THE DIGESTIVE SYSTEM 



257 



- d 



Lying near the basement membrane among the bases of the colum- 

 nar epithelial cells are small spherical or irregular cells with dark 

 nuclei. These are young epithelial cells which from their function 

 are known as "replacing cells" (see page 75). 



The PYLORIC GLANDS (Figs. 160 and 16 j) are simple branched 

 tubular glands, several of which open into each of the deep pyloric pits. 

 These pits occupy a much greater pro- 

 portion of the thickness of the mucous 

 membrane than do the ])its of the fun- 

 dus glands (compare Figs. 156 and 160) 

 and the proportionate depth occupied 

 by the glands themselves is correspond- 

 ingly less. The pyloric glands, though 

 short, are quite tortuous, so that in sec- 

 tions the tubules are seen cut mainly 

 transversely or obliquely. In most of 

 the pyloric glands but one type of cell 

 is found. These resemble the chief cells 

 of the fundus, but present a more uni- Fig. isg.-Longitudinal Section 



' J^ \ of fundus of Gland from rj-lonc 



form appearance, probablyMue to the End of Dog's Stomach. (Golgi 



, c • . 1 11 A • ^1 method. See <;, p. 20.) a, Lumen 



absence of parietal cells. As m the of gland; i, intracellular canals in 



fundus, "replacing cells" lie between parietal cells; c cut-off portion of 



. . parietal cell; a, chief cells; e, inter- 



the bases of the columnar epitheHal cellular canals leading from lumen 



cells. Parietal cells are not always en- °^ ^land to canals in parietal ceUs. 

 tirely absent, but occur here and there in the pyloric tubules, espe- 

 cially near the fundus. 



The transition from fundus to pylorus is not abrupt, but is 

 marked by a "transitional border zone," in which fundus and pyloric 

 glands are interiTiingled, and in which are also found single glands 

 which resemble in structure both fundus and pyloric. 



In the transition zone between oesophagus and stomach are found 

 glands which resemble those found in the lower end of the oesophagus 

 (p. 250). Their cells are clear resembling those of the pyloric glands. 

 On account of their location they have been designated cardiac glands. 

 Those nearest the cjesophagus are lined with clear cells and re- 

 semble closely the pyloric glands. As one passes further from the 

 oesophageal junction, cells with coarse granules begin to make their 

 appearance among the clear cells and, assuming the character of 

 parietal cells, become more and more numerous, the glands thus 

 passing over by gradual transition into typical fundus glands. There 



