PHRENIC AND LUMBAR 553 



The parietal branches are distributed to the abdominal walls. They are the 

 right and left })lnvnics. and the four right and left lumbars. 



Tiie visceral branches supply the viscera. Three of these are given oft" 

 singly from the front of the aorta, namely, the ea4iac axis, the sujierior mesenteric 

 and the inferior mesenteric; and three are given oft' in pairs, namely, the two 

 suprarenals. the two rciials, ami the two spermatics. 



The terminal branches are the middle sacral and the right and left common 

 iliac arteries. 



A. The Parietal BRANCHFi? of the Abdominal Aorta 



1. THE PHRENIC ARTERIES 



The right and left phrenic arteries — sometimes called the inferior phrenic to 

 distinguish them from the diaphragmatic branches of the internal manmiary and 

 thoracic aorta — usually arise from the aorta as it passes between the crura of the 

 diaphragm either as a common trunk or as separate vessels. At times they come 

 off as a common trunk from the coeliac axis; or either the right or left vessel may 

 come from this artery, or from other of the upper branches of the abdominal 

 aorta. 



The right phrenic passes (fig. 363) over the right crus of the diaphragm behind 

 the vena cava, and then upwards and to the right Ijetween the central and right 

 leaflets of the central tendon of the muscle, where it divides into an anterior and 

 a posterior branch. The former courses forwards and inwards, and anastomoses 

 with the anterior branch of the left phrenic, Avith the musculo-phrenic branches of 

 the internal mammary, and with the superior phrenic arteries; the latter passes 

 outwards and liackwards towards the ribs, and anastomoses with the intercostal 

 arteries. Besides the two terminal branches and branches for the supply <»f tln' 

 diaphragm itself, the right phrenic gives off the following: — (1 ) Right superior 

 suprarenal, to the right suprarenal capsule; (2) caval, to the vena cava; (3) 

 hepatic, to the liver; and (4) pericardiac, to the pericardium. 



The left phrenic crosses the left crus of the diaphragm behind the cesophagus, 

 and then runs l)etween the left and central leaflets of the tendon, dividing like the 

 right into an anterior and a posterior branch. The former runs forwards and 

 inwards, and anastomoses with the anterior branch of the right phrenic, the left 

 musculo-phrenic from the internal mammary, and the suj^erior ^jhrenic artery. The 

 latter courses outwards and Ijackwards towards the ribs, and anastomoses with the 

 intercostal arteries. In addition to the terminal branches, and branches to 

 the diajjhragm itself, the left phrenic gives off: — (1) CEsophageal branches ti» the 

 ceso])hagus. where they anastomose with the other (es(»]ihagcal branclu-s; {'!) left 

 superior suprarenal, to the left suprarenal l)ody; (3) splenic, to the spleen; and 

 (4) pericardiac, which perforate the diaphragm and anastomose with the other 

 pericardiac arteries. 



The variations in the origin of the phrenic arteries are very nuiiierou?>. The chief have been 

 alluded to in the general description of the vessels. 



2. THE LPMBAR ARTERIES 



The lumbar arteries (figs. 360, 363), usually eight in number, four on each 

 side, con)e oft" in pairs from the ])0.sterior aspect of the abdominal aorta, opposite 

 the bodies of the four ui)i)er luml)ar vertebrae A fifth ])air of lumbar arteries, 

 generally of small size, are frequently given off from the middle sacral opposite the 

 fifth lumbar vertel)ra. The lumbar arteries, whicli are rathi-r longer on tlie right 

 than on the left side, in consequence of the aorta lying a little to the left of the 

 median line, wind more or less transversely outwards round the bodies of the ver- 

 tel^rse to the interval between the transverse processes, where they give off a dorsal 

 branch, and then, coursing forwards between the alxlominal nuiscles, terminate liy 



