Anatomic development of the oral and pharyngeal portions of the vocal tract: An imaging study

TLDR

Vocal tract growth is non‑uniform, with regional differences in anatomic maturation. The study quantified growth of oral and pharyngeal vocal‑tract segments in 605 individuals aged birth to 19 years. Researchers segmented the oral portion into lip thickness, anterior cavity length, oropharyngeal width, and VT‑oral, and the pharyngeal portion into posterior cavity length and nasopharyngeal length, then analyzed the data for growth trend, rate, and neural versus somatic growth type. The analysis revealed sex‑specific growth trends for all variables except anterior cavity length, with most vocal‑tract structures following a hybrid neural‑somatic growth pattern and vertical‑plane structures predominantly somatic, underscoring non‑uniform growth that contributes to pre‑pubertal acoustic differences.

Abstract

The growth of the vocal tract (VT) is known to be non-uniform insofar as there are regional differences in anatomic maturation. This study presents quantitative anatomic data on the growth of the oral and pharyngeal portions of the VT from 605 imaging studies for individuals between birth and 19 years. The oral (horizontal) portion of the VT was segmented into lip-thickness, anterior-cavity-length, oropharyngeal-width, and VT-oral, and the pharyngeal (vertical) portion of the VT into posterior-cavity-length, and nasopharyngeal-length. The data were analyzed to determine growth trend, growth rate, and growth type (neural or somatic). Findings indicate differences in the growth trend of segments/variables analyzed, with significant sex differences for all variables except anterior-cavity-length. While the growth trend of some variables displays prepubertal sex differences at specific age ranges, the importance of such localized differences appears to be masked by overall growth rate differences between males and females. Finally, assessment of growth curve type indicates that most VT structures follow a combined/hybrid (somatic and neural) growth curve with structures in the vertical plane having a predominantly somatic growth pattern. These data on the non-uniform growth of the vocal tract reveal anatomic differences that contribute to documented acoustic differences in prepubertal speech production.