Differentiation of human anterior hypophysial cells during fetal life.

This paper deals with cell differentiation in the anterior hypophysis of the human fetus, as may be stated by electronmicroscopy. In the 9 cm fetus the greater number of cells are devoid of granules; this was the reason for their being considered as nondifferentiated cells. A small number of cells however contain granules which vary from cell to cell in number and size and may be considered as cells with different functions. Usually the granules secreted within the same cell have very close diameters. The number of such cells increases with the age of the fetus; thus, in 170 mm fetal length there remain very few nondifferentiated cells. Some cells have their granules located centrally, while in others they are closer to the cell membrane, suggesting that the product of cell secretion is extruded in the nearby lumen of capillaries. The shape of the cells, their location, as well as the features of the cell organelles are similar to those described for adults, but in the fetus they are proportionally fewer. The electronmicroscopic pattern does not seem to be a sufficient criterion for the specification of the type of cells, except ACTH-MSH secreting cells.