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Development of the endolymphatic sac in chick embryos, with reference to the degradation of otoconia
T Yoshihara1, H Kaname, N Narita
1Department of Otolaryngology, Tokyo Women's Medical College, Japan.
Insights
The chick embryo endolymphatic sac may degrade otoconia and remove calcium. This study observed otoconia-like bodies within the sac, suggesting a role in calcium homeostasis.
Area of Science:
- Developmental Biology
- Otolaryngology
- Cell Biology
Background:
- The endolymphatic sac plays a crucial role in inner ear fluid balance and calcium homeostasis.
- Understanding its developmental morphology is key to elucidating its functions.
Purpose of the Study:
- To investigate the ultrastructural changes and potential functions of the endolymphatic sac in chick embryos.
- To explore the presence and fate of otoconia-like bodies within the endolymphatic sac during development.
Main Methods:
- Light and electron microscopy were employed to examine the endolymphatic sac of chick embryos from embryonic day 7 to post-hatching.
- Morphological analysis focused on epithelial cell characteristics, microvilli, intercellular spaces, and the presence of otoconia-like bodies.
Main Results:
- Early in development (stage 30-31), the endolymphatic sac epithelium was cuboidal to columnar with well-developed microvilli and wide intercellular spaces.
- Otoconia-like bodies were frequently observed in the endolymphatic space, with intracytoplasmic phagosomes containing them being rare.
- After stage 37, these bodies diminished in number and size, becoming ultrastructurally similar to otoconia in macular organs.
Conclusions:
- The endolymphatic sac of chick embryos may function in the degradation of otoconia.
- The observed changes suggest a role in the removal of calcium from otoconia, contributing to calcium homeostasis.
Abstract:
The endolymphatic sac of chick embryos (from embryonic day 7 to 1-day-old chicks) was studied light- and electron-microscopically. At stage 30-31 (embryonic day 7-7.5), the epithelial cells of the endolymphatic sac were cuboidal to columnar in shape. Microvilli were relatively well developed. The intercellular space was wide. In the endolymphatic space of the endolymphatic sac, varying shapes and sizes of otoconia-like bodies were often observed. Intracytoplasmic phagosomes containing these bodies were rarely found. After stage 37 (embryonic day 11), otoconia-like bodies in the endolymphatic sac decreased in number and size. They were almost the same as the otoconia in the macular organs, ultrastructurally. These findings indicate that the endolymphatic sac of the chick embryos may possess the function of otoconial degradation and removal of calcium from otoconia.