Morphogenesis of the palate in normal human embryos with special emphasis on the mechanisms involved This investigation was supported by research grant HD 00178 from the National Institute of Child Health and Human Development and a National Science Foundation Summer Undergraduate Research Fellowship (GE-6283) to K. F.

Abstract

The aim of this study was to re-evaluate the classical description of fusion as the closure mechanism of both the hard and soft palates in normal human embryos. Does the soft palate develop by a posterior continuation of shelf apposition, epithelial lamination and disintegration, and by mesenchymal cell fusion as described for the hard palate? Or does the soft palate develop by proliferation and migration of subepithelial mesenchymal growth centers at the posterior edge of the fused hard palate so that the early furrow which separates the two primordial processes of the soft palate is progressively obliterated by mesenchymal merging at the furrow base? Observations of human embryos prior to, during, and after palatal closure (7–12 wks, 18–75 mm C-R length) indicated (1) an anteroposterior gradient of palatal closure beginning at the primary palate and (2) epithelial fusion remnants found only in the hard palate regions. These observations suggest that the soft palate develops by a displacement of epithelium by mesenchymal merging rather than by epithelial fusion of the entire secondary palatine processes.