Abstract
Vocal cords obtained from 4 normal human adults, 2 human infants 3 months after birth and 6 adult Japanese monkeys were fixed in formalin and embedded in paraffin. Longitudinal and transverse sections were prepared, stained by the Elastica van Gieson method, and observed by light microscopy. Differences in the distribution of collagen fibers and elastic fibers between humans and monkeys were evaluated. The lamina propria mucosae of the monkey vocal cord was much thinner than that of the human adults or infants and had fewer collagen fibers and elastic fibers. The lamina propria mucosae of the human adult vocal cord consisted of a superficial layer poor in connective tissue, an intermediate layer rich in elastic fibers, and a deep layer rich in collagen fibers. The lamina propria mucosae of the monkey vocal cord consisted of a superficial layer relatively rich in collagen fibers and elastic fibers and a deep layer poor in these fibers. In the tunica muscularis of the human vocal cord, collagen fibers and elastic fibers were abundantly present between muscle fibers. The tunica muscularis of the monkey vocal cord was relatively lacking in these fibers. These findings suggest that the arrangement and distribution of collagen and elastic fibers in the lamina propria mucosae and the tunica muscularis of the human vocal cord are specific to humans and reflect the complicated vocal function in humans.
