HYPOPHYSEAL MORPHOLOGY 



217 





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Fig. 3.28. Electron micrograph showing a th.yrotroph from the anterior pituitary of a young 

 adult male rat. The nucleus (A') and cell membranes (cm) are indicated. The irregular 

 contour characteristic of thyrotrophs is illustrated in the angular shape of this cell. 



In electron micrographs thyrotrophs can be distinguished by virtue of the size of their 

 secretory granules which are smaller (maximal diameter ca. 100 iu/m) than those in any 

 other type of anterior lobe cell (Farquhar and Rinehart, 1954b). In this cell the secretory 

 granules are found, for the most part, lined up along the cell membrane. 



As seen in this cell, the endoplasmic reticulum (er) of thyrotrophs is generally present 

 in the form of small vesicular profiles with occasional elongated (cisternal) profiles. The 

 mitochondria (?n) usually occur in the form of short rods and show a background matrix 

 which is much less dense than the internal matrix of gonadotroph mitochondria (see Figs. 

 3.29 and 3.30). A group of vacuoles of the Golgi complex (G) can also be distinguished 

 in the cytoplasm of the thyrotroph. 



The thyrotroph is virtually surrounded by acidophils of the growth hormone type. The 

 cytoplasm of these cells is labeled A. The size of their secretory granules (maximal diameter 

 ca. 350 m/i) can be contrasted with the smaller thyrotrophic granules. X 10.000. 



the rest of the cytoplasm. The PAS reaction 

 shows that this is due to a greater concen- 

 tration of glycoprotein granules in the en- 

 closed cytoplasm. The appearance of the 

 darkly stained cytoplasm within the nega- 

 tive image of the Goki body has not always 



been interpreted correctly and some investi- 

 gators have mistaken it for an early stage 

 of hyalinization. 



Severinghaus (1932, 1933) reported that 

 in the rat the Golgi apparatus of the cells 

 of the acidophil class has a different form 



