ASSIGNMENT 6: REDUCED MIDDLE EAR DRAINAGE

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NOTE: CLICK ON THE IMAGES FOR A LARGER VIEW

THE MIDDLE EAR CAVITY

The middle ear cavity helps converts sound waves into electrical signals. It is a sort of a middle man between the mechanical sound waves that travel via the external ear and the electrical impulses generated by the internal ear. Consider the middle ear to be the equalent of the part of the microphone that reverbates in response to sound waves

THE MIDDLE EAR STRUCTURE

The following is a simplistic layout of the middle ear cavity

The bones are shown in yellow, the ear drum (tympanic membrane is in grey. They cavity itself is shown in a blue tint.

THE MIDDLE EAR WORKINGS

The sound waves travel via the external auditory meatus to the ear drum. They ear drum starts to vibrate as the sound waves strike it. The vibrating ear drum then moves the bony complex (Malleus + Incus + Stapes). The sound energy is thus converted to mechanical energy (characterized by the movement of the bones). The foot plate of stapes helps to transmit this mechanical energy to internal ear (via the oval window) where it is converted into electrical signals. More information is available here

THE MIDDLE EAR LUBRICATION

Most of the middle ear is composed of parts that constantly move in response to sound waves. They need some form of "lubrication" to keep things working. This is done by the mucus which is produced by the epithelial lining of the middle ear cavity. Eventually the mucus is driven out of the middle ear via the eustachian tube.

THE MIDDLE EAR LUBRICATION: GONE WRONG

If mucus starts accumulating in the middle ear cavity (either due to its over production or under drainage as a result of blockage of the eustachian tube), the middle will start filling up with mucus. Think of a ship's engine room which is starting to flood and the pumps to drive the water out aren't working. A time will come when the entire engine room will be flooded and the engine would die off. Similarly the excess mucus will lead to the middle ear machinery getting "gunked" and it will stop working. This will result in deafness.

This is a relatively slow process and takes some time to develop. Once fully developed it is called Chronic (it is a slow process) Serous (as opposed to purulent caused by infection) Otitis (oto= ear) Media, CSOM for short.

It has recently been shown that children with nasal allergies (allergic rhinitis) are predisposed to developing this condition. Your task is to look for evidence that might support this theory.