ABDOMINAL CAVITY 509 



pyloric constriction and examine the pyloric orifice and the pyloric canal. 

 Then remove a segment of the wall of the first part of the duodenum, 

 and dissect it to display its structure. 



Pyloric Orifice and Pyloric Canal. The extremity of the 

 pyloric canal protrudes into the commencement of the 

 duodenum, so that, when viewed from the duodenal side, it 

 presents the appearance of a smooth, rounded knob, sur- 

 rounded by a shallow furrow or fornix, and having a small 

 puckered orifice, the pyloric opening, in its centre. The 

 resemblance which it presents to the os uteri externum is very 

 striking. When the stomach has been properly hardened in 

 situ the pyloric orifice is almost invariably found tightly closed. 

 It is only on rare occasions that the opening is patent. In 

 such cases it is circular, and surrounded by a ring-like ledge 



Orifice of pyloric canal of stomach 



Termination of pyloric canal 

 protruding into duodenum 



Pvloric part of stomach 

 Duodenum- 



FIG. 195. Small portion of the Pyloric part of the Stomach with part 

 of Duodenum attached. 



which has been called the pyloric valve ; but it is doubtful if 

 this is a natural condition. During life the pyloric opening 

 may be regarded as being always rigidly closed, except during 

 digestion when it opens intermittently, and at irregular, 

 intervals, to allow material to be squirted from the stomach 

 into the duodenum. 



The muscular coat of the pyloric canal is modified to suit 

 the requirements of this section of the stomach. It is provided 

 with a powerful sphincteric apparatus. Both the circular and 

 longitudinal muscular fibres are present in greater mass than 

 in any other part of the organ. The circular fibres are 

 disposed in the form of a thick sphincteric muscular cylinder 

 which surrounds the entire length of the pyloric canal. At 

 the duodeno-pyloric constriction the margin of this cylinder 

 becomes increased in thickness, forming thereby the massive 

 muscular ring which encircles the pyloric orifice and con- 



