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The Fantastic Journey of the Ear: How do the outer ear, middle ear, and inner ear work together?
The ear is not only an important organ for us to listen to music and talk, but also a core part of the auditory system. Its complex structure enables us to perceive sounds from the outside through the collaborative work of the outer ear, middle ear, and inner ear. In this article, we’ll take a closer look at how these three parts work together and their important role in the hearing process.
The role of the outer ear
The outer ear includes the visible pinna and ear canal, and is finally bounded by the tympanic membrane. The main function of the auricle is to focus sound waves and guide them into the ear canal. The structural design of the ear canal also facilitates the transmission of sound. When the sound wave reaches the eardrum, it vibrates according to the waveform of the sound wave.
The external structure of the ear allows animals to locate sounds based on their source, improving their chances of survival in nature.
The tympanic membrane is a closed membrane that vibrates under the influence of sound waves, and the vibrated signals are transmitted to the middle ear. Earwax (earwax) in the outer ear is produced by the skin glands in the ear canal. Its main function is to protect the ear canal and eardrum from physical damage and bacterial invasion.
The key role of the middle ear
The middle ear is an air-filled chamber located inside the eardrum. Its interior contains the three smallest bones, collectively called the ossicles, the malleus, stapes, and incus. Their function is to transmit vibrations from the eardrum to the cochlea in the inner ear.
The design of the ossicles in the middle ear enables it to overcome the impedance difference between air waves and cochlear waves, thereby ensuring effective sound transmission.
There are also two muscles in the middle ear. The function of the muscles is to protect the hearing mechanism. When excessive sound occurs, these muscles will perform a contraction reflex. When sound waves enter the round window, they are passed to the inner ear.
The mystery of the inner ear
The main component of the inner ear is the cochlea, a spiral, fluid-filled tube. The organ of Coti within the cochlea is the primary mechanical to neural transducer. As waves from the middle ear pass through the cochlear fluid, the basilar membrane vibrates and begins to convert signals.
Vibrations of the basilar membrane cause depolarization of specialized auditory cells (hair cells), which interact with the fibers of the auditory nerve to generate nerve impulses that transmit sound information to the brain.
Sound information from the cochlea is transmitted through the auditory nerve to the cochlear nucleus in the brainstem, then integrated to the hypothalamus at the base of the midbrain, and finally transmitted from the thalamus to the primary auditory cortex in the temporal lobe. Here, for the first time, we become aware of the existence of sound.
Hearing testing and hearing loss
Hearing can be measured with behavioral and electrophysiological tests that accurately determine hearing thresholds. Different types of hearing loss (such as conductive, sensorineural, and mixed) can affect auditory function. In recent years, a new term "Aural Diversity" has emerged to provide a less negative description of hearing loss and differences.
Although hearing loss can be divided into many types, the causes behind it include genetics, noise damage, infection, and more.
Further research has shown a clear link between hearing loss and Alzheimer's disease and type 2 diabetes.
Prevention and management of hearing loss
To prevent noise-induced hearing loss, common measures include using earplugs or earmuffs and adjusting the noise level in the environment. When hearing loss occurs, although there is currently no cure for neurological loss, hearing aid devices such as earphones and cochlear implants can effectively improve the quality of life.
The mysterious world of ears
From the physical process of hearing to the nerve transmission in the brain, every structure of the ear is delicate and coordinated. All this enables us to feel the sounds from the world and enhances human beings' ability to survive and communicate. However, do we really pay attention to all this and always look back to care about our hearing health?
