DUODENUM 



259 



plexus. The further distribution of the nerves in myenteric and sub- 

 mucous plexuses is similar to that in the small intestine. 



DUODENUM. 



The duodenum contains branched mucous glands, the bodies of which 

 are found in the submucosa. These are called duodenal glands (B runner's 



Intestinal gland 

 Epithelium. Villi. 



Duodenal gland. 

 /'Plica, circularis. 



Fat. Duodenal glands in the 

 submucosa. 



Tunica propria 



Muscularis 



mucosas. ' 

 Submucosa. r 



Stratum of \ ' 



circular muscle. t-. 



Stratum of longi- g 

 tudinal muscle. ~. 



Connective tissue . 



Intestinal glands 



Longitudinal 

 section. 



FIG. 251. LONGITUDINAL SECTION OF THE HUMAN DUODENUM. X 16. 



glands) and they occur nowhere else in the small intestine (Fig. 251). 

 Their cells produce a mucus which stains with difficulty, thus contrasting 

 with the mucus of the goblet cells in the 

 tubular glands above them. The nature 

 of their epithelium is shown in Fig. 252, 

 which shows also that a portion of their 

 tubules may lie above the muscularis 

 mucosae, in the tunica propria. As in the 

 pyloric glands, occasional parietal cells 

 have been found, and also the dark cells, 

 due to compression. Secretory capillaries 

 extend out from the lumen between the 

 cells, and the tubules are provided with a 

 structureless basement membrane. The 

 ducts of the duodenal glands may open 

 on the free surface of the epithelium, or 

 into the lower ends of the tubular pits 

 situated in the mucous membrane and 

 known as intestinal glands. The duodenal 

 glands are so numerous toward the stom- 

 ach that the submucosa may be filled 

 with their tubules. They are also abun- 

 dant near the duodenal papilla where the 



Transverse 

 section. 



Longitudinal 

 section. 



of the tubules of a duodenal gland. 



FIG. 232. FROM A SECTION OF A HUMAN 



DUODENUM. X 240. 

 Only the lower half of the mucosa and 



upper half of the submucosa are 



sketched. 



