ABDOMINAL CAVITY 389 



superior epigastric artery descends in the interval between the 

 sternal and costal attachments of the diaphragm ; and the 

 musculo-phrenic artery passes between two slips of the costal 

 attachment opposite the eighth or ninth rib. 



VESSELS ON THE POSTERIOR WALL OF THE ABDOMEN. 



Dissection. The abdominal part of the aorta and its branches 

 and the inferior vena cava must now be cleaned. As the dis- 

 section proceeds the dissector must take care to secure the 

 gangliated trunks of the sympathetic, which extend downwards, 

 on the vertebral column, along the anterior borders of the psoas 

 major muscles. It is necessary to bear in mind that the lumbar 

 branches of the aorta, as they proceed laterally, pass behind the 

 sympathetic trunks. Separate the right crus of the diaphragm 

 from the aorta, and dissect in the interval between them. There 

 the cisterna chyli and the vena azygos will be found. A chain 

 of lymph glands, termed the lumbar glands, will be noticed in 

 relation to the aorta. The only branches of the aorta which 

 are liable to injury are the internal spermatic arteries. They 

 are two slender arteries which spring from the front of the 

 aorta, a short distance below the renal arteries. They are so 

 small that they are apt to be overlooked. 



Aorta Descendens, pars Abdominalis. The abdominal 

 part of the aorta is the direct continuation of the thoracic 

 part. It begins in the median plane, in the upper part of 

 the aortic orifice of the diaphragm, in front of the lower 

 border of the last thoracic vertebra ; and it ends in front of 

 the lower part of the body of the fourth lumbar vertebra, a 

 little to the left of the median plane, by dividing into the two 

 common iliac arteries. It therefore pursues an oblique course 

 inclining slightly to the left as it proceeds downwards. A line 

 drawn between the highest points of the iliac crests would 

 indicate the level of the bifurcation of the abdominal aorta, 

 which takes place a little below and to the left of the 

 umbilicus. 



Most of the structures which lie in front of the abdominal 

 aorta have been removed. In immediate relation to it from 

 above downwards are : ( i ) The coeliac plexus and the layer 

 of peritoneum which forms the posterior wall of the omental 

 bursa. (2) The pancreas and splenic vein. (3) The left 

 renal vein and the third part of the duodenum. (4) The 

 root of the mesentery and the superior mesenteric vessels. 

 (5) The peritoneum and the aortic plexus of nerves. More 

 n25 b 



