374 



HOW FOOD IS PREPARED FOR BODY USE 



remain for some time in a milky emulsion. If this emulsion is 

 examined under the microscope, it will be found to be made of 



millions of little droplets of 

 fat, floating in the liquid. 

 The presence of the caustic 

 soda helped the forming of 

 the emulsion. Pancreatic fluid 

 emulsifies fats and changes 

 them into fatty acids and 

 soft soaps. Fat in these forms 

 can be absorbed. The above 

 changes are brought about 

 by three enzymes : amylase 

 (am'i-las), which breaks down 

 starches to simpler sugars ; 

 trypsin (trip'sm), which, 

 working with other enzymes 

 of the small intestine, breaks 

 protein into amino acids ; 

 and lipase (lip'as), which 

 breaks the fats into fatty acids and glycerin. These fatty 

 acids become soap when mixed with the alkaline material in 

 the intestinal juice. 



Conditions in which the pancreas does its work. The secre- 

 tion of the pancreatic juice is brought about by the action of a 

 hormone called secretin. This substance, which is formed in some 

 of the cells lining the small intestine just below the pylorus, is 

 released into the blood at the time food passes from the stomach 

 through the pylorus. This food is acid, and the acid, on touching 

 the lining of the small intestine, causes the formation of secretin 

 in its walls. This secretin passes into the blood and stimulates 

 the pancreas and liver to release their fluids. This is an example 

 of hormone control. 



Milk, a form of emulsion, as seen under the 

 microscope. The fat globules appear in groups. 

 The circle shows one group of globules highly 

 magnified. 



Self-Testing Exercise 



The pancreatic fluid changes (1) to 



(3) to (4) (5), and 



(6) 



...(2); 

 into . . 



(7) 



