Comparative histology of the maculae flavae of the vocal folds.

A light and electron microscopic comparative investigation of the maculae flavae of the vocal folds was carried out on excised human and canine adult larynges. The structure and functions of human adult maculae flavae (HMF) were found to differ from those of canine adult maculae flavae (CMF). The maculae flavae were composed of fibroblasts, elastic and collagenous fibers, and ground substance in humans and canines. The density of fibroblasts in HMF was found to exceed that in CMF. Fibroblasts in HMF were stellate with processes or spindle-shaped, and the nucleus-cytoplasm (N/C) ratio was small. Rough endoplasmic reticulum and Golgi apparatus were well developed in the cytoplasm. Fibroblasts in CMF were oval, and the N/C ratio was large. Endoplasmic organs were poorly developed in the cytoplasm. Synthesized elastic and collagenous fibers were more numerous in HMF than CMF, and the density of both in HMF was much greater than that in CMF. Ground substance was more abundant in CMF than HMF. Apparently, CMF did not produce elastic and collagenous fibers in amounts sufficient to develop vocal ligaments. The HMF contributes to the formation of the vocal ligaments and the layered structure of human vocal folds.