302 SECRETION 



through the substance of the gland to drain the 

 lobules by means of small ducts which open into it. 

 Increasing in size it reaches the neck, passes down- 

 ward, backward, and obliquely to the right, piercing 

 the muscular and mucous coat of the second portion 

 of the duodenum where it opens into the ampulla of 

 Vater, common to it and the bile duct; the latter opens 

 into the canal of the duodenum. 



The Structure of the Pancreas. It is similar in 

 structure to the salivary glands, consisting of numbers 

 of lobules, forming lobes, and all held together by 

 connective tissue. Each lobule contains one of the 

 branches of the main duct, which terminates in the 

 grape-like alveoli. The alveoli are lined by cylindric 

 cells, which differ in their appearance. They are 

 divided into a central set, in the end of the alveoli, 

 which are dark and granular, and a peripheral set, 

 in the outside of the former, which are clear. During 

 digestion the granular area becomes broader and the 

 cells show an increase in granules; in the interval of 

 rest following active digestion the clear zone increases 

 in width, showing an absence of granules. 



The Areas or Islands of Langerhans are groups of 

 globular cells arranged in columns situated between 

 the alveoli; surrounded by connective tissue, which 

 separates them from the alveoli and each other. The 

 connective tissue contains large, twisted, capillary 

 bloodvessels. These groups of goblet cells are supposed 

 to secrete an internal secretion, which is absorbed by 

 the blood and carried to the different tissues. Metab- 

 olism of the carbohydrates is interfered with, if any 

 diseased condition or removal of the pancreas takes 

 place. The secretion from the cells of the alveoli, 

 on the other hand, secretes the pancreatic juice. 



The pancreatic secretion 1 leaves the pancreas by 

 way of the duct of Wirsung; it is supposed to create 



1 See page 279 for action of pancreatic secretion during digestion. 



