The fine structure of the infundibulum and magnum of the oviduct of Gallus domesticus.

Abstract

The mucous membrane of the infundibulum and magnum of the hen's oviduct is modified for the receipt and fertilization of the yolk and the elaboration of the bulk of the solid material making up the white of the egg. The secreting surface is arranged in a series of ridges which are particularly elaborate in the neck region of the infundibulum. The surface is lined with columnar epithelial cells and there is a sub‐epithelial layer of tubular glands. There are two types of epithelial cell; ciliated, with little evidence of secretory activity; and granular, with the intracellular structure of a glycoprotein secreting cell. In the infundibulum the granular cells have electron dense granules and the tubular glands arise as invaginations from the epithelium of the deep crypts between the mucosal folds. The gland cells are structurally similar to the epithelial granular cells and have a characteristically large infranuclear granular endoplasmic reticular (GER) space filled with homogeneous material of low electron density, probably representing storage of synthesized protein. In the magnum the granules of the epithelial cells are of low electron density and fill the whole of the distended granular cell in the lower magnum, compressing the neighbouring ciliated cells.Three types of tubular gland cell are described in the magnum: Type A, filled with electron dense granules; Type B, filled with large masses of homogeneous material of low electron density; and Type C, occupied by GER cisternae together with a large and prominent Golgi area. The C cells, which are found in the magnum immediately after the passage of the egg, are regarded as the recovery phase of A cells which have discharged their granules on the passage of the egg. There is evidence that the dense granules of the A cells represent ovalbumin, the commonest protein of the egg white. The fibrous glycoprotein, ovomucin, with its large carbohydrate component, is probably produced by the granular cells of the magnum epithelium. There is a partial discharge of the secretion of the cells of the mucous membrane in response to the presence of the yolk. The nature of the secretion and the origin of some other components are discussed.