Morphogenesis of the Inner Ear at Different Stages of Normal Human Development

Abstract

This study examined the external morphology and morphometry of the human embryonic inner ear membranous labyrinth and documented its three-dimensional position in the developing embryo using phasecontrast X-ray computed tomography and magnetic resonance imaging. A total of 27 samples between Carnegie stage (CS) 17 and the postembryonic phase during trimester 1 (approximately 6-10 weeks after fertilization) were included. The otic vesicle elongated along the dorsoventral axis and differentiated into the end lymphatic appendage and cochlear duct (CD) at CS 17. The spiral course of the CD began at CS18, with anterior and posterior semicircular ducts (SDs) forming prominent circles with a common crus. The spiral course of the CD comprised more than two turns at the postembryonic phase, at which time the height of the CD was evident. A linear increase was observed in the length of anterior, posterior, and lateral SDs, in that order, and the length of the CD increased exponentially over the course of development. Bending in the medial direction was observed between the cochlear and vestibular parts from the latero-caudal view, with the angle decreasing during development. The position of the inner ear was stable throughout the period of observation on the lateral to ventral side of the rhombencephalon, caudal to the pontine flexure, and adjacent to the auditory ganglia. The plane of the lateral semicircular canal was approximately 8.08-14.68 with respect to the cranial caudal (z-)axis, indicating that the orientation of the inner ear changes during growth to adulthood. Anat Rec, 298:2081Rec, 298: -2090Rec, 298: , 2015. V C 2015 Wiley Periodicals, Inc.Abbreviations used: CD 5 cochlear duct; CS 5 Carnegie stage; IEL 5 Inner ear length; MRI 5 magnetic resonance imaging; PCXT 5 phase-contrast X-ray computed tomography; PE 5 postembryonic phase

Novel imaging techniques to study postmortem human fetal anatomy: a systematic review on microfocus-CT and ultra-high-field MRI

“…Thayyil et al [14] was able to achieve full body datasets with a reasonable resolution of 200-μm isotropic voxel size in 70 min. This is considerably shorter than other groups that needed 20 to 78 h to visualize the development of the inner ear with an isotropic voxel size of 35 to 55 μm [42,43]. This is due to the fact that reduction in voxel size by a factor 2 in 3-dimension results in a reduction in signal by a factor 2 × 2 × 2 = 8.…”

Formation of the Periotic Space During the Early Fetal Period in Humans

“…A greater understanding of the development of the perilymphatic space may facilitate insight into the mechanism underlying such diseases. In our recent study, we observed the formation of a membranous labyrinth during the embryonic and early fetal period (Toyoda et al, 2015). The membranous labyrinth was already differentiated into three sections, that is, the CD, SDs, and vestibule, in samples representing the end of the embryonic stage, which suggest that the membranous labyrinth increases in size during the fetal period.…”

3D Analysis of Human Embryos and Fetuses Using Digitized Datasets From the Kyoto Collection

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