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Ear hammer anvil and stirrup8/13/2023 ![]() ![]() ![]() Directly behind and connected to the eardrum-which is essentially, a large collector of sound-is the hammer. The hammer is arranged so that one end is attached to the eardrum, while the other end forms a lever-like hinge with the anvil. ![]() The opposite end of the anvil is fused with the stirrup (so anvil and stirrup act as one bone). The stirrup then connects with a special opening in the cochlea called the "oval window." The footplate of the stirrup-the oval, flat part of the bone that resembles the part where one would rest ones foot in an actual stirrup-is loosely attached to the oval window of the cochlea, allowing it to move in and out like a piston. The piston-like action generates vibrations in the fluid-filled inner ear that are used to signal the brain of a sound event. Without the middle ear ossicles, only about 0.1 percent of sound energy would make it into the inner ear. Overcoming the problem of getting airborne sound into the fluid-filled inner ear is solved by two main mechanisms: the concentration of energy from the large eardrum onto the small stirrup footplate situated in the oval window and the lever-like action between the hammer and the anvil-stirrup complex. On our website, you can learn about all parts of the human ear, understand the functions and parts of the outer ear and the inner ear.In cats, for example, the simple concentration of forces from the eardrum to the stirrup increases pressure at the oval window to about 35 times what is measured at the eardrum. The middle ear is only one part of the fascinating apparatus that enables us not only to hear, but also to maintain our balance. Built-up pressure in the ear will often occur in situations where the pressure keeps changing, for example when flying or driving in mountainous areas. A large difference in pressure will cause discomfort and even slight pain. The limited vibration results in a slight reduction in hearing ability. If the pressure is not equalised, a pressure will build up on the eardrum, preventing it from vibrating properly. The swallowing action will force the tube connecting the palate with the ear to open, thus equalising the pressure.īuilt-up pressure in the ear may occur in situations where the pressure on the inside of the eardrum is different from that on the outside of the eardrum. In most cases the pressure is equalised automatically, but if this does not occur, it can be brought about by making an energetic swallowing action. The tube opens when you swallow, thus equalising the air pressure inside and outside the ear. The Eustachian tube’s function is to equalise the air pressure on both sides of the eardrum, ensuring that pressure does not build up in the ear. It connects the ear with the rearmost part of the palate. What is the Eustachian tube? Another important middle ear function is carried out by the Eustachian tube, which is also found in the middle ear. In doing so, it allows fluid in the cochlea to move. In the middle ear, the round window vibrates in opposite phase to vibrations entering the inner ear through the oval window. The same principle applies when a person wearing a shoe with a sharp stiletto heel steps on your foot: The small surface of the heel causes much more pain than a flat shoe with a larger surface would. The pressure is increased due to the difference in size between the relatively large surface of the eardrum and the smaller surface of the oval window. ![]() The pressure of the sound waves on the oval window is some 20 times higher than on the eardrum. When the sound waves are transmitted from the eardrum to the oval window, the middle ear is functioning as an acoustic transformer amplifying the sound waves before they move on into the inner ear. When the eardrum vibrates, the sound waves are transferred to the middle ear bones and travel via the hammer and anvil to the stirrup and then on to the oval window. What is the oval window? In the middle ear, the oval window is a membrane covering the entrance to the cochlea in the inner ear. These three middle ear bones form a kind of bridge, and the stirrup, which is the last bone that sounds reach, is connected to the oval window. The vibrations are transmitted further into the ear via three bones in the middle ear: the hammer (malleus), the anvil (incus) and the stirrup (stapes). Unilateral hearing loss - Single sided deafness. ![]()
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