THE DIGESTIVE SYSTEM 



243 



by the pancreas splits starch into monosaccharids. Another enzyme, 

 lipase or steapsin, when activated by enterokinase breaks fats into fatty 

 acids and glycerine. Another enzyme, ereptose or erepsin, splits pro- 

 teoses and peptones. The digestive activity of the pancreas is stimulated 

 through the endocrinal effect of secretions poured into the blood by the 

 intestinal glands when the acid chyme enters the intestine from the 

 stomach. 



Besides this digestive function, the pancreas acting as an endocrine 

 gland regulates the sugar metabolism of the body by means of the hormone 

 insulin. 



The histological structure of the pancreas strikingly resembles that of 

 the parotid gland, both being compound acinous glands divided into lobes 

 and lobules by connective-tissue septa which contain interlobular ducts, 



..--STOMACH 



DUCT OF SANTORIN 

 RSAL PANCREIAS 



DORSAL PANCREAS 



"VENTRAL R^NCREAS' 

 DUODENUM 



BILE DUCT WIRS UNO'S DUCT 



A. EARLIER STAGE. B. LATER STAGE. 



Fig. 227. — A and B, two stages in the development of the pancreas. The duct of 

 the dorsal pancreas, Santorini's duct, may degenerate in ontogenesis. The two gland 

 anlagen unite into a single organ in the adult. (Redrawn after Broman.) 



blood-vessels, and nerves. The acini of the pancreas, instead of being 

 hollow, contain central cells. 



Scattered irregularly among the acini of the pancreas are clusters of 

 lightly-staining cells. The area of each cluster in section is considerably 

 greater than that of a single acinus. These are the islands of Langerhans, 

 endocrinal organs which secrete insulin. (Fig. 289) 



Development of the Pancreas. Like the liver, the pancreas develops 

 from the endoderm. It is formed by the fusion of two separate out- 

 growths of the intestine, a ventral bilobed outpocketing from the bile- 

 duct, and a dorsal evagination of the intestine slightly anterior to that of 

 the liver. By the proHferation of the cells of these anlagen, two pan- 

 creases are formed. They secondarily unite, but retain usually the two 

 primary connexions with the intestine, the ventral becoming Wirsung's 

 duct and the dorsal Santorini's, the two connecting within the body of the 

 gland. The dorsal pancreas grows much faster than the ventral, and 

 forms the body and tail of the gland and part of the head. 



