THE STOMACH 



1275 



Structure. The wall of the stomach consists of four coats serous, muscular, submucous, 

 and mucous, together with vessels and nerves. 



The serous coat (tunica serosa) is derived from the peritoneum, and covers the entire surface 

 of the organ, excepting along the greater and lesser curvatures, at ,the points of attachment of 

 the greater and lesser omenta; here the two layers of peritoneum leave a small triangular space 

 uncovered by peritoneum along which the nutrient vessels and 

 nerves pass. On the posterior surface of the stomach, close to the 

 cardiac orifice, there is also a small trianglar area uncovered by 

 peritoneum, where the organ is in contact with the under surface 

 of the Diaphragm. 



The muscular coat (tunica muscularis} (Figs. 998 and 999) is 

 situated immediately beneath the serous covering, to which it is 

 closely connected. It consists of three sets of smooth muscle tissue 

 : longitudinal, circular, and oblique, from without inward, in the 

 order named. 



The longitudinal fibres (stratum longitudinale} are the most 

 superficial, and are arranged in two sets. The first set consists of 

 fibres continuous with the longitudinal fibres of the oesophagus; 

 they radiate in a stellate manner from the cardiac orifice and are 

 practically all lost before the pyloric portion is reached. The 

 second set commences on the body of the stomach and passes to 

 the right, its fibres becoming more closely collected as they approach the pylorus. Some of 

 the more superficial fibres of this set pass on to the duodenum, but the deeper fibres dip in and 

 interlace with the circular fibres of the pyloric valve Sphincter. The bundles of longitudinal 



FIG. 997. Diagrammatic 

 view of the coats of the stom- 

 ach, duodenum, and . pylorus. 

 The ridge is the pyloric valve. 

 (Allan Thomson.) 



FIG. 998. The superficial muscular layer of the stomach, viewed from above and in front. (Spalteholz.) 



muscle fibre on the upper and lower surfaces of the pylorus are particularly firm and distinct, 

 and are called the pyloric ligaments (liyamenta pylori). 



The circular fibres (stratum circulare] form a uniform layer throughout the whole extent of 

 the stomach internal to the longitudinal fibres. They begin as tiny rings at the left extremity of 



