犬声帯の粘弾性に関する基礎的研究
1981 年 27 巻 3 号 p. 530-554
詳細
1981 年 27 巻 3 号 p. 530-554
The mechanical properties of vocal fold were measured, taking its functional layer structure into consideration. The mechanical properties examined were (1) the YOUNG'S modulus,(2) the differential YOUNG'S modulus, and (3) the shear modulus and viscosity. Excised canine larynges were subjected to the present investigation.
(1) YOUNG'S modulus
The YOUNG'S modulus in the longitudinal direction was estimated to be in the order of 106-107 dyn/cm2 for the epithelium, in the order of 105-106 for the lamina propria and in the order of 104-105 for the resting muscle. This indicates that the tensile stiffness becomes smaller in the following order: the epithelium, the lamina propria, and the resting muscle.
(2) Differential YOUNG'S modulus
The ranges of the value of the differential YOUNG'S modulus became smaller in the order of the epithelium, the superficial layer of the lamina propria, the entire lamina propria, and the muscle. All the tissues showed a saturation effect at the elongation of 30 to 70 per cent. The value of the differential YOUNG'S modulus increased according to the increase in elongation. When the elongation was 0 per cent that is at the original length of the specimen, the differential YOUNG'S modulus was in the order of 105 for the epithelium, the superficial layer of the lamina propria and the entire lamina propria, whereas the modulus was in the order of 104 for the muscle. In the saturation renge, the differential YOUNG'S modulus of the epithelium and that of the superficial layer of the lamina propria were in the order of 108, the modulus of the entire lamina propria in the order of 107, and that of the muscle in the order of 106.
For the entire lamina propria, the differential YOUNG'S modulus in the transverse direction was estimated to be in the order of 104, when the elongation was 0%. When a transverse tension was given to the lamina propria, the tissue was torn off at 200 to 300 per cent of the original length without showing a saturation effect. Just before being torn off the differential YOUNG'S modulus was estimated to be in the order of 106.
(3) Shear modulus and shear viscosity
The elastic and viscous shear properties were measured at very low frequencies, i. e. approximately 0.1 Hz. In the present experimental conditions, the elongation of the muscule was approximately 60% and that of the lamina propria approximately 30%.
The value of the shear modulus of the muscle and that of the lamina propria were almost the same, being approximately (2-3) X105. The differential YOUNG'S modulus for those tissues at the same elongation was approximately five times as large as the shear modulus.
The value of the shear viscosity of the muscle was twice or three times as large as that of the lamina propria. For both tissues, the value was in the order of 104 P (Cpoise=dyn·s/cm2).
Generally, the visco-elastic properties of the high polymer depend on frequency and temparature. The viscosity decreases as the frequency increases. Therefore, during vibration in vivo condition, the viscosity of the vocal fold, especially that of the lamina propria, is assumed to become very low.
