ABDOMINAL AORTA. 497 



branch, which supplies the vertebrae, the spinal cord and its membranes, and a 

 muscular branch, which is distributed to the muscles and integument of the back. 



THE ABDOMINAL AOETA. (Fig. 289.) 



The Abdominal Aorta commences at the aortic opening of the Diaphragm, in 

 front of the body of the last dorsal vertebra, and, descending a little to the left 

 side of the vertebral column, terminates on the left side of the body of the 

 fourth lumbar vertebra, where it divides into the two common iliac arteries. It 

 diminishes rapidly in size, in consequence of the many large branches which it 

 gives off. As it lies upon the bodies of the vertebras, the curve which it de- 

 scribes is convex forwards, the greatest convexity corresponding to the third 

 lumbar vertebra, which is a little above and to the left side of the umbilicus. 



Relatioiis, It is covered, in front, by the lesser omentum and stomach, behind 

 which are the branches of the cceliac axis, and the solar plexus; below these, by 

 the splenic vein, the pancreas, the left renal vein, the transverse portion of the 

 duodenum, the mesentery, and aortic plexus. Behind, it is separated from the 

 lumbar vertebrae by the left lumbar veins, the receptaculum chyli, and thoracic 

 duct. On the right side, it is in relation with the inferior vena cava (the right 

 crus of the Diaphragm being interposed above), the vena azygos, thoracic duct, 

 and right semilunar ganglion ; on the kft side, with the sympathetic nerve, and 

 left semilunar ganglion. 



PLAN OF THE EELATIONS OF THE ABDOMINAL AOKTA. 



Infront. 



Lesser omentum and stomach. 

 Branches of coaliac axis and solar plexus. 

 Splenic vein. 

 Pancreas. 

 Left renal vein. 

 Transverse duodenum. 

 Mesentery. 

 Aortic plexus. 



Right side. /^ "~\ Left side. 



Bight crus of Diaphragm. / \ Sympathetic nerve. 



Inferior vena cava. [ Abdominal | Left semilunar ganglion. 



Yena azygos. 

 Thoracic duct. 

 Eight semilunar ganglion. 



Behind. 



Left lumbar veins. 

 Receptaculum chyli. 

 Thoracic duct. 

 Vertebral column. 



Surgical Anatomy. Aneurisms of the abdominal aorta near the cceliac axis communicate in 

 nearly equal proportion with the anterior and posterior parts of the artery. 



When an aneurism al sac is connected with the back part of the abdominal aorta, it usually 

 produces absorption of the bodies of the vertebra?, and forms a pulsating tumor, that presents 

 itself in the left hypochondriac or epigastric regions, accompanied by symptoms of disturbance 

 of the alimentary canal. Pain is invariably present, and is usually of two kinds, a fixed and 

 constant pain in the back, caused by the tumor pressing on or displacing the branches of the 

 solar plexus and splanchnic nerves, and a sharp lancinating pain, radiating along those branches 

 of the lumbar nerves which are pressed on by the tumor ; hence the pain in the loins, the testes, 

 the hypogastrium, and in the lower limb (usually of the left side). This form of aneurism usually 

 bursts into the peritoneal cavity, or behind the peritoneum, in the left hypochondriac region ; or 

 it may form a large aneurismal sac, extending down as low as Poupart's ligament ; hemorrhage 

 in these cases being generally very extensive, but slowly produced, and not rapidly fatal. 



When an aneurismal sac is connected with the front of the aorta near the coeliac axis, it forms 

 a pulsating tumor in the left hypochondriac or epigastric regions, usually attended with symp- 

 toms of disturbance of the alimentary canal, as sickness, dyspepsia, or constipation, and accom- 

 panied by pain, which is constant, but nearly always fixed in the loins, epigastrium, or some 

 part of the abdomen ; the radiating pain being rare, as the lumbar nerves are seldom implicated. 

 32 



