THE LUMBAR ARTERIES 593 



2. THE LUMBAR ARTERIES 



The lumbar arteries [aa. lumbales] (fig. 479), usually eight in number, four on 

 each side, come off in pairs from the posterior aspect of the abdominal aorta, 

 opposite the bodies of the four upper lumbar vertebrae. A fifth pair of lumbar 

 arteries, generally of small size, frequently arises from the middle sacral artery 

 opposite the fifth lumbar vertebra. The lumbar arteries, which are rather longer 

 on the 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 around the bodies of the 

 vertebrae to the space between the transverse processes, where they give off each a 

 dorsal branch, and then, coursing forward between the abdominal muscles, termi- 

 nate, by anastomosing with the other arteries of the abdominal wall. 



Relations. — As they wind around the bodies of the vertebrae they pass beneath the chain of 

 the sympathetic nerve trunk, and the upper two beneath the crura of the diaphragm. The 

 right arteries also pass beneath the vena cava inferior, and the two upper on that side beneath 

 the receptaculum chyli. The arteries on both sides then dip beneath the tendinous arch thrown 

 across the sides of the bodies of the vertebrae by the psoas, and continue beneath this muscle 

 until they arrive at the interval between the transverse processes of the vertebrae and the 

 medialedgeof the quadratus lumborum. While under cover of the psoas they are accompanied 

 by two slender filaments of the sympathetic nerve and by the lumbar veins. A little anterior 

 to the transverse processes they are crossed by branches of the lumbar plexus, and here usually 

 cross in front of the ascending lumbar vein. They now pass behind the quadratus lumborum, 

 with the exception sometimes of the last, which may pass in front of the muscle. At the lateral 

 edge of the quadratus they run between the transversus and the internal oblique, and then, after 

 perforating the internal oblique between the internal and external oblique. Finally, much 

 diminished in size, the^^ enter the rectus, and give off one or more anterior cutaneous branches, 

 which accompany the last thoracic and the iUo-hypogastric nerves to the skin. They 

 anastomose with the lower intercostals, iUo-lumbar, deep circumflex iliac, and inf. epigastric 

 arteries. 



The branches of the lumbar arteries are : — 



(a) Vertebral branches which supply the bodies of the vertebrae and their connecting 

 ligaments. 



(6) Muscular branches to the psoas, quadratus lumborum, and oblique muscles of the 

 abdomen. 



(c) The dorsal branch [r. dorsalis]. This is of large size, and passes backward in company 

 with the dorsal nerve between the transverse processes above and below, the intertransversalis 

 medially and the quadratus lumborum laterallj^ to the muscles of the back. On reaching the 

 interval between the longissimus dorsi and multifidus spinae, it divides into a lateral and a 

 medial branch. The former ends in the multifidus, the latter and larger suppUes the sacro- 

 spinalis, and gives branches which accompany the termination of the dorsal nerves to the skin. 

 Just before the artery passes between the transverse processes it gives off a spinal branch [r. 

 spinalis], which accompanies the lumbar nerve through the intervertebral foramen into the 

 vertebral canal (see p. 590). 



(d) Renal branches of small size pass forward in front of the quadratus lumborum to the 

 capsule of the kidney. They anastomose with the renal artery. A communication is thus 

 established between the renal arteries and the arteries supplying the lumbar region. 



B. The Visceral Branches of the Abdominal Aorta 



THE CCELIAC ARTERY 



The c celiac artery [a. cceliaca] — or c celiac axis, as it is commonly called, 

 because it breaks up simultaneously into three branches which radiate from it 

 like the spokes of a wheel from the axle — ^is a short thick trunk given off from 

 the front of the aorta between the medial crura of the diaphragm a little below 

 the aortic opening. It passes horizontally forward above the upper margin 

 of the pancreas for about half an inch, and then breaks up into three branches 

 for the supply of the stomach, duodenum, spleen, pancreas, liver, and gall- 

 bladder (fig. 481). 



Relations. — In front is the lesser omentum; behind, the aorta; above, the right lobe of the 

 hver; below, the pancreas; to the right, the right coeliac (semilunar) ganglion and caudate lobe 

 of the liver; to the left, the left coeliac (semilunar) ganglion and the cardiac end of the stomach. 

 It is closely surrounded by the dense coeliac (solar) plexus of sympathetic nerves. 



Branches of the cceliac artery. — The coeliac artery divides into the left 

 gastric, the hepatic, and the splenic arteries. 



1. The Left Gastric Artery 



The left gastric [a. gastrica sinistra] (fig. 481), the smallest of the three 

 branches into which the coeliac artery divides, courses at first upward and to the 



