[Pliability of vocal fold mucosa in relation to the location of subglottic mucosal upheaval during phonation].
Mucosal pliability was measured in 23 excised larynges, 19 canine and four human, at the three portions of the vocal fold, namely the midline, the anterior 1/4 and the posterior 1/4. The pliability at the midline showed a greater value than those at the other two portions. The free edge of the vocal fold showed a maximum pliability which gradually diminished toward the tracheal side and reached a minimum 3mm from the free edge of the fold. An increase in vocal fold tension resulted in lowering of mucosal pliability at all measured points and the point of minimal pliability shifted toward the oral side. The point of minimal pliability moved toward the tracheal side with direct electrical stimulation of the thyroarytenoid muscle (TA). Both pliability measurement and observation of mucosal vibration from the tracheal side using high speed cinematography or stroboscopy were performed on eleven of the excised canine larynges. The mucosal upheaval occurred at the point around which pliability was minimal. An increase in vocal fold tension resulted in an upward shift of the mucosal upheaval which occurred slightly below the point of minimal pliability. Electric stimulation of the TA resulted in a downward shift of the mucosal upheaval which occurred in accordance with the point of minimal pliability. Histological examination of the canine larynges revealed that the lamina propria became increasingly thin toward the point around which pliability was minimal and at which the mucosal upheaval occurred. At this point, the muscle layer approximated the epithelial layer with disappearance of the deep layer of the lamina propria. The point shifted to the oral side following an increment in vocal fold tension, while the point moved toward the tracheal side following contraction of the TA. Pliability of the vocal fold is minimal at the point around which the deep layer of the lamina propria disappears and the mucosal upheaval occurs.
Kadota
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Y
Department of Otolaryngology, School of Medicine, Ehime University.
D000818:Animals; D004285:Dogs; D006801:Humans; D007820:Laryngeal Mucosa / Q000502:physiology; D010699:Phonation / Q000502:physiology*; D018583:Pliability; D014827:Vocal Cords / Q000502:physiology*