Goblet cells in the developing rhinopharynx and pharynx.

In 60 foetuses and prematures, ranging in age from the 10th to the 30th menstrual week, the entire mucous membrane from the rhinopharynx and pharynx was removed and stained in toto with PAS-alcian blue, PAS, and osmium whole-mount methods. The development, spread, and density of goblet cells as well as the differentiation of the epithelium were studied. Goblet-cell development started in the 12th week, 3-4 weeks later than the development of ciliated cells, below the tubal orifice. Thereupon, goblet cells gradually spread behind the tubal orifice, towards the roof and further on to the nose. Thus, by the 17th week goblet cells and ciliated cells are present throughout the rhinopharynx and in the upper half of the pharynx. In the lower half of the rhinopharynx and upper part of the pharynx as well as in the posterior wall, the density is fairly low during the first weeks, and later it becomes even lower. In these sites the epithelium differentiation into startified squamous and transitional epithelium. In the roof of the rhinopharynx and in the fossa of Rosenmüller the density increases steadily, and in these sites respiratory tract epithelium is present. Transformation of the epithelium, which originally contains ciliated cells and goblet cells, into startified squamous epithelium and transitional epithelium is instituted at an early stage of development and continues throughout, but possibly it is promoted postnatally by mechanical contact between the walls.