The; Abdominal Aorta, etc. 133 



VII. THE ABDOMINAL AORTA, INFERIOR CAVAL VEIN, AND 

 SYMPATHETIC TRUNKS. 



The dissection and removal of the intestines and urinogenital organs 

 clears the dorsal body-wall for an examination of the abdominal 

 portion of the aorta, the inferior caval vein, and the sympathetic 

 trunks. If the inferior cava does not contain blood its tributaries should 

 be cleared first, in order to keep them from being damaged ; otherwise 

 the branches of the aorta should first be traced. The anterior portion of 

 the inferior cava has been removed with the liver. 



1. The abdominal portion of the aorta, described as the abdominal 

 aorta (aorta abdominalis), extends from the hiatus aorticus of the 

 diaphragm to the seventh lumbar vertebra, where it is replaced by the 

 paired common iliac arteries. It passes backward in a median position 

 along the ventral surfaces of the bodies of the vertebrae. Its natural 

 continuation backwards on the sacrum and the caudal vertebrae is 

 represented by the greatly reduced median sacral artery. 



The branches of the vessel are distributed in two series: (1) visceral 

 branches (rami viscerales) to the parts of the digestive tube and the 

 urinogenital organs; and (2) parietal branches (rami parietales) to the 

 body-wall. 



The visceral branches comprise the paired renal and spermatic 

 arteries, and the unpaired coeliac, superior mesenteric and inferior 

 mesenteric arteries, which have already been traced. 



The parietal brar^ches comprise : 



(a) The superior phrenic arteries (aa. phrenicae superiores), small 

 vessels arising in the hiatus aorticus and passing to the 

 diaphragm. 



(b) The twelfth intercostal artery (a. intercostalis xii), arising 

 on either side from the renal artery, and passing laterad to 

 the body wall. 



(c) The lumbar arteries (aa. lumbales), seven pairs of vessels 

 distributed metamerically to the lumbar portion of the 

 body-wall. Six pairs arise from the dorsal w^all of the aorta, 

 the seventh from the median sacral artery (d),each through 

 a common trunk. 



(d) The median sacral artery (a. sacralis media) arises from the 

 dorsal wall of the aorta near its posterior end, and passes 

 backward on the ventral surface of the sacrum. Its first 

 portion is concealed from the ventral surface by the common 

 hypogastric vein. 



2. The common iliac artery (a. iliaca communis) is a short trunk, the 

 branches of which pass to the posterior limb, the wall of the pelvis, and 

 the pelvic viscera. It gives off the iliolumbar artery (a. iliolumbalis), 

 which passes laterad to the body- wall, and then divides into two branches 

 the connections of which may be traced as follows: 



11 



