space.
As mentioned above, the labyrinth is located inside the bony skull.
The inner ear is separated from the brain by a space filled with viscous fluid. She is responsible for conducting sounds.
A snail is located in the same area.
Snail looks like a spiral channel, which is divided into two parts. This spiral-shaped channel is responsible for the transformation sound vibrations.
Conclusion
Having become familiar with what the ear is made of and its structure, it is important to monitor the health of your ears daily. It's important to support immune system and at the slightest sign of illness, consult a specialist.
Otherwise, main function the organ of hearing can be impaired and lead to serious complications in the form of permanent loss of sensitivity to sounds and noises.
Remember that the hearing organ must perform its functions smoothly. Inflammation of the ears has serious consequences, and any disorder seriously affects a person’s life.
Behind and above the cape is vestibule window niche (fenestra vestibuli), shaped like an oval, elongated in the anteroposterior direction, measuring 3 by 1.5 mm. The vestibule window is closed base of the stirrup (basis stapedis), attached to the edges of the window
Rice. 5.7. Medial wall tympanic cavity and auditory tube: 1 - promontory; 2 - stirrup in the niche of the window of the vestibule; 3 - cochlear window; 4 - first knee of the facial nerve; 5 - ampulla of the lateral (horizontal) semicircular canal; 6 - drum string; 7 - stapedius nerve; 8 - jugular vein; 9 - internal carotid artery; 10 - auditory tube
by using annular ligament (lig. annulare stapedis). In the area of the posterior-inferior edge of the promontory there is snail window niche (fenestra Cochleae), protracted secondary eardrum (membrana tympani secundaria). The window niche of the cochlea faces the posterior wall of the tympanic cavity and is partially covered by the projection of the posteroinferior slope of the promontorium.
Directly above the window of the vestibule in the bony fallopian canal there passes the horizontal knee of the facial nerve, and above and posteriorly there is a protrusion of the ampulla of the horizontal semicircular canal.
Topography facial nerve (n. facialis, VII cranial nerve) has important practical significance. Joining with n. statoacousticus And n. intermedius into the internal auditory canal, the facial nerve passes along its bottom, in the labyrinth it is located between the vestibule and the cochlea. In the labyrinthine section, it departs from the secretory portion of the facial nerve greater stony nerve (n. petrosus major), innervating the lacrimal gland, as well as the mucous glands of the nasal cavity. Before exiting into 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 of the labyrinthine section to the tympanic section is designated as first genus 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 stylomastoid canal and through the foramen of the same name (for. stylomastoideum) extends to the base of the skull. In the immediate vicinity of the pyramidal eminence, the facial nerve gives off a branch to stapedius muscle (m. stapedius), here it departs from the trunk of the facial nerve 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 2/3 of the tongue on its side, secretory fibers to the salivary gland and fibers to the choroid plexuses. The wall of the facial nerve canal in the tympanic cavity is very thin and often has dehiscence, which determines the possibility of inflammation spreading from the middle ear to the nerve and the development of paresis or even paralysis of the facial nerve. Various locations of the facial nerve in the tympanic and mastoid
The ear performs two main functions: the organ of hearing and the organ of balance. The organ of hearing is the main information system that takes part in the development of speech function, and therefore, human mental activity. There are external, middle, and inner ears.
External ear - auricle, external auditory canal
Middle ear – tympanic cavity, auditory tube, mastoid process
Inner ear (labyrinth) - cochlea, vestibule and semicircular canals.
The outer and middle ears provide sound conduction, and the inner ear contains receptors for both the auditory and vestibular analyzers.
Outer ear. The auricle is a curved plate of elastic cartilage, covered on both sides by perichondrium and skin. The auricle is a funnel that provides optimal perception of sounds in a certain direction of sound signals. It also has significant cosmetic value. Such anomalies of the auricle are known as macro- and microotia, aplasia, protrusion, etc. Disfigurement of the auricle is possible with perichondritis (trauma, frostbite, etc.). Its lower part - the lobe - is devoid of cartilage and contains fatty tissue. In the auricle there are distinguished helix (helix), antihelix (anthelix), tragus (tragus), antitragus (antitragus). The helix is part of the external auditory canal. The external auditory canal in an adult consists of two sections: the external - membranous-cartilaginous, equipped with hairs, sebaceous glands and their modifications - earwax glands (1/3); internal – bone, not containing hair and glands (2/3).
The topographic-anatomical relationships of the parts of the auditory canal are of clinical importance. Front wall – borders on the articular capsule of the lower jaw (important for external otitis and injuries). From below – The parotid gland is adjacent to the cartilaginous part. The anterior and lower walls are pierced by vertical slits (Santorini slits) in an amount from 2 to 4, through which suppuration can pass from the parotid gland to the auditory canal, as well as in the opposite direction. Rear – borders the mastoid process. The descending part of the facial nerve passes deep into this wall (radical surgery). Upper – borders on the middle cranial fossa. Superior posterior – is the anterior wall of the antrum. Its omission indicates purulent inflammation cells of the mastoid process.
The external ear is supplied with blood from the external carotid artery system through the superficial temporal (a. temporalis superficialis), occipital (a. occipitalis), posterior auricular and deep auricular arteries (a. auricularis posterior et profunda). Venous outflow is carried out into the superficial temporal (v. temporalis superficialis), external jugular (v. jugularis ext.) and jaw (v. maxillaris) veins. Lymph is drained to the lymph nodes located on the mastoid process and anterior to the auricle. Innervation is carried out by branches of the trigeminal and vagus nerves, as well as from the auricular nerve from the upper cervical plexus. Due to the vagal reflex, with sulfur plugs and foreign bodies, cardialgic phenomena and cough are possible.
The boundary between the outer and middle ear is the eardrum. The diameter of the eardrum (Fig. 1) is approximately 9 mm, thickness 0.1 mm. The eardrum serves as one of the walls of the middle ear, tilted forward and downward. In an adult it is oval in shape. B/p consists of three layers:
external - epidermal, is a continuation of the skin of the external auditory canal,
internal - mucous membrane lining the tympanic cavity,
the fibrous layer itself, located between the mucous membrane and the epidermis and consisting of two layers of fibrous fibers - radial and circular.
The fibrous layer is poor in elastic fibers, so the eardrum is low-elastic and can rupture under sudden pressure fluctuations or very strong sounds. Usually, after such injuries, a scar subsequently forms due to the regeneration of the skin and mucous membrane; the fibrous layer does not regenerate.
In the b/p there are two parts: tense (pars tensa) and loose (pars flaccida). The tense part is inserted into the bone tympanic ring and has a middle fibrous layer. Loose or relaxed, it is attached to a small notch of the lower edge of the squama of the temporal bone; this part does not have a fibrous layer.
On otoscopic examination, the color of the b/p is pearlescent or pearl-gray with a slight sheen. For the convenience of clinical otoscopy, the b/p is mentally divided into four segments (anterosuperior, anterioinferior, posterosuperior, posteroinferior) by two lines: one is a continuation of the handle of the hammer to the lower edge of the b/p, and the second runs perpendicular to the first through the navel of the b/p.
Middle ear. The tympanic cavity is a prismatic space in the thickness of the base of the pyramid of the temporal bone with a volume of 1-2 cm³. It is lined with a mucous membrane that covers all six walls and from behind passes into the mucous membrane of the mastoid cells, and in front into the mucous membrane of the auditory tube. It is represented by single-layer squamous epithelium, with the exception of the mouth of the auditory tube and the bottom of the tympanic cavity, where it is covered with ciliated columnar epithelium, the movement of the cilia is directed towards the nasopharynx.
External (membranous) The wall of the tympanic cavity over a larger extent is formed by the inner surface of the ear canal, and above it - by the upper wall of the bony part of the auditory canal.
Internal (labyrinth) the wall is also the outer wall of the inner ear. In its upper section there is a window of the vestibule, closed by the base of the stapes. Above the window of the vestibule there is a protrusion of the facial canal, below the window of the vestibule there is a round-shaped elevation called the promontory (promontorium), corresponding to the protrusion of the first curl of the cochlea. Below and posterior to the promontory there is a fenestra cochlea, closed by a secondary b/p.
Upper (tire) the wall is a rather thin bone plate. This wall separates the middle cranial fossa from the tympanic cavity. Dehiscences are often found in this wall.
Lower (jugular) wall - formed by the petrous part of the temporal bone and is located 2–4.5 mm below the b/p. It borders on the bulb of the jugular vein. Often in the jugular wall there are numerous small cells that separate the bulb of the jugular vein from the tympanic cavity; sometimes dehiscence is observed in this wall, which facilitates the penetration of infection.
Anterior (sleepy) the wall in the upper half is occupied by the tympanic orifice of the auditory tube. Its lower part borders the canal of the internal carotid artery. Above the auditory tube is the hemicanal of the tensor muscle eardrum(m. tensoris tympani). The bone plate separating the internal carotid artery from the mucous membrane of the tympanic cavity is penetrated by thin tubules and often has dehiscence.
Posterior (mastoid) the wall borders the mastoid process. In the upper section of its back wall there is an entrance to the cave. The canal of the facial nerve passes deep into the posterior wall; the stapedius muscle begins from this wall.
Clinically, the tympanic cavity is conventionally divided into three sections: lower (hypotympanum), middle (mesotympanum), upper or attic (epitympanum).
The auditory ossicles, which are involved in sound conduction, are located in the tympanic cavity. The auditory ossicles - malleus, incus, stapes - are a closely connected chain located between the tympanic membrane and the window of the vestibule. And through the window of the vestibule, the auditory ossicles transmit sound waves to the fluid of the inner ear.
Hammer – it distinguishes between a head, a neck, a short process and a handle. The handle of the malleus is fused with the anvil, a short process protrudes outward from the upper portion of the anvil, and the head articulates with the body of the incus.
Anvil – it has a body and two legs: short and long. A short leg is placed at the entrance to the cave. The long leg connects to the stirrup.
Stirrup – it distinguishes head, front and rear legs, connected to each other by a plate (base). The base covers the window of the vestibule and is strengthened with the window using an annular ligament, due to which the stapes is movable. And this ensures the constant transmission of sound waves into the fluid of the inner ear.
Middle ear muscles. Tensor tympani muscle (m. tensor tympani), innervated trigeminal nerve. The stapes muscle (m. stapedius) is innervated by a branch of the facial nerve (n. stapedius). The muscles of the middle ear are completely hidden in the bone canals; only their tendons pass into the tympanic cavity. They are antagonists and contract reflexively, protecting the inner ear from excessive amplitude of sound vibrations. Sensitive innervation of the tympanic cavity is provided by the tympanic plexus.
The auditory or pharyngotympanic tube connects the tympanic cavity with the nasopharynx. The auditory tube consists of bone and membranous-cartilaginous sections, opening into the tympanic cavity and nasopharynx, respectively. The tympanic opening of the auditory tube opens in the upper part of the anterior wall of the tympanic cavity. The pharyngeal opening is located on the lateral wall of the nasopharynx at the level of the posterior end of the inferior turbinate, 1 cm posterior to it. The hole lies in a fossa bounded above and behind by a protrusion of the tubal cartilage, behind which there is a depression - the Rosenmüllerian fossa. The mucous membrane of the tube is covered with multinucleated ciliated epithelium (the movement of the cilia is directed from the tympanic cavity to the nasopharynx).
Mastoid process – bone formation, according to the type of structure they distinguish: pneumatic, diploetic (consists of spongy tissue and small cells), sclerotic. The mastoid process communicates with the cave through the entrance to the cave (aditus ad antrum). top part tympanic cavity - epitympanum (attic). In the pneumatic type of structure, the following groups of cells are distinguished: threshold, perianthral, angular, zygomatic, perisinous, perifacial, apical, perilabyrinthine, retrolabyrinthine. At the border of the posterior cranial fossa and mastoid cells there is an S-shaped depression to accommodate the sigmoid sinus, which drains venous blood from the brain to the jugular vein bulb. Sometimes the sigmoid sinus is located close to the ear canal or superficially, in this case they speak of sinus previa. This must be kept in mind when performing surgery on the mastoid process.
The blood supply to the middle ear is carried out by branches of the external and internal carotid arteries. Venous blood flows into the pharyngeal plexus, the bulb of the jugular vein and the middle cerebral vein. Lymphatic vessels carry lymph to the retropharyngeal lymph nodes and deep nodes. The innervation of the middle ear comes from the glossopharyngeal, facial and trigeminal nerves.
Due to topographic-anatomical proximity facial nerve Let us trace its course to the formations of the temporal bone. The trunk of the facial nerve is formed in the region of the cerebellopontine triangle and is directed together with the VIII cranial nerve into the internal auditory canal. In the thickness of the petrous part of the temporal bone, near the labyrinth, its petrous ganglion is located. In this area, the greater petrosal nerve branches off from the trunk of the facial nerve, containing parasympathetic fibers for the lacrimal gland. Next, the main trunk of the facial nerve passes through the thickness of the bone and reaches the medial wall of the tympanic cavity, where it turns posteriorly at a right angle (the first genu). The bony (fallopian) canal of the nerve (canalis facialis) is located above the window of the vestibule, where the trunk of the nerve can be damaged during surgical interventions. At the level of the entrance to the cave, the nerve in its bone canal is directed steeply downward (the second genu) and exits the temporal bone through the stylomastoid foramen (foramen stylomastoideum), breaking up in a fan shape into separate branches, the so-called crow's foot (pes anserinus), which innervate the facial muscles. At the level of the second genu, the stapedius departs from the facial nerve, and more caudally, almost at the exit of the main trunk from the stylomastoid foramen, the chorda tympani. The latter passes in a separate tubule, penetrates the tympanic cavity, moving anteriorly between the long leg of the incus and the handle of the malleus, and leaves the tympanic cavity through the petrotympanic (Glaserian) fissure (fissura petrotympanical).
Inner ear lies in the thickness of the pyramid of the temporal bone, two parts are distinguished in it: the bony and membranous labyrinth. The bony labyrinth includes the vestibule, cochlea, and three bony semicircular canals. The bony labyrinth is filled with fluid - perilymph. The membranous labyrinth contains endolymph.
The vestibule is located between the tympanic cavity and the internal auditory canal and is represented by an oval-shaped cavity. The outer wall of the vestibule is the inner wall of the tympanic cavity. The inner wall of the vestibule forms the floor of the internal auditory canal. There are two depressions on it - spherical and elliptical, separated from each other by a vertically running ridge of the vestibule (crista vestibule).
The bony semicircular canals are located in the posteroinferior part of the bone labyrinth in three mutually perpendicular planes. There are lateral, anterior and posterior semicircular canals. These are arched curved tubes in each of which there are two ends or bone legs: expanded or ampullary and unexpanded or simple. The simple bony pedicles of the anterior and posterior semicircular canals join to form a common bony pedicle. The canals are also filled with perilymph.
The bony cochlea begins in the anterioinferior section of the vestibule with a canal that bends spirally and forms 2.5 turns, as a result of which it is called the spiral canal of the cochlea. There is a base and apex of the cochlea. The spiral channel winds around a cone-shaped bone shaft and ends blindly at the apex of the pyramid. The bone plate does not reach the opposite outer wall of the bony cochlea. The continuation of the spiral bone plate is the tympanic plate of the cochlear duct (main membrane), which reaches the opposite wall of the bone canal. The width of the spiral bone plate gradually narrows towards the apex, and the width of the tympanic wall of the cochlear duct increases accordingly. Thus, the shortest fibers of the tympanic wall of the cochlear duct are located at the base of the cochlea, and the longest at the apex.
The spiral bone plate and its continuation, the tympanic wall of the cochlear duct, divide the cochlear canal into two floors: the upper one, the scala vestibule, and the lower one, the scala tympani. Both scalae contain perilymph and communicate with each other through an opening at the apex of the cochlea (helicotrema). The scala vestibule borders the fenestra vestibule, closed by the base of the stapes; the scala tympani borders the fenestra cochlea, closed by the secondary tympanic membrane. The perilymph of the inner ear communicates with the subarachnoid space through the perilymphatic duct (cochlear aqueduct). In this regard, suppuration of the labyrinth can cause inflammation of the soft meninges.
The membranous labyrinth is suspended in the perilymph, filling the bony labyrinth. In the membranous labyrinth, two apparatuses are distinguished: vestibular and auditory.
The hearing aid is located in the membranous cochlea. The membranous labyrinth contains endolymph and is a closed system.
The membranous cochlea is a spirally wrapped canal - the cochlear duct, which, like the cochlea, makes 2½ turns. In cross section, the membranous cochlea has a triangular shape. It is located in the upper floor of the bony cochlea. The wall of the membranous cochlea, bordering the scala tympani, is a continuation of the spiral bone plate - the tympanic wall of the cochlear duct. The wall of the cochlear duct, bordering the scala vestibule - the vestibular plate of the cochlear duct, also extends from the free edge of the bony plate at an angle of 45º. The outer wall of the cochlear duct is part of the outer bony wall of the cochlear canal. On the spiral ligament adjacent to this wall there is a vascular strip. The tympanic wall of the cochlear duct consists of radial fibers arranged in the form of strings. Their number reaches 15,000 - 25,000, their length at the base of the cochlea is 80 microns, at the apex - 500 microns.
The spiral organ (Corti) is located on the tympanic wall of the cochlear duct and consists of highly differentiated hair cells, supporting columnar cells and supporting Deiters cells.
The upper ends of the inner and outer rows of columnar cells are inclined towards each other, forming a tunnel. The outer hair cell is equipped with 100 - 120 hairs - stereocilia, which have a thin fibrillar structure. The plexuses of nerve fibers around the hair cells are directed through tunnels to the spiral ganglion at the base of the spiral bone plate. There are up to 30,000 ganglion cells in total. The axons of these ganglion cells connect in the internal auditory canal to form the cochlear nerve. Above the spiral organ is a covering membrane, which begins near the origin of the vestibular wall of the cochlear duct and covers the entire spiral organ in the form of a canopy. Stereocilia of hair cells penetrate the integumentary membrane, which plays a special role in the process of sound reception.
The internal auditory canal begins with the internal auditory opening, located on the posterior edge of the pyramid, and ends with the bottom of the internal auditory canal. It contains the periocochlear nerve (VIII), consisting of the superior vestibular root and the inferior cochlear root. Above it is the facial nerve and next to it is the intermediate nerve.
And morphologists call this structure organelukha and balance (organum vestibulo-cochleare). It has three sections:
- external ear (external auditory canal, auricle with muscles and ligaments);
- middle ear (tympanic cavity, mastoid appendages, auditory tube)
- (membranous labyrinth located in the bony labyrinth inside the bone pyramid).
1. The outer ear concentrates sound vibrations and directs them to the external auditory opening.
2. The auditory canal conducts sound vibrations to the eardrum
3. The eardrum is a membrane that vibrates under the influence of sound.
4. The malleus with its handle is attached to the center of the eardrum with the help of ligaments, and its head is connected to the incus (5), which, in turn, is attached to the stapes (6).
Tiny muscles help transmit sound by regulating the movement of these ossicles.
7. The Eustachian (or auditory) tube connects the middle ear to the nasopharynx. When the ambient air pressure changes, the pressure on both sides of the eardrum is equalized through auditory tube.
The organ of Corti consists of a number of sensory, hair-bearing cells (12) that cover the basilar membrane (13). Sound waves are picked up by hair cells and converted into electrical impulses. These electrical impulses are then transmitted along the auditory nerve (11) to the brain. Auditory nerve consists of thousands of tiny nerve fibers. Each fiber starts from a specific part of the cochlea and transmits a specific sound frequency. Low-frequency sounds are transmitted through fibers emanating from the apex of the cochlea (14), and high-frequency sounds are transmitted through fibers connected to its base. Thus, the function of the inner ear is to convert mechanical vibrations into electrical ones, since the brain can only perceive electrical signals.
Outer ear is a sound-collecting device. The external auditory canal conducts sound vibrations to the eardrum. The eardrum, which separates the outer ear from the tympanic cavity, or middle ear, is a thin (0.1 mm) partition shaped like an inward funnel. The membrane vibrates under the action of sound vibrations coming to it through the external auditory canal.
Sound vibrations are picked up by the ears (in animals they can turn towards the sound source) and transmitted through the external auditory canal to the eardrum, which separates the outer ear from the middle ear. Catching sound and the entire process of listening with two ears - so-called binaural hearing - is important for determining the direction of sound. Sound vibrations coming from the side reach the nearest ear a few ten-thousandths of a second (0.0006 s) earlier than the other. This insignificant difference in the time of arrival of sound to both ears is enough to determine its direction.
Middle ear is a sound-conducting device. It is an air cavity that connects to the nasopharynx cavity through the auditory (Eustachian) tube. Vibrations from the eardrum through the middle ear are transmitted by 3 auditory ossicles connected to each other - the hammer, incus and stapes, and the latter, through the membrane of the oval window, transmits these vibrations to the fluid located in the inner ear - perilymph.
Due to the peculiarities of the geometry of the auditory ossicles, vibrations of the eardrum of reduced amplitude but increased strength are transmitted to the stapes. In addition, the surface of the stapes is 22 times smaller than the eardrum, which increases its pressure on the oval window membrane by the same amount. As a result of this, even weak sound waves acting on the eardrum can overcome the resistance of the membrane of the oval window of the vestibule and lead to vibrations of the fluid in the cochlea.
With strong sounds, special muscles reduce the mobility of the eardrum and auditory ossicles, adapting hearing aid to such changes in the stimulus and protecting the inner ear from destruction.
Thanks to the connection of the air cavity of the middle ear with the cavity of the nasopharynx through the auditory tube, it becomes possible to equalize the pressure on both sides of the eardrum, which prevents its rupture during significant changes in pressure in the external environment - when diving under water, climbing to a height, shooting, etc. This is the barofunction of the ear .
There are two muscles in the middle ear: the tensor tympani and the stapedius. The first of them, contracting, increases the tension of the eardrum and thereby limits the amplitude of its vibrations during strong sounds, and the second fixes the stapes and thereby limits its movements. The reflex contraction of these muscles occurs 10 ms after the onset of a strong sound and depends on its amplitude. This automatically protects the inner ear from overload. In case of instantaneous strong irritations (impacts, explosions, etc.), this protective mechanism does not have time to work, which can lead to hearing impairment (for example, among bombers and artillerymen).
Inner ear is a sound-perceiving apparatus. It is located in the pyramid of the temporal bone and contains the cochlea, which in humans forms 2.5 spiral turns. The cochlear canal is divided by two partitions, the main membrane and the vestibular membrane into 3 narrow passages: upper (scala vestibular), middle (membranous canal) and lower (scala tympani). At the top of the cochlea there is an opening that connects the upper and lower canals into a single one, going from the oval window to the top of the cochlea and then to the round window. Its cavity is filled with fluid - peri-lymph, and the cavity of the middle membranous canal is filled with a fluid of a different composition - endolymph. In the middle channel there is a sound-perceiving apparatus - the organ of Corti, in which there are mechanoreceptors of sound vibrations - hair cells.
The main route of delivery of sounds to the ear is airborne. The approaching sound vibrates the eardrum, and then through the chain of auditory ossicles the vibrations are transmitted to the oval window. At the same time, vibrations of the air in the tympanic cavity also occur, which are transmitted to the membrane of the round window.
Another way of delivering sounds to the cochlea is tissue or bone conduction . In this case, the sound directly acts on the surface of the skull, causing it to vibrate. Bone pathway for sound transmission becomes of great importance if a vibrating object (for example, the stem of a tuning fork) comes into contact with the skull, as well as in diseases of the middle ear system, when the transmission of sounds through the chain of auditory ossicles is disrupted. In addition to the air path for conducting sound waves, there is a tissue, or bone, path.
Under the influence of airborne sound vibrations, as well as when vibrators (for example, a bone telephone or a bone tuning fork) come into contact with the integument of the head, the bones of the skull begin to vibrate (the bone labyrinth also begins to vibrate). Based on the latest data (Bekesy and others), it can be assumed that sounds propagating along the bones of the skull only excite the organ of Corti if, similar to air waves, they cause arching of a certain section of the main membrane.
The ability of the skull bones to conduct sound explains why to the person himself his voice, recorded on tape, seems foreign when the recording is played back, while others easily recognize it. The fact is that the tape recording does not reproduce your entire voice. Usually, when talking, you hear not only those sounds that your interlocutors also hear (that is, those sounds that are perceived due to air-liquid conduction), but also those low-frequency sounds, the conductor of which is the bones of your skull. However, when listening to a tape recording of your own voice, you hear only what could be recorded - sounds whose conductor is air.
Binaural hearing . Humans and animals have spatial hearing, that is, the ability to determine the position of a sound source in space. This property is based on the presence of binaural hearing, or listening with two ears. It is also important for him to have two symmetrical halves at all levels. The acuity of binaural hearing in humans is very high: the position of the sound source is determined with an accuracy of 1 angular degree. The basis for this is the ability of neurons in the auditory system to evaluate interaural (inter-ear) differences in the time of arrival of sound to the right and left ear and the intensity of sound in each ear. If the sound source is located away from the midline of the head, the sound wave arrives at one ear slightly earlier and has great strength than on the other ear. Assessing the distance of a sound source from the body is associated with a weakening of the sound and a change in its timbre.
When the right and left ears are stimulated separately via headphones, a delay between sounds of as little as 11 μs or a 1 dB difference in the intensity of the two sounds results in an apparent shift in the localization of the sound source from the midline towards an earlier or stronger sound. The auditory centers are acutely attuned to a certain range of interaural differences in time and intensity. Cells have also been found that respond only to a certain direction of movement of a sound source in space.