142 TOPOGRAPHIC AND APPLIED ANATOMY. 



psoas muscle. During its course the ureter describes a number of slight but typical curves. 

 The descending portion of the duodenum lies upon the right ureter while the duodenojejunal 

 flexure is superimposed upon the left one. The pelvic portion of the ureter is described upon 

 pages 149 and 151. 



The Abdominal Aorta. The abdominal aorta lies directly upon the vertebral column 

 and divides at the fourth lumbar vertebra into the two common iliac arteries. In thin individuals, 

 when the intestines are empty, the pulsations of the abdominal aorta may be palpated through 

 the belly wall, particularly if lordosis is present, as this approximates the vertebral column to the 

 anterior wall of the abdomen. The pulsations of the aorta may also be made palpable by tumors 

 situated behind the vessel and pushing it forward. The body of the pancreas crosses trans- 

 versely in front of the aorta at the level of second lumbar vertebra; the descending portion 

 of the duodenum passes across the vessel at a lower level. Below this situation the aorta is 

 covered only by peritoneum and may be easily exposed. Dilatations of the abdominal aorta 

 (aneurysms) produce pressure symptoms from the neighboring organs from the intestines, 

 from the liver, from the biliary passages, from the kidneys, and from the ureter (hydroneph- 

 rosis). 



The common iliac artery extends to the sacroiliac articulation and lies to the inner side of 

 the psoas muscle. It is behind the peritoneum and, upon both sides, is situated in front of and 

 somewhat to the left of the corresponding common iliac vein. It must occasionally be ligated, 

 and this may be accomplished without injury to the peritoneum. An incision is made two centi- 

 meters above and parallel to Poupart's ligament (Fig. 81) through the skin, the superficial fascia, 

 the abdominal muscles, and the transversalis fascia, exposing the peritoneum, which is pushed 

 away from the iliac fossa as the operator follows the course of the iliac vessels upward behind 

 the peritoneum. The external iliac artery is reached first (Fig. 81), and then follows the common 

 iliac; in the latter situation care must be taken to avoid the ureter, which runs in front of the 

 vessel. The incision must not be extended too far inward, as the inferior (deep) epigastric artery 

 would then be endangered (see page 121). 



The Inferior Vena Cava. The inferior vena cava lies upon the right side of the abdom- 

 inal aorta (Figs. 61 and 69), behind the ascending portion of the duodenum and the head of the 

 pancreas. Before its passage through the foramen venae cavae of the diaphragm it is imbedded 

 in the posterior margin of the liver (Fig. 49). For a description of the branches of the inferior 

 vena cava the reader is referred to the text-books upon systematic anatomy. 



REVIEW QUESTIONS. 



What arterial anastomosis in the anterior abdominal wall may become the chief collateral route 

 after an obstruction to the circulation in the descending aorta ? 



How would you draw a line upon the external surface of the abdomen to represent the course of the 

 inferior epigastric artery ? 



How would you explain a dilatation of the veins of the anterior abdominal wall following upon a 

 stasis in the region drained by the inferior vena cava? 



What are the effects of congestion of the portal system in diseases of the liver ? (In the anal, gas- 

 tric, and umbilical regions.) 



