. On the other hand, contraction of the stapedius raws the stapes more outwards

contraction, protecl the organ ofCorti as well as the ear drum from damage. Loud sounds of ery abrupt origin, then, are particularly damaging Fig. 10B2.4.2b. The contents of the internal ear Other probable motions of MEMs ace. that they probably contribute to sound discrimination. There are many other suggested functions f the MEMs. The surface area of the tympanic membrane is about 6O mm2, whereas that of the oval window is only bout 3 mm2. The force of the sound on the tympanic membrane is transmitted (via the three ossicles) to the oval window nd the pressure of the sound (pressure = force per unit area) is thus about 20 times magnified. A tube, called ha ryngofympanic tube or Eustachian Tube emerges from the middle ear and opens into the nasopharynx. Thus, when his tuba is open, the middle ear cavity is in communication wilh the atmosphere However, in most of the time, the tube is losed. The Euslachian tube opens only during such acts like yawning and swallowing Conditions like severe nasal Ilergy and common cold can obliterate the nasopharyngeal opening of the Eustachian tube by causing swelling of the hucosal cells and now even swallowing fails to open the tube. In such conditions. 02 of the sir trapped inside the middle ar cavity is absorbed and The pressure wilhm The middle ear cavity falls. This causes unequal pressure on the two sides f the tympanic membrane causing the tympanic membrane to bulge inwards, resulting in ear pam and loss of heanng lasal decongesants cause prompt relief.