Tympanic Lamella

Structure and/or Key Feature(s)

The basilar membrane is covered on its side facing the scala tympani by the tympanic lamella (or tympanic covering layer). The tympanic lamella tends to be thin underlying the pars acurata of the basilar membrane but thickens under the pars pectinata (Angelborg and Engstrom, 1974).

Cells of the tympanic lamella are spindle shaped and contain long processes at each pole. The cells are connected via desmosomes, however, spaces between cells can be large. This allows permeation of the perilymph in the scala tympani through the basement membrane to the organ of Corti. Additionally, the cells in the tympanic lamella at the base of the cochlea are more numerous, and so, there is less free space between the cells. Toward the apex of the cochlea, the cells become sparser (Angelborg and Engstrom, 1974).

Anatomical Relations

The tympanic lamella sits inferior to the basilar membrane.

Function

The tympanic lamella allows for the communication of perilymph of the scala tympani to the organ of Corti. Additionally, the cells of the tympanic lamella may play a defensive role in protecting the cochlea against infection. The fact that there are far more cells in the tympanic lamella situated in the base of the cochlea, which is the nearest part of the cochlea to the round window and the perilymphatic duct and the most likely site of microbial entry, suggests a possible defensive role (Angelborg & Engstrom, 1974).

References

Angelborg, C. & Engstrom, B. (1974) The Tympanic Covering Layer. An Electron Microscopic Study in Guinea Pig. Acta Otolaryngol, 77(319), 43-56.