3-50 



STRUCTURE OF THE STOMACH. 



phatics of the stomach pass within these duplicatures of the membrane, 

 and reach the organ along its two cnrvatnres. Its anterior and posterior 

 surfaces are free, smooth, and covered with peritoneum. The anterior 

 surface, which is directed upwards as well as forwards, is in contact 

 above with the diaphragm and the under surface of the liver, and lower 

 down with the abdominal parietes 0])posite the epigastric region, which 

 is hence named the pit of the stomach. The posterior surface is turned 

 downwards and backwards, and rests upon the transverse meso-colon, 

 behind which are the pancreas and great vessels of the abdomen. 



At its cardiac orifice it is continuous with the gullet, and is there 

 fixed by a reflection of peritoneum to the oesophageal opening in the 

 diaphragm. The pyloric extremity, situated lower down, nearer to 

 the surface, and having greater freedom of motion, is continuous with 

 the duodenum, is covered by the concave surface of the livei", and in 

 some cases touches tlie neck of the gall-bladder. _ 



When the stomach is distended, its position and direction are 

 changed. The great curvature is elevated and at the same time car- 

 ried forwards, whilst the anterior surface is turned upwards, and the 

 posterior surface downwards. 



STRUCTURE. 



The stomach has four coats, named, in order from without inwards, 

 the serous, muscular, areolar or submucous, and mucous coats (fig. 245). 

 Taking all the coats together, they are thinner than those of the oeso- 

 phagus, but rather thicker than those of the intestines generally. They 

 are thickest at the pyloric end, and thinnest in the great cul-de-sac. 



Fi£r. 245. 



Fig. 245. — Diagrammatic View in Perspective 

 OF A Portion op the Coats of the Stomach 

 AND Duodenum, including the Pylorus 

 (Allen Thomson). 



g, the inner surface of the gastric mucous 

 membrane ; g', section of the mucous membrane 

 with the pyloric gastric glands ; r, the villous sur- 

 face of the mucous membrane of the duodenum : 

 I, section of the same vnih the intestinal glands 

 ui- cryirts of Lieberkilhn; p p, the ridge of the 

 })yloric ring, with a section of its component 

 parts ; m i, deep or circular layer of muscular 

 fibres : these are seen in the section to form the 

 pyloric sjihincter ; m e, external or longitudinal 

 layer of muscular fibres ; s, the serous covering. 



The external or serous coat {s), derived from the peritoneum, is a 

 thin, smooth, transparent, and elastic membrane which closely covers 

 the entire viscus, excepting along its two curvatures. Along the line 

 of these curvatures the attachment is looser, leaving an interval occu- 

 pied by the larger blood-vessels. 



The second or musctQar coat, is composed of plain muscular tissue, 

 forming three sets of filjres, disposed in layers, and named, from their 

 direction, the longitudinal, the circular, and the oblique fibres. 



The first or outermost layer consists of the toiKjitudinal fibres (fig. 

 245, we, fig. 246, A), which are in direct continuity with those of the 

 oesophagus. They spread out in a radiating manner from the cardiac 

 orifice, and are found in greatest abundance along the curvatures, espe- 



