316 



SALIVAEY GLANDS AND PANCREAS 



On entering the lobule the duct is immediately transformed 

 into the intercalary type ; in the pancreas there are no intralobu- 

 lar ducts lined by columnar striated epithelium as in the salivary 



glands. The intercalary ducts are very 

 slender tubules which are lined by low 

 columnar or flattened epithelium. Be- 

 cause of the absence of larger intra- 

 lobular ducts the intercalary portions 

 are relatively very long and much 

 branched. 



On approaching its termination the 

 lining cells of an intercalary duct are 

 still more flattened and often acquire 

 a considerable breadth. They pass into 

 the acini in a peculiar manner. In- 

 stead of offering a direct transition 

 from the duct epithelium to that of 

 the acinus the cells of the former fre- 

 quently appear as if telescoped into 

 the lumen of the acinus. Thus the 

 centro-acinar cells of Langerhans are 

 produced, and consequently the centro- 

 long intercalary ducts, which, after acinar cells correspond closely in ap- 



branching, end in the acini, x 344. .,-, ,-, ,, . . 



(After Maziarski.) pearance with those of the intercalary 



ducts. They seem to occupy the lumen 



of the acinus, and are only separated from the distal ends of the 

 acinar cells by the secretory capillaries which place the secreting 

 cells in communication with the lumen of the duct. The centro- 

 acinar cells are characteristic of the pancreatic acini. 



THE ACINI of the pancreas possess an irregular tubular form 

 with frequent alveolar dilatations. Their lining epithelium rests 

 upon a recticular basement membrane within which are thin 

 " basket cells." A delicate connective tissue stroma invests the 

 acini. 



The secreting cells are tall and irregularly columnar or pyra- 

 midal in shape. Their nucleus lies in the proximal third of the 

 cell and is surrounded by recticular or very finely granular cyto- 

 plasm. The cytoplasm 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 



FIG. 260. KECONSTRUCTION MODEL 



OF THE HUMAN PANCKEAS. 



The intralobular duct gives off 



