Aorta abdominalis. 



223 



569. Course and Ramification of the Abdominal 



Aorta. Specimen from a child. Natural size. 



4. The lumbar arteries, Arteriae lunibales, are five in number 

 on each side and arise from the back part of the aorta; they pass out- 

 wards behind the psoas muscle. Each artery divides into a posterior 

 or dorsal branch, which, with its spinal branch is distributed to 

 the spinal cord and its membranes, and an anterior branch for the 

 broad abdominal muscles. If the artery which runs along the lower 

 border of the twelfth rib is counted as an intercostal artery, there are 

 only four lumbar arteries. 



In front of the fourth lumbar vertebra the abdominal aorta divides 

 into the two common iliac arteries, Arteriae iliacae communes. These 

 pass downwards towards the sacro-iliac symphisis and divide opposite 

 the promontory into the external iliac or crural and the i n t e r- 

 nal iliac or hypogastric arteries. Between both common iliac 

 arteries the Art. sacralis media, which passes down to the coccyx, arises ; 

 it gives off lateral branches, and partly supplies the M. psoas magnus, the 

 M. iliacus internus and the rectum. 



