1152 



DIGESTIVE SYSTEM 



succeeded by a short constricted pyloric canal (Jonnesco) . At the lower end of this 

 canal the pylorus forms the aperture leading into the duodenum, and contains a 

 thick sphincter derived from the circular fibres of the muscular layer. The stom- 

 ach has two borders and two surfaces. The medial (or upper) border forms the 

 lesser curvature [curvatura ventriculi minor], which is concave (except near the 

 p^dorus) and gives attachment to the lesser omentum. The lateral (or lower) 

 border forms the greater curvature [curvatura ventriculi major], which is convex, 

 and gives attachment to the great omentum. The curvatures separate the 

 anterior surface [paries anterior], which faces forward and upward, from the 

 posterior surface [paries posterior], which is placed backward and downward. 



Dimensions. — The dimensions of the stomach are subject to great variation 

 and therefore only a gross approximation can be given. The length of the lesser 

 curvature averages about 10 cm. (7.5 cm. to 15 cm.), and that of the greater 



Fig. 907. — Longitudinal Section op Stomach, Showing the Interior of the Posterior 



Half. (Rauber-Kopsch. 



Fundus of stomach 



(Esophagus (pars abdominalis) 



Cardia 



Tela submucosa 



Sphincter py!"'-!^ 

 Pyloric valve 



Duodenum 

 (pars superior) 



Tunica serosa 

 Plicae mucosae 



Greater 

 curvature 



Pars pylorica 



curvature is three or four times as great. The diameter varies exceedingly accord- 

 ing to the amount of contents. When nearly empty, it presents, especially in 

 the pyloric portion, a narrow tubular form, with a diameter of about 4 cm. or 5 

 cm. (fig. 1108, Section XIII). The diameter of the pylorus, which is the narrow- 

 est point in the alimentary canal when constricted is only about 1.5 cm. It is 

 distensible, however, as hard bodies with diameters of 2 cm. or more may readily 

 pass through. _ , ^^.^ -j, p.\,j 



The average capacity of the stomach is between on6 and two litires, being sub- 

 ject to extreme individual variations. In the newborn, it averages about 30 cc. 

 (25 to 35 cc), increasing very rapidly in the early postnatal months and reaching 

 an average of 270 cc. at one year (liisscnko). The average weight of the adult 

 stomach is about 135 gm. 



Position and relations of the stomach. — The position and relations of the stom- 

 ach, like its form and structure, are subject to many variations in different indi- 



