Functional Histology of the Macula Flava in the Human Vocal Fold – Part 1: Its Role in the Adult Vocal Fold

Abstract

Objective: This study aims to clarify the role of the maculae flavae (MFe) in the human adult vocal fold mucosa (VFM). Methods: Our current results concerning MFe in the human adult VFM are summarized. Results: MFe were found to be composed of dense masses of vocal fold stellate cells (VFSCs) and extracellular matrices (EM), such as fibrous proteins and glycosaminoglycans, which are essential for the EM in the human VFM. VFSCs in the MFe demonstrated marked morphologic differences from conventional fibroblasts. They were irregular and stellate in shape and possessed slender cytoplasmic processes. They had well-developed intracellular organelles. A number of vesicles were present at the periphery of the cytoplasm. They constantly synthesized EM. The VFSCs possessed lipid droplets and stored vitamin A. VFSCs formed an independent cell category of cells in the human VFM. The VFSCs in aged adult MFe decreased their activity, and had abnormal metabolism. Conclusion: Human MFe including VFSCs seem to be involved in the metabolism of EM which are essential for the viscoelasticity of the lamina propria of the VFM, and to be responsible for maintaining the characteristic layered structure of the human VFM. Age-related changes in VFSCs were found to influence the metabolism of EM in the VFM.