278 THE DIGESTIVE SYSTEM 



the larger blood and lymphatic vessels and nerve trunks which 

 supply the organ. 



THE MUSCULAR COAT of the stomach consists in general 

 of two layers of smooth muscle fibres a thin outer longitudinal, 

 and a much thicker inner circular and oblique layer. The regular 

 circular arrangement of these fibres is much distorted by the pe- 

 culiar dilatation and partial rotation to which the stomach is sub- 

 jected in the course of its development, and as a result of this 

 change obliquely placed fibres form a considerable portion of the 

 muscular coat. 



The oblique fibres are most numerous toward the cardiac end 

 of the stomach, where they form a third muscular layer, the inner- 

 most portion of the muscular coat. The longitudinal fibres are 

 most abundant toward the cardiac and pyloric orifices and along 

 the lesser curvature ; in the fundus and mid-region of the stomach 

 they form only a very thin layer. The circular fibres form the 

 thickest of the three muscular layers and are nearly equally dis- 

 tributed in all portions, except that at the cardiac and pyloric ori- 

 fices they become much thickened to form the sphincter muscles. 

 The pyloric sphincter is especially well developed (Fig. 229). 



The layers of the muscular coat of the stomach are united by 

 thin septa of connective tissue ; that between the longitudinal and 

 circular layers contains the nerve plexus of Auerbach and the 

 larger blood vessels which supply this coat. 



THE SUBMUCOSA consists of loose areolar tissue which sup- 

 ports the blood vessels, lymphatics, and the nerve plexus of Meiss- 

 ner, all of which distribute their branches to the mucous membrane. 

 In no portion of the stomach does this coat contain secreting glands. 



THE MUCOUS COAT. The muscularis mucosae forms a thin 

 but complete layer from one end of the stomach to the other, and 

 marks the outer boundary of the mucous membrane. It usually 

 consists of two thin layers, an inner circular and an outer longi- 

 tudinal. Here and there muscle fibres extend from the muscularis 

 mucosae into the corium between the gastric glands. 



The surface of the mucosa is clothed with tall columnar epi- 

 thelium, and the whole membrane is thrown into wavy folds, an 

 arrangement which is permitted by the very loose meshes of the 

 submucous areolar coat. The corium of the mucosa is closely 

 packed with tubular secreting glands, which open on the surface 

 by wide-mouthed, crypt-like ducts or f oveolae, and are embedded in 

 a fine fibro-reticular tissue containing many lymphatic corpuscles. 



