| Description |
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The inferior portion of the right middle ear contains a serosanguinous fluid. Note the streak of interstitial hemorrhage along the handle of the malleus.
If the surrounding atmospheric pressure is lowered (e.g. during ascent), the pressure within the middle ear cleft rises in relation to the atmospheric pressure. When this occurs, the eustachian tube will open passively to allow the flow of air from the middle ear into the nasopharynx.
If the surrounding atmospheric pressure is raised (e.g., during descent), the pressure within the middle ear will be lowered in relation to the atmospheric pressure. Pain in the ear is usually experienced as the increased atmospheric pressure pushes the eardrum medially. When this occurs, the eustachian tube must be opened actively by swallowing or Valsalva's maneuver in order to allow the entry of air from the nasopharynx into the middle ear with consequent equalization of the transtympanic pressure differential. When the pressure differential exceeds 90 mm Hg, the soft tissues near the opening of the eustachian tube are forced into its lumen and active opening of the tube is no longer possible (a locked eustachian tube). |
