THE DIGESTIVE SYSTEM 



267 



'-'ii^. c 



its junction with the jejunum. Thc>- always occur on the side of 

 the gut opposite the attachment of the mesentery. Each patch 

 consists of from ten to seventy nodules, so arranged that the entire 

 patch has a generally oval shape, its long diameter lying lengthwise 

 of the intestine. The nodules of which a patch is composed he side 

 by side. Their apices are directed toward the lumen and project 

 almost through the mucosa, being uncovered by villi, a single layer 

 of columnar epithelium alone separating their surfaces from the 

 lumen of the gut. The bases of the nodules are not confined to the 

 stroma, but usually spread out in the submucosa. The relation of 

 the patch to the stroma and submucosa can be best appreciated by 

 following the course of the muscularis mucosae. This is seen to stop 

 abruptly at the circumference 

 of the patch, appearing through- 

 out the patch as isolated groups 

 of smooth muscle cells. The 

 nodules rarely remain distinct, 

 but are confluent with the ex- 

 ception of their apices and 

 bases. It should be noted that 

 both solitary nodules and 

 Peyer's patches are structures 

 of the mucosa, and that their 

 presence in the submucosa is 

 secondary. 



The muscularis mucosae 

 (Figs. 165 and 171) consists of 

 an inner circular and an outer 

 longitudinal layer of smooth 

 muscle. 



2. The submucosa (Figs. 

 163, 165, 171) consists, as in the 

 stomach, of loosely arranged 

 connective tissue and contains 

 the larger blood-vessels. It is 



' " ' "' '■•••■•■••••••••• -••••••■•••■—■-^•_^_ 



Fig. 171 . — From Vertical Longitudi nal Sec- 

 tion of Cat's Duodenum to show Brunner's 

 Glands. (Larrabee.) a, Villus; b, epithe- 

 lium; c, stroma; d, glands; e, muscularis 

 mucosas; /, Brunner's glands; g, submucosa; 



free .from glands except in the /'- circular muscle layer. 

 duodenum, where it contains the glands of Brunner (Fig. 171). 

 These are branched tubular glands hned with a granular columnar 

 epitheHum similar to that of the pyloric glands. The ducts are also 

 lined with simple columnar epithehnin. They pass through the 



