A model analysis of tensile stress in the toadfish vestibular membranes

Abstract

Background. A theoretical model analysis of stress in the vestibular membranes has identified a geometrical stress factor incorporating shape, size, and thickness that can be used to assess peak stress in the various chambers. Methods. Using published measurements of the toadfish vestibular membranes made during surgery, the geometrical stress factor can be evaluated for each chamber based on the model. Results. The mean geometrical stress factor is calculated to be the lowest in the semicircular canal (4.4), intermediate in the ampulla (6.0), and the highest in the utricle (17.4). Conclusions. The model predicts that substantial hoop stress disparities exist in the toadfish vestibular labyrinth. Stress is least in the semicircular canal, which therefore appears to be the structure with greatest stability. The utricle is found to be the most stress prone structure in the vestibular labyrinth and therefore appears to be the chamber most vulnerable to distention and potential modification.

Figure 1

Artist's depiction of a reconstructed human labyrinth.

Figure 2

Artist's depiction of a reconstructed vestibular labyrinth in the Oyster Toadfish (after Ghanem).

Figure 3

Model of the basic vestibular membranes (after Pender).

Figure 4

Normalized hoop stress in the oyster toadfish model. The breakout sections reflect the configuration of the membrane elements and indicate the attendant mean normalized stress levels in the different chambers.

Figure 5

Normalized stress levels in the toadfish vestibular membranes. Mean, maximum, and minimum individual values for each of the three vestibular chambers are shown graphically.