STOMACH 



257 



Mucosa. 



Muscularis 



pression, are found in the pyloric glands of the dog. In certain respects 

 the pyloric glands are transitional between gastric and duodenal glands. 



The tunica propria consists of the small amount of reticular and connect- 

 ive tissue which is found between the closely packed glands and immedi- 

 ately beneath them (Fig. 249). 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 muscularis mucosae (Fig. 245). The lymphatic 

 vessels begin blindly 

 near the superficial epi- 

 thelium and pass be- 

 tween the glands into 

 the submucosa where 

 they spread out and 

 are easily seen; they 

 continue across the 

 muscularis and pass 

 through the mesentery 

 to join the large lym- 

 phatic trunks. Solitary 

 nodules occur in the 

 gastric mucosa, espe- 

 cially in the cardiac and 

 pyloric regions (Figs. 

 243 and 248) ; they may 

 extend through the 

 muscularis mucosae 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. Its elastic fibers are said to be abundant toward 

 the pylorus. 



The muscular coat of the stomach consists of three layers of smooth 

 muscle, an outer longitudinal, middle circular, and inner oblique layer 

 respectively. These layers can be recognized by dissection more readily 

 than by microscopic examination, and were found by Willis in 1674. 

 The middle layer is the one most highly developed. It not only sur- 

 rounds the body of the stomach, but as the fundus pushes outward, 

 muscle fibers of this layer encircle its apex concentrically. Toward the 

 pylorus, along the antrum, the circular layer gradually thickens, thus 

 forming the sphincter pylori; it becomes abruptly thin in the duodenum. 

 There is no sphincter at the cardia, where the circular layer is continuous 

 17 



Epithelium. 



Tunica propria. 



M uscularis mucosse. ^ 



Submucosa. 



Smooth muscle cut 

 lengthwise. 



Connective tissue. 



Smooth muscle cut 

 transversely. 



Serosa. 



FIG. 249. VERTICAL SECTION OF THE WALL OF A HUMAN STOMACH. 

 The tunica propria contains glands standing so close together that 



its tissue is visible only at the base of the glands toward the 



muscularis mucosae. 



