§ 2.123 ENDOCRINE GLANDS FROM ECTODERMAL EPITHELIUM 43 



control the blood supply to the neural lobe and the pars distalis, 

 but do not appear to make any contact with the secretory cells. 



There are no nerves to the pars intermedia in mammals, thou^^li 

 secretions from this part appear to be under nerve control in fish 

 and amphibia (§ 4.3). 



The PARS DISTALIS of the adenohypophysis contains at least 

 three distinct types of cells: chromophobe (gamma) cells which 

 have no stainable granules in their cytoplasm and seem to have no 

 secretory function, though they may give rise to one or both of 

 the secreting types ; basophil cells, which contain secretory granules 

 of glycoprotein that stain blue by the Mallory or Azan trichrome 

 methods, and acidophil cells, which contain phospholipid granules 

 that stain selectively by an acid haematin method. The last two 

 types can also be distinguished by staining with safranine-acid 

 violet (cf. Maximow and Bloom, 1942, Fig. 261.-2) and show 

 changes which are clearly associated with the secretory activity 

 of the gland. For some time it was claimed that only these two 

 types of secreting cells could be identified histologically although 

 the gland was known to secrete six or seven distinct hormones; 

 but recently more sensitive tests have been applied and tentative 

 subdivisions of the two types have been proposed (Table 4) ; 

 further details have recently been summarized by Pickford and 

 Atz (1957). 



The PARS TUBERALis has not been studied so fully but appears to 

 consist of columns of cells separated by blood spaces, and to be 

 closely similar to the adenohypophysis in appearance. A secretory 

 activity has only been claimed for it in some fish and amphibians 

 (§3.23). 



The PARS INTERMEDIA may consist of cells with basophil granules 

 and non-granular cells that form follicles filled with a colloid, 

 similar in appearance to that in the thyroid gland but containing 



the PARS TUBERALIS (PT), from which loops penetrate deeply into 

 the median eminence and can receive neurosecretions. These 

 vessels join again to give the hypophysial portal system (HP) 

 which breaks up into the secondary venous plexus (VS) in the 

 PARS DISTALIS (PD) of the adenohypophysis. This part also receives 

 blood directly from the lower hypophysial arteries (HY=^). (Original, 

 based on Scharrer and Scharrer, 1954^, and Harris, 1955). 



