THE SECRETING GLANDS 299 



by the liver cells to the intestinal canal and gall- 

 bladder. 



The Functions of the Liver. (1) The liver secretes 

 the bile; (2) produces and stores glycogen until needed 

 to aid in the nutrition of the tissues; (3) aids in the 

 formation and excretion of urea. The production of 

 bile and its physiologic actions have been described. 

 (See Part Played by the Bile in Digestion, page 281.) 



The Formation and Function of Glycogen. Glycogen is 

 derived from the dextrose resulting from the action of 

 the intestinal juices upon the food. It represents the 

 products of the carbohydrates absorbed as dextrose 

 and carried in the blood by the branches of the portal 

 vein to the liver, when it undergoes chemical changes, 

 due to the action of the liver cells, and is deposited 

 as a non-diffusible body. Glycogen is stored in the 

 liver until needed by the body tissues. 



The Formation of Urea. Urea is believed to be 

 produced and excreted by the liver cells. It is formed 

 from ammonium salts, as carbonate, lactates, which 

 are formed as a result of tissue metabolism upon the 

 proteins contained in the food we eat, and these 

 salts are absorbed from the tissues or from the intes- 

 tines, and conveyed by the blood to the liver cells, 

 where they are converted into urea and eliminated as a 

 waste product. It is excreted by the kidneys and 

 found in the urine. 



The Gall-bladder. This is a pear-shaped sac lying 

 in the impression of the right lobe of the liver. It is 

 the reservoir for the bile. It is 4 inches long and 1J 

 inches broad, holding 8 to 12 drams, and is held in 

 place by areolar tissue and the peritoneum. Its 

 relations are as follows: Above, liver; below, ascending 

 duodenum, pyloric end of stomach, hepatic flexure of 

 colon; in front, abdominal wall (ninth or tenth costal 

 cartilages) . 



The hepatic duct is formed by the junction at an 

 obtuse angle of a branch from each lobe of the 



