The prenatal human submandibular gland: a histological, histochemical and ultrastructural study

The submandibular glands of 6 human fetuses, 13.5-16 weeks old, were studied using light and electron microscopic techniques. The developing gland at this stage consisted of a bush-like network of terminal buds (primitive acini) and primary ducts surrounded by a loose mesenchyme. Both components had a lumen which was surrounded by 1 or 2 layers of epithelial cells. Those cells adjacent to the lumen were attached by desmosomes but lacked well developed terminal bars. The cells were separated by an intercellular space, into which projected numerous microvilli. The cytoplasm of the epithelial cells contained the usual organelles with some cells containing large accumulations of glycogen granules. Serous granules and the luminal contents were both strongly PAS and AB positive. The function of this secretory material, at this stage of human development, is unknown. No mucus-like granules were observed. The terminal buds and primary ducts were surrounded by a well developed basal lamina and contained a few elongated cells which appeared morphologically as developing myoepithelial cells. Morphologically the development of the human submandibular gland, at 13.5-16 weeks of age, is roughly equivalent ot the developmental stage of the gland seen in the newborn rat or mouse. By birth, the human submandibular gland would likely reach a mature state, because there would be ample time remaining, in a normal gestation, for the maturation process to be completed.