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Epithelial distribution in the human fetal larynx
1Electron Microscopy UNit, Institute of Laryngology and Otology, London, England.
Summary
Squamous epithelium is a normal finding in the fetal larynx, extending into the subglottic region. This suggests these areas are not always due to irritation or trauma.
Area of Science:
- Human fetal development
- Laryngeal histology
- Epithelial biology
Background:
- The subglottic larynx in neonates, infants, and adults has shown squamous metaplasia.
- The origin and normalcy of this squamous epithelium remain debated.
Purpose of the Study:
- To investigate the distribution of squamous and ciliated respiratory epithelia in the human fetal larynx.
- To clarify the nature of squamous epithelium in the subglottic region.
Main Methods:
- Light microscopy
- Scanning electron microscopy
- Transmission electron microscopy
- Analysis of ten midtrimester human fetal larynges.
Main Results:
- Both squamous and ciliated respiratory epithelia were present in the supraglottic, glottic, and subglottic regions.
- Significant downward extension of squamous epithelium from the glottis into the subglottic area was observed.
- A broad transition zone with coexisting epithelial types was identified in the subglottic region.
Conclusions:
- The presence of squamous epithelium in the nonglottic larynx appears to be a normal developmental feature.
- The term 'squamous metaplasia' may not be appropriate for these findings in the adult larynx, as they may represent normal histology.