354 



HANDBOOK OF PHYSIOLOGY. 



THB STOMACH. 



In man and those Mammalia which are provided with a single stom- 

 ach, it consists of a dilatation of the alimentary canal placed between 

 and continuous with the oesophagus, 

 which enters its larger or cardiac 

 end on the one hand, and the small 

 intestine, which commences at its 

 narrowed end or pylorus, on the 

 other. It varies in shape and size 

 according to its state of distention. 



Structure. The stomach is com- 

 posed of four coats, called respec- 

 tively (1) an external or peritoneal, 

 (2) muscular, (3) submucous, and 

 (4) mucous coat; with blood-vessels, 

 lymphatics, and nerves distributed 

 in and between them. 



(1) The peritoneal coat has the 

 structure of serous membranes in 

 general, as has been described. (2) 

 The muscular coat consists of three 

 separate layers or sets of fibre, which, 

 according to their several directions, 

 are named the longitudinal, circular, 

 and oblique. The longitudinal set 

 are the most superficial: they are 

 continuous with the longitudinal 

 fibres of the oesophagus and spread 

 out in a diverging manner over the 

 cardiac end and sides of the stom- 

 ach. They extend as far as the py- 

 lorus, being especially distinct at 

 the lesser or upper curvature of the 

 stomach, along which they pass in 

 several strong bands. The next set 

 are the circular or transverse fibres, 

 which more or less completely en- 

 circle all parts of the stomach ; they 

 are most abundant at the middle and in the pyloric portion of the or- 

 gan, and form the chief part of the thick projecting ring of the pylorus. 

 These fibres are not simple circles, but form double or figure-of-8 loops, 

 the fibres intersecting very obliquely. The next, and consequently 



Fig. 249. From a vertical section through 

 the mucous membrane of the cardiac end of 

 stomach. Two peptic glands are shown with a 

 duct common to both, one gland only in part, 

 a, duct with columnar epithelium becoming 

 shorter as the cells are traced downward ; n, 

 neck of gland tubes, with central and parietal 

 or so-called peptic cells ; 6, f undus with curved 

 caecal extremity the parietal cells are not so 

 numerous here. X 400. (Klein and Noble 

 Smith.) 



