286 THE DIGESTIVE SYSTEM 



From these arches, arteries lying in the subserous connective 

 tissue are distributed to the ventral and dorsal surfaces of the 

 gastric wall. These vessels supply branches which penetrate the 

 muscular coat, giving off, on the way, arterioles to the intramuscu- 

 lar septum, and secondarily to the intramuscular capillary plexus, 

 and spread out in the areolar tissue of the submucosa in which 

 they form an extensive arterial plexus. Branches from this sub- 

 mucous plexus enter the mucous membrane and form a dense 

 capillary plexus whose elongated meshes inclose the secreting 

 glands. 



Near the surface of the mucosa these vessels enter a plexus of 

 small venules which, by union, form larger branches and convey 

 the blood outward to a venous plexus at the outer border of the 

 mucosa, whence it returns to the larger veins of the submucosa. 

 These veins, after receiving venules from the muscular coat, pass 

 outward to the subserous connective tissue in company with the 

 entering arteries and finally reach the gastric, splenic, and portal 

 veins. 



THE LYMPHATICS arise by vascular loops or dilated extremi- 

 ties between the secreting glands of the mucosa. At the outer 

 border of the mucous membrane they form a delicate anastomosing 

 plexus from which branches penetrate the muscularis mucosae and 

 enter a broader submucous plexus whose efferent vessels pierce the 

 muscular coat on their way to lymphatic glands which are situated 

 in the folds of the omentum at either curvature of the stomach. 



THE NERVES of the stomach are derived from the sympa- 

 thetic and pneumogas tries. They enter with the blood vessels and 

 pierce the muscular coat to form two plexuses of anastomosing 

 nerve trunks ; the one ( Auerbach's) in the intramuscular fibrous 

 septum contains ganglionic enlargements at many of its intersec- 

 tions and distributes its fibrils to the smooth muscle ; the other 

 (Meissner's), lying in the deeper part of the submucosa also con- 

 tains small ganglia at the intersections of its anastomosing 

 branches. This latter plexus is much finer than that of the mus- 

 cular coat ; it distributes its fibrils to the mucosa, where they ter- 

 minate in and about the walls of the blood and lymphatic vessels 

 and beneath the epithelium of the secreting glands. 



SMALL INTESTINE 



The structure of the serous coat of the small intestine is iden- 

 tical with that of the stomach. The muscular coat consists of an 



