ABSORPTION 



137 



..capillary 



eSmucus cell 



^-lacteal 



channel called a lacteal. The spaces among the capillaries, lac- 

 teals, and epithelial cells are filled with fluid known as lymph. 

 The digested food is absorbed 

 by osmosis through the epithe- 

 lial cells of the villi. These villi 

 cells exert a selective action, per- 

 mitting only the passage of cer- 

 tain materials. The process of 

 osmosis here is an active not a 

 passive one. Some soluble salts 

 are readily absorbed, while 

 others like tartrates, citrates, 

 and calcium salts cannot pene- 

 trate the epithelial cells. Fatty 

 acids, glycerol, and soaps enter 

 the epithelial cells, and during 

 the process of passing through 

 them are changed back into fat 

 particles. This fluid or lymph 

 then passes into the lacteals and 

 through other lymphatics, 

 leading from the lacteals, 

 and eventually drain into 

 the blood system. The 

 amino-acids, simple sugars, 

 salts, and water pass di- 

 rectly from the epithelial 

 cells of the intestine into 

 the capillaries and thus 

 become part of the liquid 

 portion of the blood. 



The adaptations of the 

 small intestine are so adequate that practically everything dif- 



The villus is adapted for absorption. A network of 

 microscopic blood vessels absorbs digested food from the 

 small intestine. A lymphatic, known as a lacteal, runs 

 through the center and takes in the digested fat. 



WH. FITZ. AD. BIO. 



10 



