THE ABDOMEN 



789 



Goblet CeU 



pancreatic duct has to be noted. At the junction of the inner 

 and posterior aspects of the second part of the duodenum where 

 the upper two- thirds and lower third of that part meet, there is a 

 small eminence of the mucous membrane, called the bile papilla. 

 It lies at the lower end of a vertically-placed valvula connivens, 

 which bifurcates so as to form a kind of cap for it. From the 

 lower part of the papilla a fold extends downwards for some distance, 

 which acts as a bridle, and gives the apex a downward direction. 

 On the summit of this papilla there is an opening which represents 

 the common orifice of the two ducts. These ducts, having traversed 

 the wall of the second part of the duodenum obliquely for | inch, 

 unite to form one duct which, before piercing the mucous coat, 

 presents an enlargement called the ampulla of Vater, but subse- 

 quently narrows at its final ending. In the ampulla of Vater 

 a gallstone may become lodged and delayed in its dovvTiward 

 progress toward the duodenum. About i inch above the bile papilla 

 there is another small papilla upon which there is another minute 

 opening. This represents the orifice of the accessory pancreatic 

 duct, or duct of Santorini. 



The villi commence at the beginning of the duodenum on 

 the outer side of the pylorus, and extend as far as the margins 

 of the segments of the ileo-cgecal valve. They are minute projec- 

 tions of the mucous mem- 

 brane, to which they impart 

 a woolly appearance, and may 

 be visible to the naked eye, 

 but are more readily seen 

 with the aid of an ordinary 

 lens if a portion of bowel is 

 floated in water. They are 

 closely set upon the mucous 

 membrane (vahnilae conni- 

 ventes included), except over 

 the solitary glands. Their 

 total number is said to be 

 about four millions (Krause). 

 The villi are conical, cylindri- 

 cal, leaf-like or finger-like pro- 

 cesses, varying in length from 

 aV to To inch. They are larger 

 and more numerous in the 

 lower part of the duodenum 

 and in the jejunum, especially 

 at its upper part, than in the 

 ileum, and they diminish both 



in size and mmiber from above downwards, becoming somewhat 

 filiform in the ileum. Each villus is an elevation of the mucous 

 membrane covered by a single layer of columnar epithelium. It 

 is composed of (i) adenoid tissue, (2) a capillary network of 



Fig. 338. — Two Villi. 



A. Villus, showing Striated Basilar 

 Border, Columnar Epithelium, Goblet 

 Cells, and Lacteal Vessel. B. Villus, 

 showing the Capillary Bloodvessels. 



