1174 



THE DIGESTIVE SYSTEM. 



STRUCTURE OF THE STOMACH. 



The stomach wall is composed of four coats namely, from without inwards: (1) 

 Tunica serosa, (2) tunica muscularis, (3) tela submucosa, and (4) tunica mucosa (Fig. 924). 



Tunica Serosa. The serous coat is formed of the peritoneum, the relations of which 



to the stomach have already been described. It is 

 closely attached to the subjacent muscular coat, 

 except near the curvatures, where the connexion 

 is more lax; and it confers on the stomach its 

 smooth and glistening appearance. 



Tunica Muscularis. The muscular coat, which 

 is composed of unstriped muscle, is thinnest in the 

 fundus and body, much thicker in the pyloric 

 portion, and very highly developed at the pylorus. 

 It is made up of three incomplete layers an 

 external, stratum longitudinale ; a middle, stratum 

 circulare ; and an internal of oblique muscular fibres, 

 fibrce obliquce. 



The stratum longitudinale consists of longitu- 

 dinal fibres, continuous with those of the oesophagus 

 on the one hand, and those of the duodenum on 

 the other (Fig. 926, A). They are most easily 

 demonstrated on the lesser curvature, where they 

 can be traced down from the right side of the 

 oesophagus. Over the greater curvature and on the 

 two surfaces they are present as an extremely thin 

 and irregular sheet. Towards the pylorus the longi- 

 tudinal fibres grow much thicker, and, also much 

 tougher and more closely united, and they take part 

 in the formation of the pyloric valve. 



A specially condensed band of these can be often 



Stratum 

 longitudinale 



Tunica serosa 



FIG. 924. TRANSVERSE SECTION THROUGH 

 THE WALL OF A HUMAN STOMACH, x 250. 



made out both on the front and back at the antrum pyloricum, the form of which is said to 

 due to their presence. These bands are known as the ligamenta pylori (pyloric ligaments). 



Pyloric 

 N opening 



Pyloric canal 

 Icus intermedius 



--' Pyloric antrum 



FIG. 925. MUSCULAR COAT OF THE STOMACH, seen from within after removal of the mucous and submucous 

 layers. The anterior half of the stomach is shown, viewed from behind (Cunningham). 



The stratum circulare is composed mainly of circular fibres, continuous with the more 

 superficial of the circular fibres at the lower end of the oesophagus (Fig. 925). They 

 begin as a set of U-shaped bundles which loop over the lesser curvature at the right of 



