1166 



THE DIGESTIVE SYSTEM. 



The pylorus rests on the neck of the pancreas below and posteriorly, and is over- 

 lapped by the liver above and anteriorly. When the stomach is empty the pylorus 

 is usually placed near (i.e. within 1 inch, 12 mm. of) the median plane, below the left 

 lobe or sometimes the quadrate lobe of the liver, and at the level of the first lumbar 

 vertebra, or the fibre-car tilage between this and the second lumbar. During disten- 

 tion it is pushed over beneath the quadrate lobe for a variable distance, but very 

 rarely more than 1J or 2 inches to the right of the median plane. Its average 

 position can be marked on the surface of the body by the intersection of two lines ; 

 one drawn horizontally half-way between the top of the sternum and the pubic crest 

 (Addison), the other drawn vertically a little way (J inch, 12 mm.) to the rio-ht of 

 the median plane. 



During the earlier stages of gastric digestion the sphincter pylori is strongly contracted 

 and the aperture firmly closed, but it opens intermittently to allow of tlie passage of properly 

 digested portions of the food. As digestion advances the sphincter probably relaxes somewhat 

 but in hardened bodies a really patent pylorus is rarely or never found, which would seem to 



Pyloric sphincter 

 Longitudinal muscular coat 



Circular muscle 

 fibres of the duodenum 



Duodenal glands 



Longitudinal muscular coat 

 (duodenum) 



Mucous meinbraiK 

 of the duodenum 



Duodenum 



Pyloric canal ] 

 Longitudinal muscular coat | 



Mucous coat 



Pyloric sphincter 



Pyloric orifice 



Duodenal glands 



FIG. 917. LONGITUDINAL SECTION THROUGH THE PYLORIC CANAL AND COMMENCEMENT OF THE 

 DUODENUM IN A NEW-BORN CHILD. (From Stiles.) 



indicate that the pylorus is normally closed, or nearly so, and that its opening is an active rathei 

 than a passive condition, as in the case of the anal canal. 



As regards its size, the pylorus is stated to be about \ inch (12 - 5 mm.) in diameter, but then 

 is no doubt that this represents neither its full size nor its calibre when at rest. Foreigr 

 bodies with a diameter of f to 1 inch have been known to pass through the pylorus withou 

 giving rise to trouble, even in children. On the other hand, when at rest, with an empt? 

 stomach and duodenum, the aperture is practically closed. 



Curvatura Ventriculi Minor. The lesser curvature is directed towards tht 

 liver, and corresponds to the line along which a fold of peritoneum calle( 

 the hepa to- gastric ligament is attached to the stomach, between the pyloric am 

 cesophageal orifices (Fig. 916). The fold connects the stomach and liver, am 

 between its two layers the gastric vessels run along the curvature of the stomach. 



While the lesser curvature is, on the whole, concave, it consists of two portion 

 which meet and form a sharp angle, called the incisura angularis, situated neare 

 the pyloric than the cardiac end, though its position varies with the condition of tb 

 stomach. The superior or left portion is nearly vertical, and continues the directioi 

 of the right margin of the oesophagus, while the inferior or right portion is mor 

 nearly horizontal, when viewed from the front. The depth and acuteness of the angl 

 between these two segments varies with the degree of distension of the stomacl 

 When the pyloric portion of the stomach is full, the inferior portion of the lesse 



