Organ of Corti: characteristics of this part of the inner ear

Our ability to perceive what is going on around us is a key element in allowing us to survive. Of all the senses, the most developed in humans is that of sight. But probably after that, the next thing that strikes us as the most relevant when it comes to scanning the environment is the ear.

Thanks to our hearing, we are able to perceive the vibrations which generate elements as relevant as the movements of stimuli or our distance from them. And it even allows us to generate and capture speech, or enjoy music. But for that, we need something that turns the vibrations into something treatable. And in the auditory system there is a fundamental organ in this process: Corti’s organ.

    The organ of Corti: an important part of the hearing system

    It is called the organ of Corti a small structure present in our hearing system which is of utmost importance for this system, as it is responsible for taking the first step in transforming environmental vibrations into stimuli that can be interpreted by our nervous system and without it we could not hear.

    This spiral-shaped organ is part of the inner ear and is part of the auditory neuroepithelium. It is located in the cochlea, More precisely on the median ramp of this one, supported on the basilar membrane.

    The organ Corti is a sensory structure in which along four large rows there are different types of cells, mainly hairy, which have mechanoreceptors and which connect to the auditory nerve (the bodies of neurons of cranial pair VIII are found in organ of Corti).

    These cells, which are found in large numbers (between 16,000 and 24,000), are the main receiver of sounds that reach us.

    The relevant role of this body: how do we feel?

    Perhaps one of the most important parts of the auditory system is the organ of Corti, and it is thanks to it that our bodies are able to transduce external stimuli.

    To better understand how it works, we must keep in mind that the sounds we perceive are waves of different frequencies, which generate a vibration when emitted. But our nervous system does not function with these waves without more: there must be an organ or an element which receives this information, of mechanical type, and transforms it into a bioelectric pulse can travel and be interpreted by the brain. And in this case, that receptor is the organ of Corti, or rather the hair cells that are part of it.

    When we hear something, we actually pick up vibrations, which reach our auditory system through the ear pinna and travel through the different parts of the outer and middle ear: the ear canal, eardrum, and bear chain ( including hammer and stirrup), as well as the Eustachian tube, up to the oval window, a membrane that covers the cochlea and from which the inner ear begins.

    In the cochlea there are different parts, one of them being the basilar membrane. The vibrations which arrive will generate a wave which will cause a movement of the cells which rest on it, Who are those that are part of the organ Corti, so that this movement causes the opening of ion channels which will eventually generate depolarization, transforming the mechanical wave into a bioelectric signal.

    In addition to the simple perception of sound, according to the tonotopic theory thanks to the organ Corti, we can also differentiate different tones and volumes, depending on the area in which the movement of the basilar membrane generates the maximum stimulation of the cells. cells. Furthermore, from the observation of cases in which there is damage in this area and in the cochlea, it has been observed that there is a relationship between the organ of Corti and balance.

    Major types of hair cells

    As we mentioned, the organ Corti is made up of a series of cells that allow us to transform vibrations into sounds. The main cells responsible for this phenomenon are the hair cells. However, not all cells in the organ Corti are the same, but we can find two types.

    Internal hair cells

    The inner hair cells (we have about 3500 of them) are in fact the sound receptors of the auditory system, that is to say those elements which generate the transduction of information from the vibration to the electrical impulse.

    These are cells which rely on the basilar membrane and which they are connected to the auditory nerve, And the action occurs when the movement of it causes the displacement of the liquid in which they are immersed or endolymph.

    This generates a movement of the eyelashes, that open channels through which sodium and potassium ions enter in such a way that they end up causing a depolarization, in which the glutamate will be released in the neurons which innervate them and generate that they generate the electrical impulse and transport it to the central nervous system.

    Outer hair cells

    The outer hair cells (around 12,000) differ from the previous ones in that they are actually attached to the tentoria membrane by their longer cilia, while in contact with the basilar from other supporting cells, Deiters cells. The outer hairs are completely affected by the movement of the basilar membrane, regardless of the movement of the endolymph.

    Their function is not to generate electrical stimuli from mechanics so that the brain can process them, but rather to do the opposite in order to be able to modulate the selectivity of the frequencies that we receive. They are mainly modulators.

    Support cells

    Although hair cells are the most relevant cells to explain how the organ Corti works, it should be mentioned that in addition to them within this organ, we can find cells that support them and allow their survival. . These are, for example, the aforementioned Deiters and Hansen cells (which are attached to them).

    Problems related to injuries of this organ

    Organ of Corti and cochlea these are fundamental elements in the perception of sound, So the existence of diseases or injuries that impair their functioning or destroy them will have serious consequences in this regard. The causes that can generate this type of injury can be found in trauma, tumors, infections, aging of the hearing system or problems with irrigation.

    Degeneration or damage to the organ of Corti can cause alterations such as the presence of tinnitus, echoes, hearing loss or sensorineural hearing loss, pain relievers (Hearing pain) or even diploacusias (double perception of the same sound, even in the same direction).

    The complete loss of the said organ would lead to deafness, As we would not be able to process the auditory information. Also alterations in balance.

    Bibliographical references:

    • Tresguerres, JAF, Ariznavarreta, C., Cachofeiro, V., Cardinali, D., Escrich, E., Gil, P., Lahera, V., Mora, F., Romano, M., Tamargo, J. (2005 ). Human physiology. 3rd Edition. McGraw Hill.

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