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The auditory ossicles transmit vibrations to which window. Middle ear

Everyone knows that the human ear has a complex structure: outer, middle and inner ear. The middle ear plays an important role in the entire auditory process, as it performs a sound-conducting function. Diseases occurring in the middle ear pose a direct threat to human life. Therefore, studying the structure, functions and methods of protecting the middle ear from infections is a very urgent task.

Organ structure

The middle ear is located deep in the temporal bone and is represented by the following organs:

  • tympanic cavity;

The middle ear is structured as a collection of air cavities. Its central part is the tympanic cavity - the area between the i. It has a mucous surface and resembles a prism or tambourine. The tympanic cavity is separated from the skull by an upper wall.

The anatomy of the middle ear provides for its separation by a bony wall from the inner ear. There are 2 holes in this wall: round and oval. Each opening, or window, is protected by an elastic membrane.

The middle ear cavity contains and, which transmit sound vibrations. These bones include the malleus, incus and stirrup. The names of the bones arose in connection with the peculiarities of their structure. The mechanism of interaction of the auditory ossicles resembles a system of levers. The malleus, incus and stirrup are connected by joints and ligaments. In the center of the eardrum is the handle of the malleus, its head is connected to the incus, and it is connected by a long process to the head of the stapes. The stapes enters the foramen ovale, behind which is the vestibule - the part of the inner ear filled with fluid. All bones are covered with a mucous membrane.

An important element of the middle ear is the auditory tube. It connects the tympanic cavity with the external environment. The mouth of the tube is located at the level of the hard palate and opens into the nasopharynx. The opening of the auditory tube is closed when there are no sucking or swallowing movements. There is one feature of the structure of the tube in newborns: it is wider and shorter than in an adult. This fact makes it easier for viruses to penetrate.

The mastoid process is a process of the temporal bone that is located behind it. The structure of the appendage is cavitary, since it contains cavities filled with air. The cavities communicate with each other through narrow slits, which allows the middle ear to improve its acoustic properties.

The structure of the middle ear also suggests the presence of muscles. The tensor tympani muscle and the stapedius muscle are the smallest muscles in the entire body. With their help, the auditory ossicles are supported and adjusted. In addition, the muscles of the middle ear provide accommodation of the organ to sounds of varying heights and strengths.

Purpose and functions

The functioning of the hearing organ is impossible without this element. The middle ear contains the most important components, which together perform the function of sound conduction. Without the middle ear, this function could not be realized and the person would not be able to hear.


The auditory ossicles provide bone conduction of sound and mechanical transmission of vibrations to the oval window of the vestibule. 2 small muscles perform a number of important tasks for hearing:

  • maintain the tone of the eardrum and the mechanism of the auditory ossicles;
  • protect the inner ear from strong sound irritations;
  • provide accommodation of the sound-conducting apparatus to sounds of varying strength and height.

Based on the functions performed by the middle ear with all its components, we can conclude that without it, the auditory function would be unfamiliar to a person.

Middle ear diseases

Ear diseases are one of the most unpleasant ailments for humans. They pose a great danger not only to health, but also to human life. The middle ear, as the most important part of the auditory organ, is susceptible to various diseases. Leaving middle ear disease untreated, a person risks becoming hard of hearing and significantly reducing the quality of his life.

It ends with the tympanic membrane, blindly closing the auditory canal, bordering:

  • with the joint of the lower jaw, when chewing, the movement is transmitted to the cartilaginous part of the passage;
  • with cells of the mastoid process, facial nerve;
  • with the salivary gland.

The membrane between the outer ear and the middle ear is an oval translucent fibrous plate, measuring 10 mm in length, 8-9 mm in width, 0.1 mm in thickness. The membrane area is about 60 mm 2.

The plane of the membrane is located obliquely to the axis of the ear canal at an angle, drawn funnel-shaped into the cavity. The maximum tension of the membrane is in the center. Behind the eardrum is the middle ear cavity.

There are:

  • middle ear cavity (tympanum);
  • auditory tube (Eustachian tube);
  • auditory ossicles.

Tympanic cavity

The cavity is located in the temporal bone, its volume is 1 cm 3. It houses the auditory ossicles, articulated with the eardrum.

The mastoid process, consisting of air cells, is located above the cavity. It houses a cave - an air cell that serves in the anatomy of the human ear as the most characteristic landmark when performing any operations on the ear.

Eustachian tube


The formation is 3.5 cm long, with a lumen diameter of up to 2 mm. Its upper mouth is located in the tympanic cavity, the lower pharyngeal mouth opens in the nasopharynx at the level of the hard palate.

The auditory tube consists of two sections, separated by its narrowest point - the isthmus. A bony part extends from the tympanic cavity, and below the isthmus there is a membranous-cartilaginous part.

The walls of the tube in the cartilaginous section are normally closed, opening slightly during chewing, swallowing, and yawning. The expansion of the lumen of the tube is provided by two muscles associated with the velum palatine. The mucous membrane is lined with epithelium, the cilia of which move towards the pharyngeal mouth, providing the drainage function of the pipe.


The smallest bones in human anatomy, the auditory ossicles of the ear, are designed to conduct sound vibrations. In the middle ear there is a chain: malleus, stirrup, incus.

The malleus is attached to the tympanic membrane, its head articulates with the incus. The incus process is connected to the stapes, which is attached at its base to the window of the vestibule, located on the labyrinthine wall between the middle and inner ear.

The structure is a labyrinth consisting of a bone capsule and a membranous formation that follows the shape of the capsule.

In the bone labyrinth there are:

  • vestibule;
  • snail;
  • 3 semicircular canals.

Snail

The bone formation is a three-dimensional spiral of 2.5 turns around the bone rod. The width of the base of the cochlear cone is 9 mm, the height is 5 mm, the length of the bone spiral is 32 mm. A spiral plate extends from the bone rod into the labyrinth, which divides the bone labyrinth into two channels.

At the base of the spiral lamina are the auditory neurons of the spiral ganglion. The bony labyrinth contains perilymph and a membranous labyrinth filled with endolymph. The membranous labyrinth is suspended in the bony labyrinth using cords.

Perilymph and endolymph are functionally connected.

  • Perilymph – its ionic composition is close to blood plasma;
  • endolymph - similar to intracellular fluid.


Violation of this balance leads to increased pressure in the labyrinth.

The cochlea is an organ in which physical vibrations of the perilymph fluid are converted into electrical impulses from the nerve endings of the cranial centers, which are transmitted to the auditory nerve and the brain. At the top of the cochlea there is an auditory analyzer - the organ of Corti.

The vestibule

The most ancient anatomically middle part of the inner ear is the cavity bordering the scala cochlea through a spherical sac and semicircular canals. On the wall of the vestibule leading into the tympanic cavity, there are two windows - an oval window, covered by the stapes, and a round window, which represents the secondary eardrum.

Features of the structure of the semicircular canals

All three mutually perpendicular bony semicircular canals have a similar structure: they consist of an expanded and simple pedicle. Inside the bones there are membranous canals that repeat their shape. The semicircular canals and vestibular sacs make up the vestibular apparatus and are responsible for balance, coordination, and determining the position of the body in space.

In a newborn, the organ is not formed and differs from an adult in a number of structural features.

Auricle

  • The shell is soft;
  • the lobe and curl are weakly expressed and are formed by the age of 4 years.

auditory canal

  • The bone part is not developed;
  • the walls of the passage are located almost closely;
  • The drum membrane lies almost horizontally.

  • Almost adult size;
  • In children, the eardrum is thicker than in adults;
  • covered with mucous membrane.

Tympanic cavity


In the upper part of the cavity there is an open gap, through which, in acute otitis media, the infection can penetrate the brain, causing the phenomenon of meningism. In an adult, this gap closes.

The mastoid process in children is not developed; it is a cavity (atrium). The development of the appendage begins at the age of 2 years and ends by 6 years.

Eustachian tube

In children, the auditory tube is wider, shorter than in adults, and located horizontally.

The complex paired organ receives sound vibrations of 16 Hz - 20,000 Hz. Injuries and infectious diseases reduce the sensitivity threshold and lead to gradual hearing loss. Advances in medicine in the treatment of ear diseases and hearing aids make it possible to restore hearing in the most difficult cases of hearing loss.

Video about the structure of the auditory analyzer

The middle ear (auris media) consists of several interconnected air cavities: the tympanic cavity (cavum tympani), the auditory tube (tuba auditiva), the entrance to the cave (aditus ad antrum), the cave (antrum) and the associated air cells of the mastoid process (cellulae mastoidea). Through the auditory tube, the middle ear communicates with the nasopharynx; under normal conditions, this is the only communication between all cavities of the middle ear and the external environment.

1 - horizontal semicircular canal; 2 - canal of the facial nerve; 3 - roof of the tympanic cavity; 4 - window of the vestibule; 5 - muscle semi-channel; 6 - tympanic opening of the auditory tube; 7 - canal of the carotid artery; 8 - promontorium; 9 - tympanic nerve; 10 - jugular fossa; 11 - cochlear window; 12 - drum string; 13 - pyramidal process; 14 - entrance to the cave.

Drum cavity (Fig. 4.4). The tympanic cavity can be compared to an irregularly shaped cube with a volume of up to 1 cm3. It has six walls: upper, lower, anterior, posterior, outer and inner.

The upper wall, or roof, of the tympanic cavity (tegmen tympani) is represented by a bone plate 1-6 mm thick. It separates the tympanic cavity from the middle cranial fossa. There are small holes in the roof through which vessels pass that carry blood from the dura mater to the mucous membrane of the middle ear. Sometimes dehiscences form in the upper wall; in these cases, the mucous membrane of the tympanic cavity is directly adjacent to the dura mater.

In newborns and children of the first years of life, on the border between the pyramid and the scales of the temporal bone there is an open fissure (fissura petrosquamosa), which causes the occurrence of brain symptoms in them during acute inflammation of the middle ear. Subsequently, a suture (sutura petrosquamosa) is formed at this place and the connection with the cranial cavity in this place is eliminated.

The lower (jugular) wall, or the bottom of the tympanic cavity (paries jugularis), borders on the underlying jugular fossa (fossa jugularis), in which the bulb of the jugular vein (bulbus) is located venae jugularis). The more the fossa protrudes into the tympanic cavity, the thinner the bone wall. The lower wall may be very thin or have dehiscences, through which the vein bulb sometimes protrudes into the tympanic cavity. This makes it possible for the jugular vein bulb to be injured, accompanied by severe bleeding, during paracentesis or careless scraping of granulations from the bottom of the tympanic cavity.

The anterior wall, tubular or carotid (paries tubaria, s.caroticus), of the tympanic cavity is formed by a thin bone plate, outside of which the internal carotid artery is located. There are two openings in the anterior wall, the upper of which, narrow, leads into the semicanal for the muscle that stretches the tympanic membrane (semicanalis m.tensoris tympani), and the lower, wide, leads into the tympanic opening of the auditory tube (ostium tympanicum tybae auditivae). In addition, the anterior wall is pierced by thin canaliculi (canaliculi caroticotympanici), through which vessels and nerves pass into the tympanic cavity; in some cases it has dehiscence.

The posterior (mastoid) wall of the tympanic cavity (paries mastoideus) borders the mastoid process. In the upper part of this wall there is a wide passage (aditus adantrum), connecting the supratympanic recess - the attic (attic) with the permanent cell of the mastoid process - the cave (antrum mastoideum). Below this passage there is a bony protrusion - a pyramidal process, from which the stapedius muscle (m.stapedius) begins. On the outer surface of the pyramidal process there is a tympanic foramen (apertura tympanica canaliculi chordae), through which the tympanic chord (chorda tympani), extending from the facial nerve, enters the tympanic cavity. The descending limb of the facial nerve canal passes through the thickness of the lower part of the posterior wall.

The outer (membranous) wall of the tympanic cavity (paries membranaceus) is formed by the tympanic membrane and partially in the attic area by a bone plate that extends from the upper bone walls of the external auditory canal.

Internal (labyrinthine, medial, promotorial ) the wall of the tympanic cavity (paries labyrinthicus) is the outer wall of the labyrinth and separates it from the cavity of the middle ear. In the middle part of this wall there is an oval-shaped elevation - a promontory (promontorium), formed by the protrusion of the main curl of the cochlea.

Posterior and superior to the promontory there is a niche for the window of the vestibule (oval window according to the old nomenclature; fenestra vestibuli), closed by the base of the stapes (basis stapedis). The latter is attached to the edges of the window by means of an annular ligament (lig. annulare). In the direction posterior and downward from the promontory there is another niche, at the bottom of which there is a cochlear window (round window according to the old nomenclature; fenestra cochleae), leading into the cochlea and closed by a secondary tympanic membrane (membrana ympany secundaria), which consists of three layers: outer - mucous, middle - connective tissue and internal - endothelial.

How does sound perception occur?

The sound waves reach the outer concha and are transmitted to the outer ear, where they cause the eardrum to move. These vibrations are amplified by the auditory ossicles and transmitted to the membrane of the middle window. In the inner ear, vibrations provoke the movement of perilymph.

If the vibrations are quite strong, then they reach the endolymph, which, in turn, provokes irritation of the hair cells (receptors) of the organ of Corti. Sounds of different pitches move fluid in different directions, which is detected by nerve cells. They convert mechanical vibrations into a nerve impulse, which reaches the temporal lobe of the cortex through the auditory nerve.



A sound wave entering the ear is converted into a nerve impulse

The physiology of sound perception is difficult to study, since sound causes a slight displacement of the membrane, fluid vibrations are very small, and the anatomical region itself is small and located in the capsule of the labyrinth.

The anatomy of the human ear allows it to detect waves from 16 to 20 thousand vibrations per second. This is not much compared to other animals. For example, a cat perceives ultrasound and is able to detect up to 70 thousand vibrations per second. With age, a person's sound perception deteriorates.

Thus, a thirty-five-year-old person can perceive sound no higher than 14 thousand Hz, and those over 60 years old can only perceive up to 1 thousand vibrations per second.

Ear diseases

The pathological process occurring in the ears can be inflammatory, non-inflammatory, traumatic or fungal. Non-inflammatory diseases include otosclerosis, vestibular neuritis, Meniere's disease.

Otosclerosis develops as a result of pathological tissue proliferation, due to which the auditory ossicles lose mobility and deafness occurs. Most often, the disease begins during puberty and by the age of 30 a person has severe symptoms.

Meniere's disease occurs due to the accumulation of fluid in a person's inner ear. Signs of pathology: nausea, vomiting, tinnitus, dizziness, difficulties with coordination. Vestibular neuritis may develop.

This pathology, if it occurs in isolation, does not cause hearing impairment, however, it can provoke nausea, dizziness, vomiting, tremor, headache, and convulsions. The most common ear diseases are inflammatory in nature.

Depending on the location of the inflammation, there are:

  • otitis externa;
  • otitis media;
  • internal otitis;
  • labyrinthitis.

Occur as a result of the development of infection.



If otitis media is ignored, the auditory nerve is affected, which can lead to irreversible deafness

Hearing decreases as a result of the formation of plugs in the outer ear. Normally, sulfur is excreted on its own, but if its production is increased or its viscosity changes, it can accumulate and block the movement of the eardrum.

Diseases of a traumatic nature include damage to the auricle due to bruises, the presence of foreign bodies in the auditory canal, deformation of the eardrum, burns, acoustic injuries, and vibration injuries.

There are many reasons why hearing loss can occur. It may occur as a result of a violation of sound perception or sound transmission. In most cases, medicine can restore hearing. Drug therapy, physiotherapy, and surgical treatment are carried out.

Doctors are able to replace the auditory ossicles or eardrum with synthetic ones, and install an electrode in the human inner ear that will transmit vibrations to the brain. But if hair cells are damaged as a result of pathology, then hearing cannot be restored.

The structure of the human ear is complex and the appearance of a negative factor can impair hearing or lead to complete deafness. Therefore, a person must maintain hearing hygiene and prevent the development of infectious diseases.

An important element of the human body are the auditory ossicles. These miniature formations play almost the main role in the process of sound perception. Without them, it is impossible to imagine the transmission of wave vibrations and vibrations, so it is important to protect them from diseases. These bones themselves have an interesting structure. This, as well as the principle of their operation, should be discussed in more detail.

Types of auditory ossicles and their location

In the cavity of the middle ear, sound vibrations are perceived and subsequently transmitted to the internal part of the organ. All this becomes possible thanks to the presence of special bone formations.

The bones are covered with a layer of epithelium, so they do not injure the eardrum.

They are combined into a single group - the auditory ossicles. To understand the principle of their operation, you need to know what these elements are called:

  • hammer;
  • anvil;
  • stapes.

Despite their tiny size, the role of each is simply invaluable. They got their names due to their special shape, resembling a hammer, anvil and stirrup, respectively. Let's look at what exactly each auditory bone serves for next.

As for location, the ossicles are located in the middle ear cavity. By fastening with muscle formations, they adjoin the eardrum and exit into the window of the vestibule. The latter opens the passage from the middle ear to the inner ear.

All three bones form an integral system. They are connected to each other using joints, and their shape ensures perfect joining. The following connections can be distinguished:

  • in the body of the incus there is an articular fossa that connects to the malleus, or more precisely, to its head;
  • the lenticular process on the long stalk of the incus connects to the head of the stapes.
  • the posterior and anterior legs of the stirrup bone are united by its base.

As a result, two articular joints are formed, and the extreme elements are connected to the muscles. The tensor tympani muscle grips the handle of the malleus. With its help it is set in motion. Its antagonist muscle, which connects to the posterior leg of the stapes, regulates pressure on the base of the bone in the window of the vestibule.

Functions performed

Next, you need to find out what role the auditory ossicles play in the process of sound perception. Their adequate operation is necessary for the full transmission of sound signals. At the slightest deviation from the norm, conductive hearing loss occurs.

Two main tasks of these elements should be highlighted:

  • bone conduction of sound waves and vibrations;
  • mechanical transmission of external signals.

When sound waves enter the ear, vibrations of the eardrum occur. This is possible due to muscle contraction and bone movement. To prevent damage to the middle ear cavity, control over the reaction of mobile elements is partially carried out at the reflex level. Muscle contraction keeps the bones from oscillating excessively.

Due to the fact that the handle of the hammer is quite long, when the muscle is tense, a lever effect occurs. As a result, even small sound signals cause an appropriate reaction. The auricular ligament of the malleus, incus and stapes transmits the signal to the vestibule of the inner ear. Further, the leading role in transmitting information belongs to sensors and nerve endings.

Relationship with other elements

The auditory ossicles are closely connected to each other using articular nodes. In addition, they are connected to other elements, forming a continuous chain of the sound transmission system. Communication with previous and subsequent links is carried out using muscles.

The first direction is the eardrum and the muscle that tenses it. A thin membrane forms a ligament due to the process of a muscle connected to the handle of the malleus. Reflex contractions protect the membrane from rupture during sudden loud sounds. However, excessive loads can not only damage such a sensitive membrane, but also displace the bone itself.

The second direction is the exit of the base of the stapes into the oval window. The stapedius muscle holds its pedicle and relieves pressure on the window of the vestibule. It is in this part that the signal is transmitted to the next level. From the ossicles of the middle ear, impulses pass to the inner ear, where the signal is converted and subsequently transmitted along the auditory nerve to the brain.

Thus, the bones act as a connecting link in the system of receiving, transmitting and processing sound information. If the middle ear cavity is subject to changes due to pathologies, injuries or diseases, the functioning of the elements may be impaired. It is important to prevent displacement, blocking and deformation of fragile bones. In some cases, otosurgery and prosthetics come to the rescue.

Auditory ossicles*(ossicula auditiva) - are located in the middle ear cavity of vertebrates and morphologically represent parts of the visceral skeleton (see Vertebrates). Amphibians, reptiles and birds have only one bone, corresponding to the stirrup (stapes) and called columella auris. In mammals, in particular in humans, there are 3 main bones: The malleus (malleus), which consists of a head and a manubrium, bearing two processes, short and long, and tightly connected to the eardrum. A very important muscle (m. laxator tympani), which serves to relieve the tension of the eardrum (see Hearing), is attached to the long process, and another important muscle that strains the membrane (m. tensor tympani) is attached to the short process. The second bone - the anvil (inxus) - really has the shape of an anvil, consisting of a body equipped with two processes: a short one, attached to the eardrum by means of a ligament, and a long one, which at the end is equipped with an apophysis, sometimes considered an independent (so-called lenticular) bone (ossiculum lenticulare Sylvii). Adjacent to this bone is the 3rd bone - the stirrup, and the outer surface of the anvil body has a recess into which the head of the malleus is received. The stirrup (stapes) consists of a head, articulated with the lentil-shaped bone, and two curved arches (crura) extending from the head, limiting the space covered by a special membrane (membrana propria stapidis) and resting on the third component of the stirrup - the footrest, locking the oval labyrinth window. Columella auris is usually a shelf-shaped bone, one end resting on the tympanic membrane and the other on the oval window. In many lower mammals, the stirrup has the same column shape, but in higher ones, instead of a column, we have two knees, between which passes an artery, which, however, only in a few mammals (rodents, insectivores) remains for life, and in the majority, including number in humans, disappears. V. M. Zh.

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The auditory ossicles were formed during the evolution of terrestrial vertebrates from the gill arches of fish. In 1837, German anatomist Karl Reichert studied embryos of mammals and reptiles, trying to understand the process of skull formation.

What role do the auditory ossicles of the middle ear play: purpose and functions

He discovered that the malleus and incus of mammals correspond to fragments of the lower jaw of reptiles - the articular and quadrate bones; this means that the same branchial arch of the embryo that forms the auditory bones in mammals forms part of the jaw in reptiles. However, this discovery was not properly appreciated: it happened at a time when biology was dominated by views on the eternity and immutability of species, and before the publication of “The Origin of Species” by Ch.

Darwin (1859) was more than twenty years away. The connection between the auditory bones of mammals and the lower jaw bone of reptiles was finally established at the end of the 19th and beginning of the 20th centuries. William King Gregory, an employee of the Natural History Museum in New York, studied fossil lizards found in South Africa and Russia. Tracing the changes in their skeleton from early to later forms, he established that the bones of the posterior part of the jaw (articulate and quadrate) gradually shifted and decreased in the process of evolution, until they finally turned into two auditory ossicles of mammals - the malleus and hammer.

In 1910-1912, Ernst Gaupp provided even more evidence of the connection between the jaw bones of reptiles and the auditory ossicles of animals. Thus, the former fragments of the lower jaw of reptiles began to serve their descendants - mammals - for better perception of sounds. The stapes is the most ancient auditory ossicle in origin; it is present in all terrestrial vertebrates (amphibians, reptiles, birds, mammals), emerging in the process of evolution from the second gill arch of fish (for example, in the body of sharks, the stapes (ear column) corresponds to a large cartilage connecting upper jaw with skull).

Having gone through a long path of evolutionary development, the fragment of the upper jaw gradually decreased and became an auditory bone.

Bones of reptiles and birds (Non-Mammalian amniote) and the auditory bones of early mammals derived from them (Early Mammal): yellow - articulated bone (hammer), blue - quadrate bone (incus).

The ear column and stapes are not shown; the angular bone is indicated in pink.

Function

The appearance of auditory ossicles in the first terrestrial vertebrates (amphibians) is associated with the need to amplify sound vibrations traveling to the inner ear: air is a much worse conductor of sound than water.

The system of three articulated bones in mammals allows them to perceive sounds at higher frequencies than other vertebrates.

See also

Sources

The auditory ossicles (ossicula auditus) include the malleus (malleus), incus (incus) and stirrup (stapes) (Fig. 557).


557. Auditory ossicles, right.

1 - articulatio incudomalleolaris;
2 - crus breve incudis;
3 - incus;
4 - crus longum incudis;
5 - articulatio incudostapedia;
6 - steps;
7 - manubrium mallei;
8 - malleus;
9 - processus anterior;
10 - caput mallei.

Hammer.

The malleus has a neck (collum mallei) and a handle (manubrium mallei). The head of the malleus (caput mallei) is connected by the incus-malleus joint (articulatio incudomallearis) to the body of the incus. The handle of the malleus fuses with the tympanic membrane, and the muscle that stretches the tympanic membrane (m. tensor tympani) is attached to the neck of the malleus.

Anvil. The anvil, 6-7 mm long, consists of a body (corpus incudis) and two legs: short (crus breve) and long (crus longum).

The long leg bears a lenticular process (processus lenticularis) and is articulated by the incudostapedia joint with the head of the stapes (articulatio incudostapedia).

Stirrup. The stirrup has a head (caput stapedis), anterior and posterior legs (crura anterius et posterius) and a base (basis stapedis).

The stapedius muscle (m. stapedius) is attached to the posterior leg. The base of the stapes is inserted into the oval window of the vestibule of the labyrinth. The annular ligament (lig. anulare stapedis), in the form of a membrane located between the base of the stapes and the edge of the oval window, ensures the mobility of the stapes when exposed to air waves on the eardrum.

Muscles of the auditory ossicles
Two striated muscles are attached to the auditory ossicles.

1. The muscle that stretches the eardrum (m. tensor tympani) originates from the walls of the muscular-tubal canal of the temporal bone and is attached to the neck of the malleus.

Function. By pulling the handle of the hammer inside the tympanic cavity, it strains the eardrum, so the eardrum is tense and the innervation (V pair of nerves) is concave into the cavity of the middle ear.
2. Stapes muscle (m.

Auditory ossicles

stapedius) begins in the thickness of the pyramidal eminence of the mastoid wall of the tympanic cavity and is attached to the posterior leg of the stapes.

Function. Contracting, it removes the base of the stapes from the hole (innervation of the VII pair of nerves). With strong vibrations of the auditory ossicles, together with the previous muscle, it holds the auditory ossicles, reducing their displacement.

The auditory ossicles, connected by joints, and the muscles of the middle ear provide air vibrations of varying intensity.

Which sequence of auditory ossicles correctly reflects the transmission of sound? vibrations from the tympanic membrane of the outer ear to the oval window of the inner ear

Answers:

Anatomically, the ear is divided into three parts: the outer, middle and inner ear. Outer ear. The protruding part of the outer ear is called the auricle; it is based on semi-rigid supporting tissue - cartilage. The opening of the external auditory canal is located in the front of the auricle, and the passage itself is directed inward and slightly forward.

The auricle concentrates sound vibrations and directs them to the external auditory opening. The middle ear is a whole complex - including the tympanic cavity and the auditory (Eustachian) tube, k.t.

The auditory ossicles* are

refers to a sound-conducting apparatus. A thin, flat membrane called the eardrum separates the inner end of the external auditory canal from the tympanic cavity, a flattened, rectangular space filled with air. In this cavity of the middle ear there is a chain of three movably articulated miniature bones (ossicles), which transmit vibrations from the eardrum to the inner ear.

According to their shape, the bones are called the malleus, incus and stirrup. Inner ear. The bony cavity of the inner ear, containing a large number of chambers and passages between them, is called the labyrinth. It consists of two parts: the bony labyrinth and the membranous labyrinth.

The bony labyrinth is a series of cavities located in the dense part of the temporal bone; there are three components in it: the semicircular canals are one of the sources of nerve impulses that reflect the position of the body in space; vestibule; and the cochlea - the organ of hearing. The membranous labyrinth is enclosed within the bony labyrinth. It is filled with a fluid, endolymph, and is surrounded by another fluid, perilymph, which separates it from the bony labyrinth. The membranous labyrinth, like the bony labyrinth, consists of three main parts.

The first corresponds in configuration to the three semicircular canals. The second divides the bony vestibule into two sections: the utricle and the sac. The elongated third part forms the middle (cochlear) scala (spiral canal), repeating the bends of the cochlea.

6.3.3. Structure and functions of the middle ear

Middle ear(Fig. 51) is represented by a system of air cavities in the thickness of the temporal bone and consists of tympanic cavity, auditory tube And mastoid process with its bone cells.

Tympanic cavity- The central part of the middle ear, located between the eardrum and the inner ear, is lined with mucous membrane on the inside and filled with air.

In shape it resembles an irregular tetrahedral prism, with a volume of about 1 cm3. The upper wall or roof of the tympanic cavity separates it from the cranial cavity. There are two openings in the inner bony wall that separates the middle ear from the inner ear: oval And round windows covered with elastic membranes.

The auditory ossicles are located in the tympanic cavity: hammer, anvil and stirrup(so called due to their shape), which are interconnected by joints, strengthened by ligaments and represent a system of levers.

The handle of the malleus is woven into the center of the eardrum, its head articulates with the body of the incus, and the incus, in turn, articulates with the head of the stapes through a long process. The base of the stirrup goes into oval window(as in a frame), connecting to the edge through a ring connection of the stirrup.

The outside of the bones is covered with a mucous membrane.

Function auditory ossicles - transmission of sound vibrations from the tympanic membrane to the oval window of the vestibule and their gain, which allows you to overcome the resistance of the oval window membrane and transmit vibrations to the perilymph of the inner ear. This is facilitated by the lever method of articulation of the auditory ossicles, as well as the difference in the area of ​​the tympanic membrane (70 - 90 mm2) and the area of ​​the membrane of the oval window (3.2 mm2).

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 pressure-increasing mechanism is an extremely useful device aimed at ensuring efficient transmission of acoustic energy from the air environment of the middle ear into the fluid-filled cavity of the inner ear. Therefore, even weak sound waves can cause an auditory sensation.

What are the auditory ossicles used for?

In the middle ear there are two muscles(the smallest muscles in the body), attached to the handle of the malleus (tensor tympani muscle) and the head of the stapes (stapedius muscle), they support the auditory ossicles, regulate their movements, providing accommodation of the hearing aid to sounds of different strengths and heights.

For the normal functioning of the eardrum and the chain of auditory ossicles, it is necessary that air pressure on either side of the eardrum(in the external auditory canal and tympanic cavity) was the same. This function is performed auditory(Eustachian) pipe- a canal (about 3.5 cm long, about 2 mm wide) connecting the tympanic cavity of the middle ear with the cavity of the nasopharynx (Fig.

51). From the inside, it is lined with a mucous membrane with ciliated epithelium, the movement of the cilia is directed towards the nasopharynx. The part of the pipe adjacent to the tympanic cavity has bone walls, and the part of the pipe adjacent to the nasopharynx has cartilaginous walls, which usually touch each other, but when swallowing, yawning, due to the contraction of the pharyngeal muscles, they diverge to the sides and air enters from the nasopharynx into the tympanic cavity. This maintains equal air pressure on the eardrum from the external auditory canal and the tympanic cavity.

Mastoid– a process of the temporal bone (shaped like a nipple), located behind the auricle. In the thickness of the process there are cavities - cells filled with air and communicating with each other through narrow cracks.

They improve the acoustic properties of the middle ear.


Rice. 51. Structure of the middle ear:

4 – hammer, 5 – anvil, 6 – stirrup; 7 – auditory tube

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).


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 stirrup is the final link in the chain of auditory ossicles. On the inside of the tympanic cavity there are 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 stirrup 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 by the 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 at the VII International Congress of 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 the inner surface of the mastoid process, which faces the posterior cranial fossa, there is a grooved depression in which the sigmoid sinus is located, which drains venous blood from the brain into 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.

Auditory ossicles* (ossicula auditiva) - are located in the middle ear cavity of vertebrates and morphologically represent parts of the visceral skeleton (see Vertebrates). Amphibians, reptiles and birds have only one bone, corresponding to the stirrup (stapes) and called columella auris. In mammals, in particular in humans, there are 3 main bones: The malleus (malleus), which consists of a head and a manubrium, bearing two processes, short and long, and tightly connected to the eardrum.

A very important muscle (m. laxator tympani), which serves to weaken the tension of the eardrum (see Hearing), is attached to the long process, and another important muscle that strains the membrane (m. tensor tympani) is attached to the short process. The second bone - the incus (inxus) - really has the shape of an anvil, consisting of a body equipped with two processes: a short one, attached to the eardrum by means of a ligament, and a long one, which is equipped at the end with an apophysis, sometimes considered independent (the so-called lenticular) bone (ossiculum lenticulare Sylvii). Adjacent to this bone is the 3rd bone - the stirrup, and the outer surface of the anvil body has a recess into which the head of the malleus is received. The stirrup (stapes) consists of a head, articulated with the lentil-shaped bone, and two curved arches (crura) extending from the head, limiting the space covered by a special membrane (membrana propria stapidis) and resting on the third component of the stirrup - the footrest, locking the oval labyrinth window. Columella auris is usually a shelf-shaped bone, one end resting on the tympanic membrane and the other on the oval window. In many lower mammals, the stirrup has the same column shape, but in higher ones, instead of a column, we have two knees, between which passes an artery, which, however, only in a few mammals (rodents, insectivores) remains for life, and in the majority, including number in humans, disappears.

Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron. - S.-Pb.: Brockhaus-Efron. 1890-1907 .

See what “Auditory ossicles*” are in other dictionaries:

    AUDITORY BONES, a complex of small bones in the middle EAR of most mammals. The auditory ossicles are the malleus, incus and stapes. Vibrations of the eardrum (in the tympanic cavity) are captured by the hammer and amplified... ... Scientific and technical encyclopedic dictionary

    AUDITORY BONES- See bones, auditory...

    - (ossicula auditiva) are located in the middle ear cavity of vertebrates and morphologically represent parts of the visceral skeleton (see Vertebrates). Amphibians, reptiles and birds have only one bone, corresponding to the stirrup (stapes) and called... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron

    Auditory ossicles- Three miniature bones of the middle ear: the malleus, the incus and the stapes, which are involved in transmitting sound pressure to the inner ear... Psychology of sensations: glossary

    Auditory ossicles (ossicula auditis), right- hammer; hammer head; incus malleus joint; anvil; short anvil leg; long anvil leg; incus of the stirrup joint; stirrup; posterior leg of the stirrup; base of the stirrup; anterior leg of the stirrup; handle... ... Atlas of Human Anatomy

    - (ossicula auditus, PNA, BNA; ossicula tympani, JNA) see List of anat. terms... Large medical dictionary

    BONES, AUDITORY- A set of three small bones (malleus, incus and stirrup) in the middle ear, which transmit vibrations of the tympanum to the cochlea... Explanatory dictionary of psychology

    Middle ear- (auris media) (Fig. 287), which is also called the tympanic cavity (cavum tympani), is a sound-conducting system that includes several components. The eardrum (membrana tympani) (Fig. 287, 288) is located on... ... Atlas of Human Anatomy

    MIDDLE EAR- MIDDLE EAR. Phylogenesis. In the historical development of the hearing aid, at a certain stage the auxiliary, so-called inner ear begins to join the more ancient formation of the inner ear. sound-conducting section, the deeper part of the horn is C... Great Medical Encyclopedia

    - (aurus media) part of the ear between the outer and inner ear, performing a sound-conducting function. The middle ear is located in the temporal bone and consists of three interconnected air cavities. The main cavity is the tympanic cavity (cavum... ... Medical encyclopedia