270 THE DIGESTIVE SYSTEM 



diverticulum is connected to the duodenum, rapidly proliferates 

 and forms the head of the gland and the terminal part of the 

 main duct. 



About the same time, a similar diverticulum grows out from 

 the dorsal surface of the duodenum to form the body and tail 

 of the gland. The ventral and dorsal diverticula approach 

 one another and become fused. Their ducts become con- 

 nected in such a way that the main pancreatic duct is formed 

 by the distal portion of the dorsal duct and the whole of the 

 ventral duct, and it therefore opens into the duodenum in 

 common with the bile duct. The proximal part of the dorsal 

 duct retains its own connexion with the duodenum and 

 persists as the accessory duct of the pancreas. A trace of 

 this developmental change may or may not persist in the 

 presence of a connexion between the accessory and the main 

 pancreatic ducts. 



Annular pancreas is a rare congenital anomaly. Normally, 

 the margins of the head of the pancreas overlap the medial 

 border of the second part of the duodenum both anteriorly 

 and posteriorly. These overlapping edges may become so 

 increased in extent that they meet one another at the lateral 

 border of the duodenum, and thus form a complete circle 

 round the gut. The condition may give rise to no symptoms 

 whatever, but, if the gland becomes the site of inflammatory 

 changes, serious obstruction of the duodenum will result. 



The Pancreatic Secretion contains three important enzymes, 

 which act on the proteid, the fatty and the carbohydrate 

 elements of the food. The flow of pancreatic juice commences 

 when the acid contents of the stomach are expelled into the 

 duodenum. In the presence of an acid medium, the duodenal 

 mucous membrane secretes a substance, termed secretin, 

 which becomes absorbed into the blood-stream and eventually 

 reaches the pancreas, where it causes a rapid flow of the 

 pancreatic secretion. It follows, therefore, that a diminution 

 in the acidity of the stomach contents is accompanied by a 

 diminution in the pancreatic secretion. Under these circum- 



