ABSORPTION 



137 



coc 



pillar^ 



cell 



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 change back into fat 

 particles. This fluid or lymph 

 then passes into the lacteal s 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 The vUlus is adapted for absorption. A network of 



A* j.1, Ul J microscopic blood vessels absorbs digested food from the 



portion 01 the blOOd. small mt estine. A lymphatic, known as a lacteal, runs 



The adaptations of the through the center and tekes to the digested fat ' 

 small intestine are so adequate that practically everything dif- 



WH. FITZ. AD. BIO. 10 



