390 ABDOMEN 



superficially it is covered by the lesser omentum ; the liver ; 

 the stomach ; the transverse colon and its mesentery ; and by 

 the great omentum and the coils of the small intestine. Behind, 

 the abdominal aorta rests upon the bodies of the lumbar 

 vertebrae and the intervertebral nbro-cartilages, separated from 

 them, however, by the anterior longitudinal ligament and the 

 left lumbar veins. On each side, it is related, in its upper part, 

 to the crus of the diaphragm. On the right side, the inferior 

 vena cava lies close to the aorta, as high as the second 

 lumbar vertebra, but above that it is separated from the aorta 

 by the fleshy part of the right crus. In the interval between 

 the right crus of the diaphragm and the aorta, the dissector has 

 already noted the cisterna chyli and the vena azygos. On 

 each side, the gangliated trunk of the sympathetic is in 

 relation to the artery, below the level of the crura of the 

 diaphragm. 



Branches of the Abdominal Aorta. The branches of the 

 abdominal aorta may be described under two heads, viz. 

 (i) Those which come off in pairs. (2) Those which 

 arise singly. 



PAIRED BRANCHES. 



1. A. phrenica inferior. 



2. A. suprarenalis media. 



3. A. renalis. 



4. A. spermatica interna. 



SINGLE BRANCHES. 



1. A. coeliaca. 



2. A. mesenterica superior. 



3. A. mesenterica inferior. 



4. A. sacralis media. 



5. Aa. lumbales. 



With the exception of the middle sacral, which arises from 

 the back of the extremity of the aorta, between the two 

 common iliacs, the single branches have already been de- 

 scribed. The middle sacral artery will be examined when 

 the pelvis minor is dissected. The paired branches may now 

 be examined. 



The Inferior Phrenic Arteries have already been noticed 

 upon the under surface of the diaphragm. They are two in 

 number, and are the first branches which spring from the 

 abdominal aorta. As they pass upwards and forwards they 

 diverge from each other, the artery of the right side passes 

 behind the inferior vena cava, whilst the artery of the left side 

 goes behind the oesophagus. Near the posterior border of 

 the central tendon of the diaphragm each divides into a 

 lateral and a medial branch. The lateral branch proceeds 

 laterally to anastomose with the intercostal arteries, whilst 



