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( Middle ear)
The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has also been called the tympanic cavity, or cavum tympani. The eustachian tube joins the tympanic cavity with the nasal cavity (nasopharynx), allowing pressure to equalize between the inner ear and throat. The primary function of the middle ear is to efficiently transfer acoustic energy from compression waves in air to fluid–membrane waves within the cochlea. Ordinarily, when sound waves in air strike liquid, most of the energy is reflected off the surface of the liquid. The middle ear allows the impedance matching of sound traveling in air to acoustic waves traveling in a system of fluids and membranes in the inner ear. This system should not be confused, however, with the propagation of sound as compression waves in a liquid. The middle ear couples sound from air to the fluid via the oval window, using the principle of "mechanical advantage" in the form of the "hydraulic principle" and the "lever principle".[1] The vibratory portion of the tympanic membrane is many times the surface area of the footplate of the stapes; furthermore, the shape of the articulated ossicular chain is like a lever, the long arm being the long process of the malleus, and the body of the incus being the fulcrum and the short arm being the lenticular process of the incus. The collected pressure of sound vibration that strikes the tympanic membrane is therefore concentrated down to this much smaller area of the footplate, increasing the force but reducing the velocity and displacement, and thereby coupling the acoustic energy.
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Middle ear Subcategories
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Middle ear Articles
Fit over 40 by Doug Setter
Staying Fit Over Forty By: Doug Setter Article ID: 1424011 Article Submitted: August 19, 2008 Category: Health and Fitness :: Exercise Article Word Count: 678 Now in my 50's, I learned the hard way that you cannot train the same a...
Diagnosing Middle Back Pain by Terry O'Brien
The facts are that the vast majority of back pains normally occur in the lower back, mid back and the upper back. Of these, mid back pain is quite rare. The middle portion of the body is built for strength and stability, so that the vital internal...
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