ACTION OF THE PANCREATIC JUICE 125 



organ, often called the sweetbread, is an elongated race- 

 mose gland of a pinkish-yellow color lying along the 

 greater curvature of the stomach. The cells of this 

 gland secrete a digestive fluid called the pancreatic juice, 

 which they pour into a central duct. This duct joins the 

 bile duct close to its intestinal opening, and bile and pan- 

 creatic juice mingle and enter the intestine by the com- 

 mon opening. (See Fig. 42.) 



Pancreatic juice. — This is a watery secretion which 

 contains three very important enzymes. One (trypsin) 

 changes proteid to peptone, one (amylopsin) changes starch 

 to sugar, and the third (steapsin) acts upon fats. 



Digestion in the Small Intestine. 



The partly digested food or chyme which is forced from 

 time to time through the pyloric orifice of the stomach is 

 now ready for the action of the various digestive fluids of 

 the small intestine. (See Ex. XXXVIII.) The digestive 

 action which takes place in the intestine is, therefore, due 

 to the combined action of three digestive fluids, pan- 

 creatic juice, bile, and intestinal juice. Rhjrthmic peris- 

 taltic movements of the muscle walls of the intestine 

 keep the contents of the intestine in constant motion, 

 and thus mix them with these combined juices. 



Action of the pancreatic juice. — This juice owes its 

 digestive action to its three enzymes, trypsin, amylopsin, 

 and steapsin. 



Trypsin. (See Ex. XXXVIII. , a.) Trypsin is a more 

 powerful enzyme than pepsin and, unlike that, acts best 

 in an alkaline medium. Like pepsin, its action is affected 



