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BIOLOGY FOR BEGINNERS 



ABSORPTION 



The chief digestive action of the bile is on the fats which it makes 

 into a milk-like emulsion to be absorbed by the lacteals. If it is 

 prevented from entering the intestine, over half of the fats eaten 

 are not absorbed. 



Another important function of the liver is the storage of excess 

 carbohydrate food, in the form of glycogen or liver starch which 

 the body may draw upon as a source of energy in emergencies. The 

 liver, then, excretes waste, secretes a digestive fluid, and stores food. 

 Pancreas. Lying between the lower side of the stomach and 

 the first fold of the intestine is the pancreas, whose secretion is by 



far the most important in pro- 

 ducing the chemical changes 

 of digestion. The pancreatic 

 fluid is strongly alkaline, and 

 contains three enzymes: 

 trypsin, amylopsin, and steap- 

 sin. 



The trypsin resembles pep- 

 sin and completes the digestion 

 of the proteids, changing them 

 into soluble peptones. The 

 amylopsin (like the ptyalin of 

 saliva) changes starch to sugar, 

 while the steapsin changes fats 

 to fatty acids, soluble soaps, 

 and glycerin, all of which are 

 easily absorbed. 



FIG. 121. Chart showing process The pancreatic fluid thus 



of absorption. completes the digestion of food 



after it has undergone the pre- 

 paratory steps of (1) cooking, (2) chewing, (3) salivary digestion, 

 (4) gastric separation, (5) gastric digestion. 



Absorption and Assimilation. The general purpose of digestion 

 is to put the foods in a soluble form so that they may pass through 

 the body's membranes by osmosis. 

 Absorption is the name given to the passage of digested food 



