The Follicular Cell in the Pars Distalis of the Dog Pituitary Gland: An Electron Microscope Study

The presence of follicular cells has been verified in the pars distalis of the dog pituitary gland through the use of electron microscopy. These cells are stellate; they extend cytoplasmic processes among parenchymal cells, and surround colloid-containing follicular cavities in some places. Around the cavities, apposed surfaces of adjacent follicular cells are connected with each other by prominent terminal bars and desmosomes. These cells project microvilli, as well as cilia in occasional cells, into the follicular cavity. A small number of granules, 150-200 m∧u in diameter, are sometimes contained in the cytoplasm subjacent to the follicular surface. (Endocrinology77: 1053, 1965)