Table of contents of the topic "Anatomy of the ear":
1. Vestibulocochlear organ, organum vestibulocochleare. The structure of the balance organ (pre-cochlear organ).
2. Embryogenesis of the organ of hearing and gravity (balance) in humans.
3. External ear, auris externa. Auricle, auricula. External auditory canal, meatus acusticus externus.
4. Eardrum, membrana tympani. Vessels and nerves of the external ear. Blood supply to the external ear.
5. Middle ear, auris media. Tympanic cavity, cavitas tympanica. Walls of the tympanic cavity.
6.
7. Muscle tensor tympani, m. tensor tympani. Stapedius muscle, m. stapedius Functions of the muscles of the middle ear.
8. Auditory tube, or Eustachian tube, tuba auditiva. Vessels and nerves of the middle ear. Blood supply to the middle ear.
9. Inner ear, labyrinth. Bone labyrinth, labyrinthus osseus. vestibule, vestibulum.
10. Bone semicircular canals, canales semicirculares ossei. Snail, cochlea.
11. Membranous labyrinth, labyrinthus membranaceus.
12. Structure of the auditory analyzer. Spiral organ, organon spirale. Helmholtz's theory.
13. Vessels of the inner ear (labyrinth). Blood supply to the inner ear (labyrinth).

Auditory ossicles: Hammer, malleus; Anvil, incus; Stirrup, stapes. Functions of the bones.

Located in tympanic cavity three small auditory ossicles Based on their appearance, they are called the malleus, incus and stirrup.

1. malleus, malleus, equipped with a rounded head, caput mallei, which through cervix, collum mallei, connects with handle, manubrium mallei.

2. Anvil, incus, has a body, corpus incudis, and two diverging processes, one of which is more short, crus breve, directed backwards and rests on the hole, and the other - long shoot, crus longum, runs parallel to the handle of the malleus medially and posteriorly from it and at its end has a small oval thickening, processus lenticularis, articulated with the stirrup.

3. Stirrup, stapes, in its form justifies its name and consists of small head, caput stapedis, bearing the articular surface for processus lenticularis anvil and two legs: anterior, more straight, crus anterius, and back, more curved, crus posterius, which connect with oval plate, basis stapedis, inserted into the window of the vestibule.
At the junctions of the auditory ossicles, two true joints with limited mobility: articulatio incudomallearis and articulatio incudostapedia. The stirrup plate is connected to the edges fenestra vestibuli through connective tissue, syndesmosis tympano-stapedia.

Auditory ossicles strengthened, in addition, by several more separate ligaments. Generally all three auditory ossicles represent a more or less mobile chain running across the tympanic cavity from the eardrum to the labyrinth. Ossicular mobility gradually decreases in the direction from the malleus to the stapes, which protects the spiral organ located in the inner ear from excessive shocks and sharp sounds.

The chain of ossicles performs two functions:
1) bone conduction of sound and
2) mechanical transmission of sound vibrations to the oval window of the vestibule, fenestra vestibuli.

The middle ear is a component of the ear. Occupies the space between the external auditory organ and the eardrum. 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 subject 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 faces and is filled with air inside. Consists of several walls:

• The outer wall with a membranous structure is formed by the inner part of the eardrum as well as the bone of the ear canal.
• The inner wall at the top has a recess in which the window of the vestibule is located. It is a small oval hole, which is covered by the lower surface of the stapes. 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 wall, as it is formed by hard 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 because it contains drum cells necessary for air circulation.
• The posterior mastoid wall contains an opening that leads into the mastoid cave.
• The anterior wall has a bone structure and is formed by substance from the carotid artery canal. 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 area 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 with articular cartilage, which serves to articulate the incus and 2 legs - one straight and the other 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 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. An unpleasant symptom may be caused by an 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 blood pressure may change and the heartbeat may accelerate.
• 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

This is a small bone formation, convex above the surface and shaped like a papilla. Located behind the ear. 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, various diseases may appear that lead to hearing impairment.

One of the complex organs of the human structure that performs the function of perceiving sounds and noise is the ear. In addition to its sound-conducting purpose, it is responsible for the ability to control the stability and location of the body in space.

The ear is located in the temporal region of the head. Externally it looks like an auricle. have serious consequences and pose a threat to general health.

The structure of the ear has several compartments:

• external;
• average;
• internal.

Human ear– an exceptional and intricately designed organ. However, the method of functioning and performance of this organ is simple.

Ear function is to distinguish and enhance signals, intonations, tones and noise.

There is a whole science dedicated to the study of the anatomy of the ear and its many indicators.

It is impossible to visualize the entire functioning of the ear, since the auditory canal is located in the inner part of the head.

For efficient execution The main function of the human middle ear is the ability to hear - The following components are responsible:

1. Outer ear. It looks like the auricle and ear canal. Separated from the middle ear by the eardrum;
2. The cavity behind the eardrum is called middle ear. It includes the ear cavity, the auditory ossicles and the Eustachian tube;
3. The last of the three types of department is inner ear. It is considered one of the most complex parts of the hearing organ. Responsible for human balance. Because of the peculiar shape of the structure it is called “ labyrinth».

The anatomy of the ear includes: structural elements, How:

1. Curl;
2. Anti-curl– a paired organ of the tragus, located on top of the earlobe;
3. Tragus, which is a bulge on the outer ear, is located on the front of the ear;
4. Antitragus in the image and likeness it performs the same functions as the tragus. But first of all it processes sounds coming from the front;
5. Earlobe.

Thanks to this structure of the ear, the influence of external circumstances is minimized.

Structure of the middle ear

The middle ear is represented as a tympanic cavity, located in the temporal region of the skull.

In the depths of the temporal bone are located the following elements of the middle ear:

1. Tympanic cavity. It is located between the temporal bone and the external auditory canal and inner ear. Consists of the small bones listed below.
2. Eustachian tube. This organ connects the nose and pharynx with the tympanic region.
3. Mastoid. This is part of the temporal bone. Located behind the external auditory canal. Connects the scales and the tympanic part of the temporal bone.

IN structure tympanic area of ​​the ear included:

• Hammer. It is adjacent to the eardrum and sends sound waves to the incus and stapes.
• Anvil. Located between the stirrup and the malleus. The function of this organ is to represent sounds and vibrations from the malleus to the stapes.
• Stapes. The incus and inner ear are connected by the stapes. Interestingly, this organ is considered the smallest and lightest bone in humans. Her size amounts to 4 mm, and weight – 2.5 mg.

The listed anatomical elements bear the following function auditory ossicles – transformation of noise and transmission from the external canal to the inner ear.

Malfunction of one of the structures leads to destruction of the function of the entire organ of hearing.

The middle ear is connected to the nasopharynx by Eustachian tube.

Function Eustachian tube - regulation of pressure that does not come from air.

A sharp ear plug signals a rapid decrease or increase in air pressure.

Long and painful pain in the temples indicates that a person’s ears are currently actively fighting the emerging infection and protecting the brain from impaired performance.

In number interesting facts pressure also includes reflex yawning. This indicates that there has been a change in the ambient pressure, which causes the person to react in the form of a yawn.

The human middle ear has a mucous membrane.

Structure and function of the ear

It is known that the middle ear contains some of the main components of the ear, the violation of which will lead to hearing loss. Since there are important details in the structure, without which the conduction of sounds is impossible.

Auditory ossicles– the malleus, incus and stapes ensure the passage of sounds and noises further along the structure of the ear. In their tasks includes:

• Allow the eardrum to function smoothly;
• Do not allow sharp and strong sounds to pass into the inner ear;
• Adapt the hearing aid to different sounds, their strength and height.

Based on the listed tasks, it becomes clear that Without the middle ear, the function of the hearing organ is unrealistic.

Remember that sharp and unexpected sounds can provoke reflex muscle contraction and harm the structure and functioning of hearing.

Measures to protect against ear diseases

In order to protect yourself from ear diseases, it is important to monitor your health and listen to your body’s symptoms. Recognize infectious diseases such as others promptly.

The main source of all diseases in the ear and other human organs is weakened immunity. To reduce the possibility of illness, take vitamins.

In addition, you should isolate yourself from drafts and hypothermia. Wear a hat in cold seasons, and do not forget to put a cap on your child, regardless of the temperature outside.

Do not forget to undergo an annual examination of all organs, including an ENT specialist. Regular visits to the doctor will help prevent inflammation and infectious diseases.

Anyone who looks deeper into the ear to see how our hearing organ works will be disappointed. The most interesting structures of this apparatus are hidden deep inside the skull, behind the bone wall. You can get to these structures only by opening the skull, removing the brain, and then also breaking open the bone wall itself. If you are lucky or if you know how to do it masterfully, then an amazing structure will appear before your eyes - the inner ear. At first glance, it resembles a small snail, like the ones you might find in a pond.

It may look unassuming, but upon closer examination it turns out to be a very complex device, reminiscent of the most ingenious human inventions. When sounds reach us, they enter the funnel of the auricle (which we usually call the ear). Through the external auditory canal they reach the eardrum and cause it to vibrate. The eardrum is connected to three miniature bones that vibrate behind it. One of these bones is connected by something like a piston to a snail-like structure. The vibration of the eardrum causes this piston to move back and forth. As a result, a special jelly-like substance moves back and forth inside the snail. The movements of this substance are perceived by nerve cells, which send signals to the brain, and the brain interprets these signals as sound. The next time you listen to music, just imagine all the pandemonium that is happening in your head.

This entire system has three parts: the outer, middle and inner ear. The outer ear is that part of the hearing organ that is visible from the outside. The middle ear is made up of three miniature bones. Finally, the inner ear is made up of sensory nerve cells, a jelly-like substance, and the tissues that surround them. By considering these three components separately, we can understand our hearing organs, their origin and development.

Our ear consists of three parts: the outer, middle and inner ear. The oldest of them is the inner ear. It controls nerve impulses sent from the ear to the brain.

The auricle, which we usually call the ear, was given to our ancestors in the course of evolution relatively recently. You can verify this by visiting a zoo or aquarium. Which sharks, bony fishes, amphibians and reptiles have ears? This structure is characteristic only of mammals. In some amphibians and reptiles, the outer ear is clearly visible, but they do not have an auricle, and the outer ear usually looks like a membrane, like the one stretched over a drum.

The subtle and deep connection that exists between us and fish (both cartilaginous, sharks and rays, and bony ones) will only be revealed to us when we consider the structures located deep in the ears. At first glance, it may seem strange to look for connections between humans and sharks in the ears, especially since sharks do not have them. But they are there, and we will find them. Let's start with the auditory ossicles.

Middle ear - three auditory ossicles

Mammals are special creatures. Hair and mammary glands distinguish us mammals from all other living organisms. But many may be surprised to learn that the structures located deep in the ear are also important distinguishing features of mammals. No other animal has bones like those in our middle ear: mammals have three of these bones, while amphibians and reptiles have only one. But fish don’t have these bones at all. How then did the bones of our middle ear arise?

A little anatomy: let me remind you that these three bones are called the malleus, incus and stirrup. As already mentioned, they develop from the gill arches: the malleus and incus from the first arch, and the stapes from the second. This is where our story begins.

In 1837, German anatomist Karl Reichert studied embryos of mammals and reptiles to understand how the skull is formed. He traced the development of gill arch structures in different species to understand where they end up in the skulls of different animals. The result of lengthy research was a very strange conclusion: two of the three auditory ossicles of mammals correspond to fragments of the lower jaw of reptiles. Reichert couldn't believe his eyes! Describing this discovery in his monograph, he did not hide his surprise and delight. When he comes to compare the auditory ossicles and jaw bones, the usual dry style of 19th-century anatomical descriptions gives way to a much more emotional style, showing how amazed Reichert was by this discovery. From the results he obtained, an inevitable conclusion followed: the same gill arch that forms part of the jaw in reptiles forms the auditory ossicles in mammals. Reichert put forward the thesis, which he himself found difficult to believe, that the structures of the middle ear of mammals correspond to the structures of the jaw of reptiles. The situation will look more complicated if we remember that Reichert came to this conclusion more than twenty years earlier than Darwin’s position about a single family tree of all living things was announced (this happened in 1859). What is the point of saying that different structures in two different groups of animals "correspond" to each other, without a concept of evolution?

Much later, in 1910 and 1912, another German anatomist, Ernst Gaupp, continued Reichert's work and published the results of his exhaustive studies on the embryology of the mammalian hearing organs. Gaupp provided more details, and, given the time in which he worked, was able to interpret Reichert's discovery within the framework of ideas about evolution. Here are the conclusions he came to: the three bones of the middle ear demonstrate a connection between reptiles and mammals. The single ossicle of the middle ear of reptiles corresponds to the stapes of mammals - both develop from the second branchial arch. But the truly stunning discovery was not this, but the fact that the other two bones of the mammalian middle ear - the malleus and the incus - developed from ossicles located at the back of the jaw in reptiles. If this is true, then the fossils should show how the ossicles passed from the jaw to the middle ear during the rise of mammals. But Gaupp, unfortunately, studied only modern animals and was not ready to fully appreciate the role that fossils could play in his theory.

Since the forties of the 19th century, fossil remains of animals of a previously unknown group began to be mined in South Africa and Russia. Many well-preserved finds were discovered - entire skeletons of creatures the size of a dog. Soon after these skeletons were discovered, many of their specimens were packed into boxes and sent to Richard Owen in London for identification and study. Owen discovered that these creatures had a striking mixture of characteristics from different animals. Some of their skeletal structures resembled reptiles. At the same time, others, especially the teeth, were more like those of mammals. Moreover, these were not just isolated finds. In many localities, these mammal-like reptiles were the most abundant fossils. They were not only numerous, but also quite diverse. After Owen's research, such reptiles were discovered in other areas of the Earth, in several layers of rocks corresponding to different periods of earth's history. These finds formed an excellent transitional series leading from reptiles to mammals.

Until 1913, embryologists and paleontologists worked in isolation from each other. But this year was significant in that the American paleontologist William King Gregory, an employee of the American Museum of Natural History in New York, drew attention to the connection between the embryos that Gaupp studied and fossils discovered in Africa. The most "reptilian" of all mammal-like reptiles had only one bone in the middle ear, and its jaw, like other reptiles, consisted of several bones. But as Gregory studied a series of increasingly mammalian-like reptiles, Gregory discovered something quite remarkable—something that would have deeply astonished Reichert had he lived: a successive series of shapes that clearly showed that the bones of the back of the jaw in mammal-like reptiles were gradually decreased and shifted until, finally, in their descendants, mammals, they took their place in the middle ear. The malleus and incus actually developed from the jaw bones! What Reichert discovered in embryos had long ago lain in the ground in fossil form, awaiting its discoverer.

Why did mammals need to have three bones in the middle ear? The system of these three bones allows us to hear sounds of a higher frequency than those animals that have only one bone in the middle ear are able to hear. The emergence of mammals was associated with the development not only of bite, which we discussed in the fourth chapter, but also of more acute hearing. Moreover, what helped mammals improve their hearing was not the appearance of new bones, but the adaptation of old ones to perform new functions. Bones that originally served to help reptiles bite now help mammals hear.

This, it turns out, is where the hammer and the anvil came from. But where, in turn, did the stirrup come from?

If I just showed you how an adult and a shark work, you would never guess that this tiny bone in the depths of the human ear corresponds to the large cartilage in the upper jaw of a marine predator. However, by studying the development of humans and sharks, we are convinced that this is exactly the case. The stapes is a modified skeletal structure of the second branchial arch similar to that of a shark's cartilage, which is called the pendulum, or hyomandibular. But the pendant is not the bone of the middle ear, because sharks do not have ears. In our aquatic relatives - cartilaginous and bony fish - this structure connects the upper jaw with the skull. Despite the obvious difference in the structure and functions of the stapes and pendulum, their relationship is manifested not only in their similar origin, but also in the fact that they are served by the same nerves. The main nerve leading to both these structures is the nerve of the second arch, that is, the facial nerve. So, we have before us a case where two completely different skeletal structures have a similar origin during embryonic development and a similar innervation system. How can this be explained?

Once again, we should turn to fossils. If we trace the changes in the pendant from cartilaginous fishes to such creatures as Tiktaalik, and further to amphibians, we are convinced that it gradually decreases and finally separates from the upper jaw and becomes part of the organ of hearing. At the same time, the name of this structure also changes: when it is large and supports the jaw, it is called the dewlap, and when it is small and participates in the work of the ear, it is called the stapes. The transition from pendant to stirrup occurred when the fish came to land. To hear in water, you need completely different organs than on land. The small size and position of the stirrup perfectly allow it to capture small vibrations occurring in the air. And this structure arose due to modifications in the structure of the upper jaw.

We can trace the origin of our auditory ossicles from the skeletal structures of the first and second branchial arches. The history of the malleus and incus (left) is shown from ancient reptiles, and the history of the stapes (right) is shown from even more ancient cartilaginous fish.

Our middle ear stores traces of two major changes in the history of life on Earth. The appearance of the stapes - its development from the suspension of the upper jaw - was caused by the transition of fish to life on land. In turn, the malleus and incus arose during the transformation of ancient reptiles, in which these structures were part of the lower jaw, into mammals, for whom they help to hear.

Let's look deeper into the ear - into the inner ear.

Inner ear - movement of jelly and vibration of hairs

Imagine that we enter the ear canal, pass through the eardrum, past the three bones of the middle ear and find ourselves deep inside the skull. This is where the inner ear is located - tubes and cavities filled with a jelly-like substance. In humans, as in other mammals, this structure resembles a snail with a curled shell. Her characteristic appearance immediately catches the eye when we dissect bodies in anatomy classes.

Different parts of the inner ear perform different functions. One of them is for hearing, the other is to tell us how our head is tilted, and the third is for us to feel how the movement of our head is speeding up or slowing down. All of these functions are carried out in the inner ear in a fairly similar way.

All parts of the inner ear are filled with a jelly-like substance that can change its position. Special nerve cells send their endings to this substance. When this substance moves, flowing inside the cavities, the hairs at the ends of the nerve cells bend as if by the wind. When they bend, nerve cells send electrical impulses to the brain, and the brain receives information about sounds and the position and acceleration of the head.

Every time we tilt our heads, tiny pebbles move out of place in the inner ear, lying on the shell of the cavity filled with a jelly-like substance. The flowing substance affects the nerve endings inside this cavity, and the nerves send impulses to the brain telling it that the head is tilted.

To understand the principle of operation of the structure that allows us to feel the position of the head in space, imagine a Christmas toy - a hemisphere filled with liquid in which “snowflakes” float. This hemisphere is made of plastic, and it is filled with a viscous liquid, in which, if you shake it, a blizzard of plastic snowflakes begins. Now imagine the same hemisphere, only made not of a solid, but of an elastic substance. If you sharply tilt it, the liquid in it will move, and then the “snowflakes” will settle, but not to the bottom, but to the side. This is exactly what happens in our inner ear, only in a greatly reduced form, when we tilt our head. In the inner ear there is a cavity with a jelly-like substance into which nerve endings emerge. The flow of this substance allows us to feel what position our head is in: when the head tilts, the substance flows to the appropriate side, and impulses are sent to the brain.

Additional sensitivity is given to this system by tiny pebbles lying on the elastic shell of the cavity. When we tilt our heads, the pebbles rolling in the liquid medium press on the shell and increase the movement of the jelly-like substance enclosed in this shell. Due to this, the entire system becomes even more sensitive and allows us to perceive even small changes in the position of the head. As soon as we tilt our heads, tiny pebbles are already rolling around inside our skull.

You can imagine how difficult it is to live in space. Our senses are configured to work under the constant influence of Earth's gravity, and not in low-Earth orbit, where the Earth's gravity is compensated by the movement of the spacecraft and is not felt at all. An unprepared person in such conditions becomes ill, because the eyes do not allow one to understand where is up and where is down, and the sensitive structures of the inner ear are completely confused. This is why space sickness is a serious problem for those who work on orbital vehicles.

We perceive acceleration due to another structure of the inner ear, connected to the other two. It consists of three semicircular tubes, also filled with a jelly-like substance. Whenever we accelerate or brake, the substance inside these tubes shifts, tilting the nerve endings and causing impulses to travel to the brain.

Whenever we speed up or slow down, it causes the jelly-like substance in the semicircular tubes of the inner ear to flow. The movements of this substance cause nerve impulses sent to the brain.

Our entire system for perceiving the position and acceleration of the body is connected with the eye muscles. Eye movement is controlled by six small muscles attached to the walls of the eyeball. Their contraction allows you to move your eyes up, down, left and right. We can voluntarily move our eyes, contracting these muscles in a certain way when we want to look in some direction, but their most unusual property is the ability to work involuntarily. They control our eyes all the time, even when we don't think about it at all.

To assess the sensitivity of the connection between these muscles and the eyes, move your head this way and that way without taking your eyes off this page. Moving your head, look intently at the same point.

What happens? The head moves, but the position of the eyes remains almost unchanged. Such movements are so familiar to us that we perceive them as something simple, self-evident, but in reality they are extremely complex. Each of the six muscles that control each eye responds sensitively to any movement of the head. Sensitive structures located inside the head, which will be discussed below, continuously record the direction and speed of its movements. From these structures signals go to the brain, which in response to them sends other signals that cause contractions of the eye muscles. Remember this the next time you stare at something while moving your head. This complex system can sometimes malfunction, which can tell a lot about what problems in the body’s functioning are caused.

To understand the connections between the eyes and the inner ear, the easiest way is to cause various disruptions to these connections and see what effect they produce. One of the most common ways to cause such disorders is through excessive alcohol consumption. When we drink a lot of ethyl alcohol, we say and do stupid things because alcohol weakens our internal limiters. And if we drink not just a lot, but a lot, we also start to feel dizzy. Such dizziness often foreshadows a difficult morning - we are in for a hangover, the symptoms of which will be new dizziness, nausea and headache.

When we drink too much, we have a lot of ethyl alcohol in our blood, but the alcohol does not immediately enter the substance that fills the cavities and tubes of the inner ear. Only some time later it leaks from the bloodstream into various organs and ends up in the jelly-like substance of the inner ear. Alcohol is lighter than this substance, so the result is about the same as pouring a little alcohol into a glass of olive oil. This creates random swirls in the oil, and the same thing happens in our inner ear. These chaotic turbulences cause chaos in the body of an intemperate person. The hairs at the ends of the sensory cells vibrate, and the brain thinks that the body is in motion. But it doesn't move - it rests on the floor or on the bar counter. The brain is deceived.

Vision is also not left out. The brain thinks that the body is rotating, and it sends corresponding signals to the eye muscles. The eyes begin to move to one side (usually to the right) when we try to keep them focused on something by moving our head. If you open the eye of a dead drunk person, you can see characteristic twitching, the so-called nystagmus. This symptom is well known to police officers, who often test drivers stopped for careless driving for it.

With a severe hangover, something different happens. The next day after drinking, the liver had already removed alcohol from the blood. She does this surprisingly quickly and even too quickly, because alcohol still remains in the cavities and tubes of the inner ear. It gradually leaks from the inner ear back into the bloodstream and in the process again agitates the jelly-like substance. If you take the same dead-drunk person whose eyes twitched involuntarily in the evening, and examine him during a hangover, the next morning, you may find that his eyes twitch again, only in a different direction.

We owe all this to our distant ancestors - fish. If you've ever fished for trout, you've probably encountered the workings of the organ from which our inner ear apparently originates. Fishermen are well aware that trout stay only in certain areas of the riverbed - usually where they can be especially successful in obtaining food for themselves while avoiding predators. These are often shaded areas where the current creates eddies. Large fish are especially willing to hide behind large stones or fallen trunks. Trout, like all fish, has a mechanism that allows it to sense the speed and direction of movement of the surrounding water, much like the mechanism of our senses of touch.

In the skin and bones of fish there are small sensitive structures that run in rows along the body from head to tail - the so-called lateral line organ. These structures form small tufts from which miniature hair-like projections emerge. The outgrowths of each bundle protrude into a cavity filled with a jelly-like substance. Let's remember once again the Christmas toy - a hemisphere filled with a viscous liquid. The cavities of the lateral line organ also resemble such a toy, only equipped with sensitive hairs looking inward. When water flows around the body of a fish, it presses on the walls of these cavities, forcing the substance filling them to move and tilting the hair-like outgrowths of nerve cells. These cells, like the sensory cells in our inner ear, send impulses to the brain that enable the fish to sense the movement of the water around it. Both sharks and bony fish can sense the direction of water movement, and some sharks even sense small turbulence in the surrounding water, caused, for example, by other fish swimming by. We used a system very similar to this one, where we looked intently at one point, moving our heads, and saw disruptions in its operation when we opened our eyes to a drunk person. If our ancestors, common to sharks and trout, had used some other jelly-like substance in the lateral line organs, in which turbulence would not have arisen when alcohol was added, we would never have become dizzy from drinking alcoholic beverages.

It is likely that our inner ear and the fish's lateral line organ are variants of the same structure. Both of these organs are formed during development from the same embryonic tissue and are very similar in internal structure. But which came first, the lateral line or the inner ear? We do not have clear data on this matter. If we look at some of the oldest head-bearing fossils, which lived about 500 million years ago, we see small pits in their dense protective coverings, which leads us to assume that they already had a lateral line organ. Unfortunately, we know nothing about the inner ear of these fossils because we have no specimens that preserve this part of the head. Until we have new data, we are left with an alternative: either the inner ear developed from the lateral line organ, or, conversely, the lateral line developed from the inner ear. In any case, this is an example of a principle that we have already observed in other structures of the body: organs often arise to perform one function, and then are rebuilt to perform a completely different one - or many others.

Our inner ear has grown larger than that of fish. Like all mammals, the part of the inner ear responsible for hearing is very large and curled, like a snail. In more primitive organisms, such as amphibians and reptiles, the inner ear is simpler and not curled like a snail. Obviously, our ancestors - ancient mammals - developed a new, more effective hearing organ than their reptilian ancestors had. The same applies to structures that allow you to feel acceleration. In our inner ear there are three tubes (semicircular canals) responsible for sensing acceleration. They are located in three planes, lying at right angles to each other, and this allows us to feel how we move in three-dimensional space. The oldest known vertebrate to possess such canals, the hagfish-like jawless one, had only one canal in each ear. Later organisms already had two such channels. And finally, most modern fish, like other vertebrates, have three semicircular canals, like us.

As we have seen, our inner ear has a long history, dating back to the earliest vertebrates, even before the appearance of fish. It is noteworthy that the neurons (nerve cells) whose endings are embedded in a jelly-like substance in our inner ear are even older than the inner ear itself.

These cells, the so-called hair-like cells, have characteristics not found in other neurons. The hair-like outgrowths of each of these cells, including one long “hair” and several short ones, and these cells themselves, both in our inner ear and in the lateral line fish organ, are strictly oriented. Recently, a search has been made for such cells in other animals, and they were found not only in organisms that do not have such developed sensory organs as we do, but also in organisms that do not even have a head. These cells are found in lancelets, which we met in the fifth chapter. They have no ears, no eyes, no skull.

Therefore, hair cells appeared long before our ears arose, and initially performed other functions.

Of course, all this is written in our genes. If a mutation occurs in a person or mouse that turns off a gene Pax 2, a full inner ear does not develop.

A primitive version of one of the structures of our inner ear can be found under the skin of fish. Small cavities of the lateral line organ are located along the entire body, from head to tail. Changes in the flow of surrounding water deform these cavities, and the sensory cells located in them send information about these changes to the brain.

Gene Pax 2 works in the embryo in the area where ears are formed, and likely sets off a chain reaction of genes turning on and off that leads to the formation of our inner ear. If we look for this gene in more primitive animals, we will find that it works in the head of the embryo, and also, imagine, in the rudiments of the lateral line organ. The same genes are responsible for dizziness in drunk people and the feeling of water in fish, suggesting that these different feelings have a common history.

Jellyfish and the origin of eyes and ears

Similar to the gene responsible for eye development Pax 6, which we have already discussed, Pax 2, in turn, is one of the main genes necessary for ear development. Interestingly, these two genes are quite similar. This suggests that eyes and ears may come from the same ancient structures.

Here we need to talk about box jellyfish. Those who regularly swim in the sea off the coast of Australia are well aware of them, because these jellyfish have an unusually strong poison. They differ from most jellyfish in that they have eyes - more than twenty of them. Most of these eyes are simple pits scattered in the integument. But several eyes are surprisingly similar to ours: they have something like a cornea and even a lens, as well as an innervation system similar to ours.

Jellyfish have neither Pax 6, nor Pax 2 - these genes arose later than jellyfish. But we find something quite remarkable among box jellyfish. The gene that is responsible for the formation of their eyes is not a gene Pax 6, nor the genome Pax 2, but is like a mosaic mixture both of these genes. In other words, this gene looks like a primitive version of the genes Pax 6 And Pax 2 characteristic of other animals.

The most important genes that control the development of our eyes and ears, in more primitive organisms - jellyfish - correspond to a single gene. You may ask: “So what?” But this is a pretty important conclusion. The ancient connection we discovered between ear and eye genes helps us understand much of what modern doctors face in their practice: many of the human birth defects affect on both of these organs- both before our eyes and ears. And it all reflects our deep connection with creatures like the poisonous sea jellyfish.

It is not surprising that the hearing aid is considered to be the most perfect sensory organ in humans. It contains the highest concentration of nerve cells (over 30,000 sensors).

Human hearing aid

The structure of this apparatus is very complex. People understand the mechanism by which sounds are perceived, but scientists do not yet fully understand the sensation of hearing, the essence of signal transformation.

The structure of the ear consists of the following main parts:

• external;
• average;
• internal.

Each of the above areas is responsible for performing a specific job. The outer part is considered a receiver, which perceives sounds from the external environment, the middle part is an amplifier, and the inner part is a transmitter.

Structure of the human ear

The main components of this part:

• ear canal;
• auricle.

The auricle consists of cartilage (it is characterized by elasticity and elasticity). The skin covers it on top. At the bottom there is a lobe. This area has no cartilage. It includes adipose tissue and skin. The auricle is considered a rather sensitive organ.

Anatomy

The smaller elements of the auricle are:

• curl;
• tragus;
• antihelix;
• helix legs;
• antitragus.

Kosha is a specific covering lining the ear canal. It contains glands that are considered vital. They secrete a secret that protects against many agents (mechanical, thermal, infectious).

The end of the passage is represented by a kind of dead end. This specific barrier (tympanic membrane) is necessary to separate the outer and middle ear. It begins to vibrate when sound waves hit it. After the sound wave hits the wall, the signal is transmitted further, towards the middle part of the ear.

Blood flows to this area through two branches of arteries. The outflow of blood is carried out through the veins (v. auricularis posterior, v. retromandibularis). localized in front, behind the auricle. They also carry out the removal of lymph.

The photo shows the structure of the outer ear

Functions

Let us indicate the significant functions that are assigned to the outer part of the ear. She is capable of:

• receive sounds;
• transmit sounds to the middle part of the ear;
• direct the sound wave to the inside of the ear.

Possible pathologies, diseases, injuries

Let us note the most common diseases:

Average

The middle ear plays a huge role in signal amplification. Strengthening is possible thanks to the auditory ossicles.

Structure

Let us indicate the main components of the middle ear:

• tympanic cavity;
• auditory (Eustachian) tube.

The first component (the eardrum) contains a chain inside, which includes small bones. The smallest bones play an important role in transmitting sound vibrations. The eardrum consists of 6 walls. Its cavity contains 3 auditory ossicles:

• hammer. This bone has a rounded head. This is how it is connected to the handle;
• anvil. It includes a body, processes (2 pieces) of different lengths. Its connection with the stirrup is made through a slight oval thickening, which is located at the end of the long process;
• stirrup. Its structure includes a small head bearing the articular surface, an anvil, and legs (2 pcs.).

The arteries go to the tympanic cavity from a. carotis externa, being its branches. Lymphatic vessels are directed to the nodes located on the side wall of the pharynx, as well as to those nodes that are localized behind the concha.

Structure of the middle ear

Functions

Bones from the chain are needed for:

1. Carrying out sound.
2. Transmission of vibrations.

The muscles located in the middle ear area specialize in performing various functions:

• protective. Muscle fibers protect the inner ear from sound stimulation;
• tonic. Muscle fibers are necessary to maintain the chain of auditory ossicles and the tone of the eardrum;
• accommodative The sound-conducting apparatus adapts to sounds endowed with different characteristics (strength, height).

Pathologies and diseases, injuries

Among the popular diseases of the middle ear we note:

• (perforative, non-perforative,);
• catarrh of the middle ear.

Acute inflammation can occur with injuries:

• otitis, mastoiditis;
• otitis, mastoiditis;
• , mastoiditis, manifested by wounds of the temporal bone.

It can be complicated or uncomplicated. Among the specific inflammations we indicate:

• syphilis;
• tuberculosis;
• exotic diseases.

Anatomy of the outer, middle, inner ear in our video:

Let us point out the significant importance of the vestibular analyzer. It is necessary to regulate the position of the body in space, as well as to regulate our movements.

Anatomy

The periphery of the vestibular analyzer is considered a part of the inner ear. In its composition we highlight:

• semicircular canals (these parts are located in 3 planes);
• statocyst organs (they are represented by sacs: oval, round).

The planes are called: horizontal, frontal, sagittal. The two sacs represent the vestibule. The round pouch is located near the curl. The oval sac is located closer to the semicircular canals.

Functions

Initially, the analyzer is excited. Then, thanks to the vestibulospinal nerve connections, somatic reactions occur. Such reactions are needed to redistribute muscle tone and maintain body balance in space.

The connection between the vestibular nuclei and the cerebellum determines mobile reactions, as well as all reactions to coordinate movements that appear when performing sports and labor exercises. To maintain balance, vision and muscle-articular innervation are very important.