Other conditions develop over time, the most common of which is ossicular chain discontinuity, which means two or all of the bones are fused together or situated too far apart. Roughly 1 person in 10,000 is born with a malformation of the auditory ossicles on one or both sides, limiting their ability to hear. Unfortunately, there are a number of things that can go wrong with this delicate network of bones, including natural anatomical variations. Possible Conditions of the Auditory Ossicles These signals then embark on a short voyage to the brain via the vestibulocochlear nerve. When the oval window starts to move, it causes turbulence in the cochlear fluid, and the tiny ripples formed stimulate the receptor cells, thereby transferring the mechanical data that started at the ear canal, into electric signals. Just beyond the oval window is the cochlear, a snail shell-shaped cavity filled with fluid and thousands of infinitesimal receptor cells. This means the vibrations reach peak strength at the stapes, just before hitting the oval window.
The smaller the bone, the more furiously the vibrations can shake it, amplifying the signal. There’s a reason the auditory ossicles get smaller in sequence. The incus then passes the sonic news on to the stapes, completing the chain of vibration. The vibrations travel along the neck and head of the malleus, over to the incus via the incudomalleolar joint. These vibrations are picked up by the spatulate process and handle of the malleus, which, in turn, starts to vibrate. Sound waves wriggle their way into our ear canals, which herds them like sheep towards our eardrums, which vibrate in response. Simply put, the auditory ossicles facilitate the transformation of sound waves to electrical signals that the brain can read. What Is the Purpose of the Auditory Ossicles? We can’t feel it, but these joints allow the auditory ossicles to shift or dance in response to signals picked up by our eardrums, although their movement is quite limited. These specialist connections are known as incudomalleolar joints, and the joint that connects the stapes to the oval window is called a tympanostapedial joint. Much like all the other larger bones in our bodies, the auditory ossicles are interconnected by joints, but these aren’t your garden variety ball and socket or hinge joints. The limbs of the stapes curve out from the head, traveling in tandem to the base, giving the bone its stirrup-like appearance. Stapesĭespite being the smallest of all three ossicles, the stapes has four distinct sections: the head (capitum), the base (footplate), and the two limbs (anterior and posterior). The long limb of the incus travels towards the inside of the head (a diversion known as the lenticular process) before meeting the stapes. Attached to the rear wall of the eardrum by a ligament, the short limb provides the stability required of this central bone. The incus only consists of two parts, or limbs: the short limb and the long limb. It’s both the fulcrum that facilitates the rotation of the malleus and incus connection, as well as a damper for loud low frequencies.Ī larger cone-shaped extension, the lateral process, is situated between the base of the handle and the eardrum, held fast by three ligaments. The anterior extension terminates in a tiny gap in the skull. It’s composed of five distinct sections: the head, the neck, the handle, and two extensions known as the anterior and lateral processes. The malleus, or hammer, is the largest of the auditory ossicles. Structure of the Auditory Ossicles Malleus The incus travels along the middle ear, eventually meeting up with the last of the trio, the stapes, which runs through to the fenestra ovalis (oval window) at the threshold of the inner ear. The first in sequence is the malleus, which runs from the edge of the tympanic membrane, or in other words, the eardrum, through to the second bone in sequence, the incus. This tiny team of bones forms a chain connecting the inner and middle ear. Individually, they’re known as the malleus, incus, and stapes however, as they all have rather striking appearances, they’re commonly referred to as their shapes: hammer, anvil, and stirrup.
There are 6 of them in total, 3 in each ear.
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The reason they’re quite renowned is that they’re the smallest bones in the entire human body.
#AUDITORY TUBE TV#
You may have heard of the auditory ossicles before - perhaps they were an answer to a quiz on TV or at a bar. What and Where Are the Auditory Ossicles?
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