Ultrastructure of the adenohypophysis in the domestic pig (Sus scrofa domestica). Part I: Cells of the pars anterior.

In the hypophyses of 46-79 days old pig embryos three groups of cells were separated; one group constitute non-differentiated cells, second, cells becoming differentiated, and third, seven types of differentiated cells. Probably three of these types are equivalent to the secretory cells STH, TSH, and FSH, and one type of them--to the cells described in the hypophysis of adult vertebrates as stellate cells or follicular cells. Possibly only one type of the differentiated cells has the ability to liberate a secretion into the intercellular space; however, the type of a hormone produced by these cells has not been described yet. It seems that in the studied stages of development of the hypophysis production and accumulation of hormones takes place in secretory cells, while the secretion of these hormones begins later than in periods of development investigated by us.