Tympanic membrane retraction caused by erosion of the ossicles (hearing bones). Discharge from the ear often indicates that the retraction pocket has developed into a cholesteatoma. Three factors must occur for the tympanic membrane to become retracted: When gas pressure within the middle ear is less than atmospheric pressure, the eardrum can become sucked into the middle ear space. This is caused by inadequate opening of the Eustachian tube and absorption of air from the middle ear space. People with a patulous Eustachian tube may also cause negative middle ear pressure by repeatedly sniffing to try to keep their Eustachian tube closed. The
Common name of the general public (including such interested parties as fishermen, farmers, etc.) to be able to refer to one particular species of organism without needing to be able to memorise or pronounce the Latinized scientific name. Creating an "official" list of common names can also be an attempt to standardize the use of common names, which can sometimes vary a great deal between one part of a country and another, as well as between one country and another country, even where the same language is spoken in both places. A common name intrinsically plays a part in a classification of