476 ABDOMEN 



As the peritoneum of the right side of the mesentery is removed take 

 away the fat lying between the two layers and clean the structures exposed. 

 They will be the (i) trunk of the superior mesenteric artery lying along the 

 root of the mesentery ; (2) the accompanying vein, which usually lies to the 

 right of the artery ; (3) the intestinal branches of the superior mesenteric 

 artery, passing forwards to the wall of the gut ; (4) the accompanying 

 veins and lymph vessels and nerves ; and (5) scattered at varying intervals 

 from the border of the gut to the superior mesenteric trunk in the root of the 

 mesentery, the mesenteric lymph glands which lie in the intervals between 

 the blood vessels. 



After the peritoneum has been removed from the posterior part of the 

 abdomen, between the root of the mesentery and the ascending colon, and 

 the extra-peritoneal fat has been cleaned away, a large number of structures 

 will be exposed. Most superficially, immediately behind the peritoneum, 

 will be found the right colic and ileo-colic branches of the superior 

 mesenteric artery with the accompanying veins, nerves, lymph vessels and 

 glands. In the upper part of the region, directly below the root of the 

 transverse meso-colon, the lower part of the second portion and the right 

 part of the third portion ot the duodenum will be found, with the superior 

 mesenteric artery and vein crossing in front of the latter and a small 

 part of the head of the pancreas in the angle between them. Behind the 

 superior mesenteric artery is a part of the aorta, and to the right of the 

 aorta the inferior vena cava. Partly behind the duodenum and partly 

 to the right ot" it, on a posterior plane, is the lower pole of the right 

 kidney. The right ureter emerges from behind the duodenum and 

 passes downwards along the medial border of the lower pole of the 

 kidney, and then behind the ileo-colic and the superior mesenteric arteries 

 on its way to the brim of the pelvis. The internal spermatic vessels 

 cross in front of the ureter (Fig. 184) and the genito-femoral nerve passes 

 downwards and laterally, behind the ureter, on the anterior surface 

 of the psoas magnus muscle. Beyond the lateral border of the psoas 

 magnus the fascia on the anterior surface of the quadratus lumborum will 

 be exposed. 



As the lower layer of the transverse meso-colon is removed the trunk 

 and branches of the middle colic artery and their anastomoses with branches 

 of the right and left colic arteries will be exposed, with the accompanying 

 veins, nerves, lymph vessels, and glands. 



When all the above-mentioned structures have been secured and 

 cleaned, the dissector should throw the small intestine over to the right 

 side and should then strip the peritoneum from the posterior wall of the 

 abdomen between the root of the mesentery to the right, and the descend- 

 ing and the iliac colon to the left. He should also remove the lower layer 

 of the left part of the transverse meso-colon. As he clears away the extra- 

 peritoneal fat, after the removal of the peritoneum, he will bring into view a 

 larger number of structures than on the right side. In the median plane, 

 below the root of the mesentery, lies the lower part of the abdominal 

 portion of the aorta, dividing, opposite the fourth lumbar vertebra, into the 

 two common iliac arteries, each of which is continued downwards into the 

 corresponding external iliac artery. On the surface of the aorta is the 

 aortic plexus of nerves which must be carefully preserved. To the right 

 of the aorta is the lower part of the inferior vena cava, and to the right of 

 and below the left common iliac artery is the left common iliac vein. 

 Springing from the front of the aorta, about one and a half inches above 

 its bifurcation and to the left of the median plane, is the inferior mesenteric 

 artery. The inferior mesenteric artery runs downwards on the left of the 



