1164 



SPLANCHNOLOGY 





The position of the full stomach depends, as already indicated, on the state of the intestines; 

 when these are empty the fundus expands vertically and also forward, the pylorus is displaced 

 toward the right and the whole organ assumes an oblique position, so that its surfaces are directed 

 more forward and backward. The lowest part of the stomach is at the pyloric vestibule, which 

 reaches to the region of the umbilicus. Where the intestines interfere with the downward 

 expansion of the fundus the stomach retains the horizontal position which is characteristic of 

 the contracted viscus. 



Examination of the stomach during life by x-rays has confirmed these findings, and has 

 demonstrated that, in the erect posture, the full stomach usually presents a hook-like appear- 

 ance, the long axis of the clinical fundus being directed downward, medialward, and forward 

 toward the umbilicus, while the pyloric portion curves upward to the duodenopyloric junction. 



Interior of the Stomach. When examined after death, the stomach is usually fixed at some 

 temporary stage of the digestive process. A common form is that shown in Fig. 1050. If the 

 viscus be laid open by a section through the plane of its two curvatures, it is seen to consist of 

 two segments: (a) a large globular portion on the left and (6) a narrow tubular part on the 

 right. These correspond to the clinical subdivisions of fundus and pyloric portions already 

 described, and are separated by a constriction which indents the body and greater curvature, 

 but does not involve the lesser curvature. To the left of the cardiac orifice is the incisura 

 cardiaca: the projection of this notch into the cavity of the stomach increases as the organ 

 distends, and has been supposed to act as a valve preventing regurgitation into the esophagus. 

 In the pyloric portion are seen: (a) the elevation corresponding to the incisura angularis, and 

 (6) the circular projection from the duodenopyloric constriction which forms the pyloric valve; 

 the separation of the pyloric antrum from the rest of the pyloric part is scarcely indicated. 



Antrum cardiacum 

 Pyloric valve 



Pylorus 

 Pyloric antrum 



FIG. 1050. Interior of the stomach. 



The pyloric valve (valvula pylori) is formed by a reduplication of the mucous 

 membrane of the stomach, covering a muscular ring composed of a thickened por- 

 tion of the circular layer of the muscular coat. Some of the deeper longitudinal 

 fibers turn in and interlace with the circular fibers of the valve. 



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

 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 area uncovered by peritoneum, where the organ 

 is in contact with the under surface of the diaphragm. 



The muscular coat (tunica muscularis) (Figs. 1051, 1052) is situated immediately beneath the 

 serous covering, with which it is closely connected. It consists of three sets of smooth muscle 

 fibers: longitudinal, circular and oblique. 



The longitudinal fibers (stratum longitudinale) are the most superficial, and are arranged in 



