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.

Functional Histology of the Macula Flava in the Human Vocal Fold – Part 2: Its Role in the Growth and Development of the Vocal Fold

“…On the basis of the results of our current study, human MFe located at both ends of the VFM are inferred to be involved in the metabolism of EM, essential for the viscoelastic properties of the lamina propria of the human adult VFM [23] . Human adult MFe are inferred to be responsible for maintaining the characteristic layered structure of the human VFM [23] .…”

“…Human adult MFe are inferred to be responsible for maintaining the characteristic layered structure of the human VFM [23] . Human adult MFe are also considered to be an important structure in the aging of the human VFM [23] .…”

Histopathologic Investigations of the Unphonated Human Child Vocal Fold Mucosa

“…On the basis of the results of our past studies, the MFe have been inferred to be involved in the metabolism of extracellular matrices and are considered to be an important structure in the growth, development, and aging of the human vocal fold mucosa. 1,2 VFSCs, which are interstitial cells with a star-like appearance and are dense in the human MFe, were discovered in our previous studies. 3,9,[16][17][18][19] The VFSCs possess lipid droplets and store vitamin A.…”

“…Our previous studies inferred that the VFSCs in the MFe form an independent cell category, which should be considered a new category of cells and are involved in the metabolism of extracellular matrices in the human vocal fold mucosa. 1,2 Growth and development of the layered structure of the human vocal fold mucosa as a vibrating tissue Human adult vocal folds have a layered structure with a vocal ligament and Reinke's Space. 10,20 The layered structures are very important in vibration and are required for phonation.…”

“…1,2 We also hypothesize that the tension (mechanical force) caused by phonation (vocal fold vibration) after birth stimulates VFSCs to accelerate production of extracellular matrices and form the characteristic layered structure of the human vocal fold mucosa. [3][4][5][6] Mechanical stresses are ever present in the cellular environment, and such forces affect cellular signaling and function.…”