An attempt was made to create serous effusions in the middle ear cavity of the guinea pig by obstructing the eustachian tube. Histologic sections, however, indicated that only an incomplete occlusion of the tube was present. Among the 11 animals used, six developed a serous or seromucous effusion. The predominant findings were: (1) the loss of ciliated cells in the early stages (eight days) and (2) an increase in the number of dark-granulated cells. The thickening of the submucosal layer was due to an increased cellularity with the deposition of dense cottony spheres in the matrix. These densities are similar to calcium crystals found in early ossification centers. There was also an increased cellular infiltration consisting primarily of polymorphs, but also including round-cell types and macrophages. No evidence of bacterial invasion was found.
Lim D, Hussl B. Tympanic Mucosa After Tubal ObstructionAn Ultrastructural Observation. Arch Otolaryngol. 1970;91(6):585–593. doi:10.1001/archotol.1970.00770040815017
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