064 THE VASCULAR SYSTEMS 



gastric is doubly tied about one inch below the cardiac orifice at a point where it joins the lesse 

 curvature and is divided between the ligatures. The superior pyloric is doubly tied and divided 

 The fingers are passed beneath the pylorus, raising the gastrocolic omentum from the trans 

 verse mesocolon, and in this way safe ligation behind the pylorus of the right gastroepiploi 

 artery, or in most cases its parent vessel, the gastroduodenal, is secured. The left gastro 

 epiploic is now tied at an appropriate point, and the necessary amount of gastrocolic omentuc 

 doubly tied and cut." 1 Embolism of branches of the splenic artery is not uncommon in hear 

 disease, the embolus coming from the left side of the heart. It is characterized bv the occur 

 rence of a sudden sharp pain or "stitch" in the splenic region, with subsequent local enlarge 

 ment of the spleen from the formation of an infarct in its substance. 



The superior mesenteric artery (a. mesenterica 'superior) (Figs. 467 and 471 

 is a vessel of large size which supplies the whole length of the small intestine 

 except the first part of the duodenum: it also supplies the cecum and the ascendin; 

 and transverse parts of the colon. It arises from the front of the aorta about hal 

 an inch below the coeliac axis, and is covered at its origin by the splenic vein an< 

 the neck of the pancreas. It passes downward and forward in front of the lowe 

 part of the head of the pancreas processus uncinatus and the third portion o 

 the duodenum, and descends between the layers of the mesentery to the righ 

 iliac fossa, where, considerably diminished in size, it anastomoses with one of it 

 own branches viz., the ileocolic. In its course it forms an arch, the convexity o 

 which is directed forward and downward to the left side, the concavity backwar< 

 and upward to the right. It is accompanied by the superior mesenteric vein, an< 

 is surrounded by the superior mesenteric plexus of nerves. 



Dissection. In order to expose the superior mesenteric artery raise the great omentum an 

 transverse colon, draw down the small intestines, and cut through the peritoneum where th 

 transverse mesocolon and mesentery join; the artery will then be exposed just as it issues fror 

 over the unciform process of the head of the pancreas. 



Branches. Its branches are: 



Inferior pancreatScoduodenal. Ileocolic. 



Vasa intestini tenuis. Right colic. 



Middle colic. 



The inferior pancreaticoduodenal (a. pancreaticoduodenalis inferior) is given ol 

 from the superior mesenteric, or from its first intestinal branch behind the pan 

 creas. It courses to the right between the head of the pancreas and duodenum 

 and then ascends to anastomose with the superior pancreaticoduodenal artery 

 It distributes branches to the head of the pancreas and to the second and thir< 

 portions of the duodenum. 



The vasa intestini tenuis (aa. intestinales) arise from the convex side of tin 

 superior mesenteric artery. They are usually from twelve to fifteen in number 

 and are distributed to the jejunum (aa. jejunales) and ileum (aa. ileae). The; 

 run parallel with one another between the layers of the mesentery, each vesse 

 dividing into two branches, which unite with similar branches on each side 

 forming a series of arches the convexities of which are directed toward the intes 

 tine. From this first set of arches branches arise, which again unite with simila 

 branches from either side, and thus a second series of arches is formed; and fron 

 these latter, a third and a fourth, or even a fifth, series of arches is constituted 

 diminishing in size the nearer they approach the intestine. From the termina 

 arches numerous small straight vessels arise which encircle^ the intestine, upoi 

 which they are distributed, ramifying between its coats/ Throughout tliei 

 course small branches are given off to the nodes and other structures betweei 



1 William .1. Mayo, Annals of Surgery, March, 1904. 



