vii THE DIGESTIVE SYSTEM AND ITS FUNCTIONS 141 



cells and present a very different appearance from the cells 

 lining the mouth and neck. They are polygonal in outline, 

 with large round or oval nuclei and granular cytoplasm ; the 

 lumen or central cavity of the gland in this region is very 

 small and at times almost obliterated. The lower ends of 

 the glands extend as far as the muscularis mucosae. 



In the pyloric end of the stomach the glands are less deep. 

 The mouth of the gland, however, is relatively deeper than 

 in the cardiac end, but is lined by much the same kind of 

 cells. At the bottom of the gland there are several large 

 polygonal cells with very large clear vacuoles much like 

 the cells in the necks of the cardiac glands. Occasion- 

 ally there may be a few polygonal granular cells below 

 these. In general, however, the pyloric glands may be said 

 to correspond to the mouth and neck of the glands of 

 the cardiac end of the stomach. Like the latter, these 

 glands frequently branch, but the branching commonly takes 

 place above the body of the gland. 



The histological structure of the esophagus resembles in 

 a general way that of the stomach. There is an external 

 layer of longitudinal muscles and an inner layer of circular 

 fibers, but both are comparatively thin. A muscularis 

 mucosae is lacking except close to the stomach, where it is 

 represented by a few scattered fibers. The mucosa is well 

 developed ; the surface epithelium consists of cylindrical 

 mucous cells with ciliated cells scattered among them. 



The glands of the mucous layer are comparatively large 

 and much branched ; and in many cases the branches, which 

 may be as many as fifteen in number, redivide. Near the 

 mouth the glands are small in size, and toward the stomach 

 they become smaller again and more simple in structure. 

 The cells of the body of the esophageal glands have a 

 granular appearance much like the corresponding cells of 



