[Embryological development of the chick tongue].

Evolutionary, structural, ultrastructural and cytochemical studies (PAS, alcian blue, toluidine blue, Ruthenium red) were performed in chick tongues 7 to 19 days development, with the aim of observing the histomorphological changes during growth and differentiation. At 7 days the tongue was covered by a flat epithelium without cornification, with four cell lines. As an axis was observed a central hyaline-cartilaginous skeleton surrounded by mesenchyma. Since 11 days appeared glandular buds and canalized cell cords united trough complexes. At 15 days the epithelial thickness increased remarkably. The subepithelial connective tissue, already notably differentiated, formed papillae. Glandular acini contained PAS positive, alcianophilic, metachromatic and positive ruthenium red substance. Ultrastructurally, glands showed clear cells, with decreased electronic density and organoids randomly distributed and dark cells having electrodense cytoplasm and more organized organoids. At 19 days the epithelium was cornified in the tongue anterior half. A net increment of glycoconjugates was detected in glands. These observations show: 1) lingual glands secrete mucins since 15 days of embryonic development; 2) the cornified anterior epithelium is the result of a genetic pattern and not of a later functional adaptation to the type of feeding (grain eating birds).