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Histological development of stapes footplate in human embryos
Insights
The human stapes footplate develops early in gestation, forming by 50mm embryo length. Understanding this normal development is key to identifying causes of congenital middle ear anomalies.
Area of Science:
- Embryology
- Otolaryngology
- Developmental Biology
Background:
- The development of the human stapes footplate is crucial for hearing.
- Congenital anomalies of the stapes footplate can lead to hearing loss.
Purpose of the Study:
- To investigate the normal developmental timeline of the human stapes footplate.
- To correlate developmental stages with morphological changes in the stapes.
Main Methods:
- Analysis of serial sections from 35 Japanese embryos (6th to 32nd week).
- Light microscopy examination of 18 embryos (3.5mm to 105mm crown-rump length).
- Focus on the lamina stapedialis and its fusion with the annular stapes.
Main Results:
- Primordial lamina stapedialis observed in 16mm embryos.
- Complete formation and fusion of the lamina stapedialis by 35mm embryos.
- Adult stapes morphology, including rim and annular ligament, present in 50mm embryos.
Conclusions:
- Findings support the dual origin theory of footplate development.
- Teratogenic agents may impact any developmental stage, causing anomalies like congenital footplate fixation or oval window absence.
Abstract:
Normal development of the human stapes footplate was investigated in serial sections by light microscopy. Materials were obtained from 35 Japanese embryos from the 6th to 32nd week of embryonal age. Eighteen embryos up to 16 weeks of age (3.5mm to 105mm in crown-rump length) were examined, focusing particularly on the lamina stapedialis of the otic capsule. The present study showed that primordial formation of the lamina stapedialis appeared in 16mm embryo and that the lamina was completely formed and fused to the base of the annular stapes in a 35mm embryo. In a 50mm embryo, the adult form of stapes was found with a rim and annular ligament. The results, therefore, seemed to essentially agree with the theory of dual origin and development of the footplate proposed by Cauldwell and Anson, and teratogenic agents might affect any stage of the process producing anomalies, including congenital footplate fixation, congenital absence of the oval window and calcification of the annular ligament.