ABDOMINAL CAVITY 321 



different directions. Two, termed the anterior and posterior 

 ccecal arteries, pass respectively to the front and back of the 

 caecum ; one, a slender vessel, the artery to the vermiform process, 

 runs downwards behind the terminal part of the ileum and 

 supplies the vermiform process, which it reaches by passing 

 between the layers of the mesentery of that process ; a fourth, 

 the Heal artery, turns to the left along the ileum, it forms a 

 loop with the termination of the superior mesenteric trunk. 



Arteria Colica Dextra. The right colic artery arises 

 together with, or above, the ileo-colic, and passes to the right, 

 behind the parietal peritoneum on the posterior wall of the 

 abdomen. It divides into two branches, a superior and an 

 inferior. The superior branch ascends, and at the right colic 

 flexure it passes between the two layers of the transverse meso- 

 colon to inosculate with the middle colic ; whilst the inferior 

 branch joins the ascending branch of the ileo-colic artery. 

 From the convexity of the arches twigs proceed to the ascend- 

 ing colon, the right flexure of the colon, and part of the trans- 

 verse colon. 



Arteria Colica Media. The middle colic artery springs 

 from the upper part of the superior mesenteric. It passes, at 

 once, between the two layers of the transverse meso-colon, 

 and divides into a right and a left branch. The right branch 

 joins the superior part of the right colic, whilst the left branch 

 inosculates with the ascending part of the left colic artery, which 

 is derived from the inferior mesenteric. Arterial arcades are 

 thus formed in the transverse meso-colon, from which branches 

 proceed for the supply of the transverse colon. Some of the 

 branches pass beyond the transverse colon and descend 

 between the two posterior layers of the great omentum. 



Vena Mesenterica Superior. The superior mesenteric vein 

 is a large vessel which lies to the right of the superior 

 mesenteric artery. It receives tributaries from those parts of 

 the intestinal canal supplied by branches from the superior 

 mesenteric artery ; it also receives the right gastro-epiploic vein, 

 from the greater curvature of the stomach, and the pancreatico- 

 duodenal vein. It passes upwards, in front of the inferior part 

 of the duodenum, and, leaving the root of the mesentery, 

 disappears behind the neck of the pancreas, where it unites 

 with the splenic vein to form the vena porfce. 



Plexus Mesentericus Superior. The superior mesenteric 

 plexus is a dense plexus of sympathetic nerve twigs which 



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