3G8 



THE DIGESTIVE SYSTEM 



Villi are found upon the free surface of the agminate nodules only 

 in the intervals between the constituent units. The largest of the 

 nodules lie near the center of the patch, the smallest are found at its 

 periphery. The agminate nodules become the chief seats of infection in 

 typhoid fever. 



Above the level of the ileum the largest collections of lymphoid 

 tissue in the intestinal mucosa occur in the upper part of the duo- 

 denum, where there are extensive infiltrations of dense lymphoid tissue, 

 many of which contain typical nodules with germinal centers. These 



masses of lymphoid 

 tissue are pene- 

 trated by the ducts 

 of the duodenal 

 glands, whose se- 

 creting portions 

 form a bed upon 

 which the lymphoid 



Villus 



Lacteal 



Goblet cell 



'Intestinal gland 



Muscularis mucosae 



FIG. 343. DIAGRAM OF SMALL INTESTINE, SHOWING THE 

 TOPOGRAPHICAL RELATIONSHIP OF THE INTESTINAL 

 GLANDS (CRYPTS OF LIEBERKUHN) TO THE VILLI. 



tissue rests. The 

 duodenal patches 

 differ slightly from 

 those in the ileum 

 -in that they form a 



more confluent mass with relatively fewer nodules, possess a more diffuse 

 character, are more deeply situated, and are therefore covered by the 

 corium of the mucosa which contains both intestinal glands and villi. 



THE INTESTINAL VILLI. The intestinal villi are long finger- 

 like projections (from 0.5 to 1 millimeter in length) which vary 

 much in form in different mammals and in different portions of the 

 canal in the same individual. They are perhaps most highly developed 

 in the dog, where they form long projections with expanded or clubbed 

 extremities and a constricted base or neck. 



In man the villi are of a more conical shape, the base being, as a 

 rule, slightly broader than the free extremity. In the duodenum of 

 man they possess a foliate shape, in the jejunum they are conical or 

 somewhat clavate, in the ileum they are generally filiform. The villi 

 are most abundant in the duodenum and the jejunum (24 to 40 per 

 square millimeter) and less numerous in the ileum (15 to 30 per square 

 millimeter) (Piersol). According to Johnson (Amer. Jour. Anat., 14, 

 2, 1913) they are more or less variable structures, their shape and 

 height changing with the degree of distention of the tube. 





