BRANCHES OF THE ABDOMINAL AORTA 



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fi XI 



II. The anterior or great mesenteric artery 



(A. mesenterica cranialis) arises from the ventral 

 face of the aorta at the first lumbar vertebra. It 

 is a large unpaired trunk, about an inch (ca. 2-3 

 cm.) in length, which passes ventrally between the 

 vena cava and the left adrenal into the root of 

 the great mesentery, when it divides into three 

 branches— left, right, and anterior. ^ 



1. The left branch gives off at once about 

 fifteen to twenty arteries of the small intestine 

 (Aa. intestinales).^ These come off close together 

 and pass in divergent fashion l^etween the layers 

 of the great mesentery, each dividing into two 

 branches which anastomose with adjacent branches 

 to form a series of arches. In the anterior part of 

 the series secondary arches are formed by the union • 

 of branches given off from the primary set of 

 arches. From the convex side of these arches 

 terminal branches pass to the wall of the small 

 intestine, in which they ramify and form a vascu- 

 lar network. They are accompanied by satellite 

 veins and by nerves and lymph vessels. The first 

 artery anastomoses with the pancreatico-duodenal, 

 and the last with the ileal branch of the great 

 mesenteric artery. Branches are supplied to the 

 mesenteric lymph glands. 



2. The right branch (A. ileo-c£eco-colica) 

 might be regarded as the continuation of the 

 trunk. It runs downward and a little forward 

 and to the right, and gives off the ileal, the two 

 csecal, and the ventral colic arteries. (1) The 

 ileal or ileo-csecal artery (A. ilea) passes in retro- 

 grade fashion along the terminal part of the ileum 

 and unites with the last branch of the 'left division. 

 (2) The lateral caecal artery (Ramus csecalis later- 

 alis) passes between the caecum and the origin of 

 the colon and runs on the lateral band of the caecum 

 to the apex, where it anastomoses with the medial 

 artery. Besides numerous collaterals to the caecum, 

 it gives off the artery of the arch, which passes 

 along the lesser curvature of the base of the caecum 

 and runs on the lateral face of the origin of the 

 great colon. (3) The medial caecal artery (Ramus 

 caecalis medialis) passes along the medial band to 

 the apex of the caecum, where it anastomoses with 

 the lateral caecal artery. (4) The ventral colic 



' In the great majority of subjects this vessel and some 

 of its branches are the seat of more or less extensive vermin- 

 ous aneurysm, produced by the Solerostomum bidentatum. 

 In the author's experience an entirely normal specimen is 

 quite unlikely to be encountered except in very young foals. 



^ The left branch is a descriptive convention rather 

 than a reality, since the arteries of the small intestine spring 

 from the mesenteric trunk either directly or by short com- 

 mon stems with an adjacent vessel. 



