397 



THE PANCKEAS 



upon a reticular basement membrane within which are thin M 

 cells/ A delicate connective tissue stroma invests the acini or alveoli. 

 The secreting cells are tall and irregularly columnar or pyramidal 

 in shape. Their nucleus lies in the proximal third of the cell and is 

 surrounded by reticular or very finely granular cytoplasm. The cyto- 



't *rf^ 



FIG. 369. ACINI OF THE HUMAN PANCREAS. 



The acinus at a is connected with an intercalary duct, cut in tangential section, 

 and occupying the center of the figure. Hematein and eosin. Photo. X 950. 



plasm of the inner zone of the cell, on the other hand, is filled with 

 coarse zymogen granules whose number is dependent upon the activity 

 of the gland. During fasting the granules accumulate until eventually 

 they almost completely fill the cell, but during digestion they disappear 

 with the discharge of the secretion, the width of the granular /one 

 gradually decreasing, that of the non-granular fibrillar basal zone being 

 correspondingly enlarged (Figs. 371, A and B). 



