STOMACH. 203 



nucleus near its base, and protoplasm resembling that of chief cells. In 

 structure the pyloric glands are like the duodenal glands, but the latter 

 extend into the submucosa. 



The gastric glands are so closely packed that but little reticular and 

 connective tissue of the tunica propria is found between them (Fig. 227). 

 It is sufficient to support the numerous capillaries branching about the 

 glands, the terminal lymphatic vessels and nerves, numerous wandering 

 cells and a few vertical smooth muscle fibers prolonged from the muscu- 

 laris mucosae (Fig. 223). The lymphatic vessels begin blindly near the 

 superficial epithelium and pass between the glands into the submucosa 

 where they spread out and are easily seen; they continue across the mus- 

 cularis and pass through the mesentery to join the large lymphatic 

 trunks. Solitary nodules occur in the gastric mucosa, especially in the 

 cardiac and pyloric regions; they may extend through the muscularis mu- 

 cosae into the submucosa. The muscularis mucosae may be divided into 

 two or three layers of fibers having different directions. The submucosa 

 contains its plexus of nerves and many vessels, together with groups of fat 

 cells. 



The muscularis consists of a thick inner circular and a thin outer 

 longitudinal layer, together with oblique fibers sometimes described as a 

 third and innermost layer. Owing to the distention and twisting in the 

 development of the stomach the course of the fibers is disturbed, and in 

 small sections they may appear to run in every possible direction. The 

 two layers are clearly marked at the pylorus, where a great thickening of 

 circular fibers produces the sphincter muscle. Longitudinal fibers have 

 been said to be involved in it so that they can act as a dilator of the pylorus. 



The serosa consists of connective tissue with well developed elastic 

 nets, and of the peritoneal mesothelium interrupted only at the mesenteric 

 attachments. The serosa contains the vessels and nerves which supply 

 the stomach. The nerves are partly vagus branches (the left vagus sup- 

 plies the ventral surface and the right vagus the dorsal surface owing to the 

 rotation of the stomach during its development) and partly sympathetic 

 nerves from the cardiac plexus. The distribution of vessels and nerves is 

 similar to that in the intestine, which will be described in detail. 



SMALL INTESTINE DUODENUM. 



The mucous membrane of both the small and the large intestine con- 

 tains many simple tubular glands, which reach but do not penetrate the 

 muscularis mucosae. They are called intestinal glands [crypts of Lieber- 

 kiihn]. Besides these, but in the small intestine only, there are cylindrical, 

 club-shaped or foliate elevations of the epithelium and tunica propria, 



