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Embryonic middle ear mesenchyme disappears by redistribution
J Piza1, C Northrop, R D Eavey
1Department of Pathology, Hospital Nacional de Niños, Universidad de Costa Rica, San José.
The Laryngoscope
|September 17, 1998
Summary
Embryonic middle ear mesenchyme redistributes to line growing cavities in both opossums and humans. This explains the apparent disappearance of mesenchyme in the developing ear, regardless of gestational environment.
Area of Science:
- Developmental biology
- Anatomy
- Histology
Background:
- The fate of embryonic middle ear mesenchyme post-gestation has been unclear.
- Previous studies suggested mesenchyme disappears by redistribution in human neonatal ears.
- This raises questions about the influence of the gestational environment on mesenchymal behavior.
Purpose of the Study:
- To investigate the behavior of embryonic middle ear mesenchyme in a marsupial model.
- To compare opossum data with existing human neonatal temporal bone data.
- To determine if gestational environment impacts mesenchymal behavior.
Main Methods:
- Histologic analysis of opossum temporal bones (20-36 days old).
- Calculation of middle ear air cavity (VAC), bone cavity (VBC), mesenchyme volume (VM), and % mesenchyme (%M).
- Regression analysis comparing opossum and human neonatal (0-30 days old) data.
Main Results:
- Both VAC and VBC increased with body growth in opossums and humans.
- VM remained constant in both species regardless of body length.
- %M decreased inversely with increasing ear size in both opossums and humans.
Conclusions:
- Embryonic mesenchyme does not disappear but redistributes to line enlarging middle ear cavities.
- This redistribution occurs in both opossums and humans.
- Findings are consistent across different gestational environments (intrauterine vs. extrauterine).