Development of the human true vocal fold: depth of cell layers and quantifying cell types within the lamina propria.

OBJECTIVES

We sought to further describe the development of the 3-layered human vocal fold in children and to quantify macrophage and myofibroblast concentrations in each layer.

METHODS

We used an optical analysis software package to examine 8 longitudinally sectioned human vocal folds that had been fixed in formalin (ages 2 days to 14 years).

RESULTS

The 2-day-old vocal fold contained only a monolayer of cells. This became a bilayer by 5 months, and a trilayer began to become evident by 7 years. The percent of total depth represented by the superficial layer of the lamina propria (SLP) gradually decreased with age. The SLP made up 22% of the total lamina propria by age 7 years; this percentage approximates that in the adult vocal fold. Macrophages and myofibroblasts were predominately found in the SLP, and began to be apparent by 11 months of age.

CONCLUSIONS

These results help describe the development of human voice and may have implications as to when phonosurgical therapy can be considered for children.