There are three auditory ossicles. Structure of the hearing organ

The middle ear is a component of the ear. It occupies the space between the external auditory organ and the tympanic membrane. Its structure involves numerous elements that have certain features and functions.

Structural features

The middle ear consists of several important elements. Each of these components has structural features.

Tympanic cavity

This is the middle part of the ear, very vulnerable, often subjected to inflammatory diseases. It is located behind the eardrum, not reaching the inner ear. Its surface is covered with a thin mucous membrane. It has the shape of a prism with four irregular sides, filled with air inside. Consists of several walls:

• The outer wall with a membranous structure is formed by the inner part of the tympanic membrane, as well as the bone of the ear canal.
• The inner wall on top has a recess in which the window of the vestibule is located. It is a small oval hole, which is covered by the bottom surface of the stirrup. Below it there is a cape along which a furrow runs. Behind it is a funnel-shaped dimple in which the cochlear window is placed. From above it is limited by a bone ridge. Above the window of the cochlea there is a tympanic sinus, which is a small depression.
• The upper wall, which is called the tegmental, as it is formed by a solid bone substance and protects it. The deepest part of the cavity is called the dome. This wall is necessary to separate the tympanic cavity from the walls of the skull.
• The lower wall is jugular, as it participates in the creation of the jugular fossa. It has an uneven surface, as it contains drum cells necessary for air circulation.
• The posterior mastoid wall contains an opening that leads to the mastoid cave.
• The anterior wall has a bone structure and is formed by a substance from the canal of the carotid artery. Therefore, this wall is called the carotid wall.

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

auditory ossicles

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

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

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

• The hammer has a rounded head connected to the handle.
• The anvil has a rather massive body, as well as 2 processes. One of them is short, rests against the hole, and the second is long, directed towards the handle of the hammer, thickened at the end.
• The stirrup includes a small head, covered on top articular cartilage, serves to articulate the anvil and 2 legs - one straight, and the second more curved. These legs are attached to the oval plate contained in the fenestra vestibule.

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

muscles

The middle ear also has 2 muscles - they are the smallest in the human body. The muscle bellies are located in the secondary cavities. One serves to tension the eardrum and is attached to the handle of the hammer. The second is called the stirrup and is attached to the head of the stapes.

These muscles are necessary to maintain the position of the auditory ossicles and regulate their movements. This provides the ability to perceive sounds of varying strengths.

Eustachian tube

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

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

Due to its close proximity to the nasopharynx, the Eustachian tube is susceptible to inflammatory processes, since the infection can easily enter it from the nose. Its patency may be impaired due to colds.

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

• Examine the ear. Unpleasant symptom can be called ear plug. You can remove it yourself. To do this, drop a few drops of peroxide into the ear canal. After 10-15 minutes, the sulfur will soften, so it can be easily removed.
• Move your lower jaw. This method helps with mild congestion. It is necessary to push the lower jaw forward and move it from side to side.
• Apply the Valsalva technique. Suitable in cases where ear congestion does not go away for a long time. It is necessary to close your ears and nostrils and take a deep breath. You should try to exhale it with your nose closed. The procedure should be carried out very carefully, as during it the arterial pressure and increase your heart rate.
• Use Toynbee's method. You need to fill your mouth with water, close your ears and nostrils, and take a sip.

The Eustachian tube is very important because it maintains normal pressure in the ear. And when it is blocked for various reasons, this pressure is disrupted, the patient complains of tinnitus.

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

Mastoid

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

Main functions

The following functions of the middle ear can be distinguished:

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

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

Middle ear, auris mebia , includes a mucous membrane-lined and air-filled tympanic cavity (about 1 cm3 in volume) and an auditory (Eustachian) tube. The middle ear cavity communicates with the mastoid cave and through it with the mastoid cells located in the thickness of the mastoid process.

tympanic cavity,cdvitas tympani [ cavitas tympanicaj, located in the thickness of the pyramid of the temporal bone, between the external auditory canal laterally and the bony labyrinth of the inner ear medially. The tympanic cavity, in which 6 walls are distinguished, is compared in shape with a tambourine placed on its edge and tilted outward.

1. Upper tegmental wall,paries tagmentlis, formed by a thin plate of bone substance (tegmen tympani), separating the tympanic cavity from the cranial cavity. 2. Bottom jugular wall,paries juguldris, corresponds to the lower wall of the pyramid in the place where the jugular fossa is located. 3. Medial labyrinth wall,paries labyrinthicus, complex, separates the tympanic cavity from the bony labyrinth of the inner ear. On this wall there is a protruding towards the tympanic cavity cape,promontorium. Above the promontory and somewhat posteriorly there is an oval vestibule window,fenestra vestii- buli, leading to the vestibule of the bony labyrinth; it is covered by the base of the stirrup. Somewhat above the oval window and behind it there is a transverse facial canal projection(channel walls facial nerve), prominentia candlis facidlis. Behind and below the cape is snail window,fenestra cochleae, closed secondary tympanic membrane,membrdna tympani secundd- ria, separating the tympanic cavity from the scala tympani. 4. Rear mastoid wall,paries mastoideus, at the bottom has pyramidal elevation,eminentia pyramidlis, inside which it begins stapedius muscle,m. stapedius. In the upper part of the posterior wall, the tympanic cavity continues into mastoid cave,dntrum mastoideum, into which the mastoid cells of the process of the same name also open. 5. Front sleepy wall,paries cardticus, in its lower part it separates the tympanic cavity from the carotid canal, in which the internal carotid artery passes. In the upper part of the wall there is an opening of the auditory tube, which connects the tympanic cavity with the nasopharynx. 6. Lateral membranous wallparies membrandceus, formed by the eardrum and the surrounding parts of the temporal bone.

In the tympanic cavity there are three auditory ossicles covered with mucous membrane, as well as ligaments and muscles.

auditory ossicles,ossicula auditus [ auditorium], miniature in size, connecting with each other, they form a chain that continues from the eardrum to the end of the vestibule, which opens into the inner ear. In accordance with their shape, the bones received names: hammer, anvil, stirrup (Fig. 211). Hammer, malleus, has a rounded head,cdput mallei, which turns into a long one hammer handle,manubrium mallei, with two processes: lateral and anterior,processus laterlis et anterior. Anvil, incus, consists of a body corpus incudis, with an articular fossa for articulation with the head of the malleus and two legs: one short leg,crus breve, another - long,crus longum, with a thickening at the end. This thickening is lenticular process,pro­ cessus lenticuldris, for connection to the head of the stirrup. S t r e m, stages, has a head cdput stapedis, two legs - front and back,crus anterius el crus posterius, connected by base of the stirrup,basis stapedis, inserted into the window of the vestibule. The hammer, with its handle, is fused along its entire length with the eardrum so that the end of the handle corresponds to the navel on the outer side of the eardrum. The head of the malleus is connected to the body of the incus by means of a joint and forms incus-malleus joint,articulatio in- cudomallearls, and the anvil, in turn, connects with the head of the stapes with its lenticular process, forming incus-stapedial joint,articulatio incudostapedia [ incudo- stapedialisj. The joints are strengthened by miniature ligaments.

With the help of a chain movable in the joints, consisting of three auditory ossicles, vibrations of the eardrum, resulting from the impact of a sound wave on it, are transmitted to the window of the vestibule, in which the base of the stapes is movably fixed with the help of annular ligament of the stapes,lig. anuldre stapedius [ stapediale]. Two muscles attached to the auditory ossicles regulate the movements of the ossicles and protect them from excessive vibrations during strong sounds. The tensor tympani musclem. tensor tympani, lies in the semicanal of the same name of the muscular-tubal canal, and its thin and long tendon is attached to the initial part of the handle of the malleus. This muscle, pulling the handle of the hammer, strains the eardrum. stapedius muscle,m. stapedius, starting in the pyramidal eminence, it is attached by a thin tendon to the posterior leg of the stirrup, near its head. When the stapedius muscle contracts, the pressure of the base of the stapes inserted into the window of the vestibule is weakened.

Auditory (Eustachian) tube,tuba auditiva [ auditorial, with an average length of 35 mm and a width of 2 mm, it serves to bring air from the pharynx into the tympanic cavity and maintain pressure in the cavity equal to the external one, which is important for the normal operation of the sound-conducting apparatus (tympanic membrane and auditory ossicles). The auditory tube consists of bone part,pars ossea, And cartilaginous part(elastic cartilage), pars cartilaginea. Clearance of the pipe at the junction - isthmus of the auditory tube,isthmus tubae auditivae / auditoriaej, tapers to 1 mm. The upper bony part of the tube is located in the hemicanal of the same name of the muscular-tubal canal of the temporal bone and opens on the anterior wall of the tympanic cavity tympanic opening of the auditory tube,ostium tympanicum tubae auditivae [ auditoriaej. The lower cartilaginous part, which accounts for 2 /z the length of the tube, has the appearance of a groove, open at the bottom, formed by the medial and lateral cartilaginous plates and the membranous plate connecting them. At the point where the auditory tube opens on the side wall of the nasopharynx pharyngeal opening of the auditory tube,ostium pharyngeum tubae auditivae /" auditor iaeJ, the medial (posterior) plate of the elastic cartilage of the tube thickens and protrudes into the pharyngeal cavity in the form roller,torus tubdrius. The longitudinal axis of the auditory tube from its pharyngeal opening is directed upward and laterally, forming an angle of 40-45° with the horizontal and sagittal planes.

The tensor muscle and the levator palatine muscle originate from the cartilaginous part of the auditory tube. When they contract, the cartilage of the tube and its membranous plate,lamina membrandcea, are retracted, the pipe channel expands and air from the pharynx enters the tympanic cavity. The mucous membrane of the tube forms longitudinal folds and is covered with ciliated epithelium, the movements of the cilia are directed towards the pharynx. The mucous membrane of the auditory tube contains many mucous glands, gldndulae tubdriae, lymphoid tissue, which forms a cluster near the tubal ridge and around the pharyngeal opening of the auditory tube - the tubal tonsil (see “Organs of hematopoiesis and the immune system”)

The three tiny bones of the middle ear - the malleus, the incus and the stapes - have long attracted the attention of paleontologists, because the formation of this structure is associated with the evolution of the most ancient mammals.

And now, the authors of a new article on the PNAS journal website report yet another remarkable discovery. The first is three completely preserved right auditory ossicles (extracted from the fragmentary skull SKW 18, Swartkrans, age 1.8 million years). The uniqueness of the find can be appreciated if we consider that until now only two cases of preservation of all three bones were known for fossil hominids - and both times this (child La Ferrassie and teenager Le Moustier 2...). It is interesting that, as stated in the appendix to the article, the left stapes from this skull is also present, the bone can be seen in the cavity of the middle ear, but it is walled up there, and no attempts have been made to remove it yet.

Comment from the Scientific Editor of ANTHROPOGENES.RU: In fact, these bones are well preserved; they are also protected by the temporal bone. Only usually they are lost when the skull is cleaned from the ground. Apparently, they decided to clean it carefully once. For the first time not with a screwdriver! They invented a super-brush made from Mexican jerboa wool to clean the ears of australopithecines!

The second find is the left malleus and part of the right stapes (fragment of the skull Stw 255 from Sterkfontein, 2.0-2.5 million years ago).

What are the results? (for those who are not fans of anatomical details - that is, all normal people :) - you can skip this part of the text and go straight to the conclusions).

Hammer

The main feature of the malleus of the middle ear modern man, in comparison with apes - shortening and thickening of the “handle” and the accompanying lengthening of the body (head). This change in shape in the process of evolution was combined with a decrease in the size of the eardrum.

The authors of the article describe in detail the morphology of this bone in two early hominids, point out some differences between them (the shape of the handle and head, the presence of an anterior process in Africanus and its absence in Robustus, etc.), but make the main conclusion: in all major dimensions, both malleus of early hominids are extremely similar to humans. At the same time, Africanus is more human, and the robustus hammer still has some specific features. Logically!

Anvil

A distinctive feature of the anvil of modern humans is the larger size of the long process and the larger angle between the long and short processes, in comparison with other anthropoids.

Unfortunately, the anvil of Africanus was not found, so the researchers are only considering Paranthropus. The authors draw attention to the fact that even in the existing two finds, variations in morphology are visible - for example, a depression along the lower edge of the short process is present in SKW 18, but is absent in SK 848. And here there is a certain specialization of the paranthropus - the articular facet is oriented differently than in humans and in apes (although there are variations here too), the body of the anvil has a peculiar “swollen” shape. In general, in terms of its metric characteristics, the anvil of Paranthropus is primitive, and is closest to the chimpanzee.

Stapes

Unlike the malleus and incus, the stapes of apes and humans differ little in structure. The difference between them is only in size: in humans the stirrup is larger.

Small stirrup sizesP. robustus AndA. africanus bring them closer to apes.

Conclusions:

• Despite some differences, in general the auditory ossicles of the two hominids are similar to each other.
• Hammer P. robustus And A. africanus similar to human. Probably, it was already such in the common ancestor of the hominids in question. How long ago did the hammer take on a human form? To find out, you need some kind of auditory ossicles.
• On the contrary, in the structure of the anvil of Paranthropus we see features characteristic of apes. Unfortunately, nothing can be said about Africanus...
• Stapes P. robustus And A. africanus small, like a monkey's.

In modern primates, the length of the malleus and incus, as well as the area of ​​the oval plate of the stapes, are important characteristics that influence the sensitivity of hearing. Apparently, thanks to the combination of a “human” hammer and a “monkey” anvil, Paranthropus’s hearing had some intermediate, “ape-human” features.

In conclusion, the authors point out that in most primates (except humans!) there is some loss of sensitivity to sounds at medium frequencies, and this feature of hearing is associated with the functional length of the incus. According to this characteristic, Paranthropus's hearing apparently differed from that of humans. The authors leave the conversation about other intricacies of Australopithecus hearing for the future...

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 reception, transmission 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 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 outside surface the body of the incus 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. - St. Petersburg: 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. 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