The effects of skin-tissue morphometry on the mechanical impedance of rat glabrous skin

Abstract

In this thesis, the mechanical impedance of rat glabrous skin was measured at two di erent locations: the digit and the sole in the hind paw, at two frequencies: 40 Hz and 250 Hz with amplitude of 61 m. The force (F), the velocity (v) and the phase di erence between them ( ) were measured to calculate the mechanical impedance components. Skin samples were also studied histologically from the same locations where the impedance measurements were obtained. On the microscope images, morphometrical measurements of the skin layers were performed. All mechanical impedance and morphometrical measurements were done in two di erent conditions: the normal and the epidermis-peeled condition. In the normal condition, two-way ANOVA showed that the e ect of the location on the resistance was marginally signi cant (p=0.056), whereas the frequency had no e ect (p=0.376). The e ect of the frequency on the modulus was found to be signi - cant (p=0.018); however, the e ect of the location on the modulus was not signi cant (p=0.684). In the normal condition, there was a signi cant correlation between the resistance and the stratum corneum thickness at 40 Hz in the sole and marginally in the digit (r=0.61, p=0.06 for the digit; r=0.94, p<0.0001 for the sole). In the peeled condition, at 40 Hz, the remaining epidermis thickness in the digit was signi cantly correlated with the resistance, the reactance and the modulus (r=0.91, p<0.001 for the resistance; r=0.80, p<0.01 for the reactance; r=0.90, p<0.001 for the modulus). No correlations were found at 250 Hz either on normal and peeled conditions. According to these results, the impedance was found to be largely governed by resistance. The resistance of the skin was a ected by the location and it was highly correlated with the stratum corneum thickness at 40 Hz. This suggests that stratum corneum may determine the mechanical properties of the skin at 40 Hz.|Keywords : mechanical properties of the skin, skin layers, skin histology.