ABDOMINAL AORTA 149 



The Unpaired Parietal Branch. The Middle Sacral artery 

 is a small artery arising from the back of the aorta just before 

 its bifurcation. It passes down the middle of the sacrum, sup- 

 plying the muscles and joints in the vicinity. 



The Paired Visceral Branches. The Suprarenal arteries 

 consist of three pairs of arteries for the supply of the suprar- 

 renal capsule. The middle pair arises from the aorta direct, 

 the others are branches of adjacent arteries. 



The Renal arteries arise opposite the second lumbar vertebra 

 just below the superior mesenteric. Each passes transversely 

 outwards over the crus of the diaphragm and the upper part 

 of psoas to the hilum of the kidney. The right artery is a 

 little longer than the left and often lower in position. It passes 

 behind the inferior vena cava, the head of the pancreas, and 

 the middle of the duodenum. The left artery lies behind the 

 pancreas. 



The Spermatic or Ovarian arteries arise just below the renal 

 arteries. The spermatic arteries run downward and outwards 

 through the inguinal canal to supply the testicles. The ovarian 

 arteries are much shorter, and pass straight down into the pelvis 

 and supply the ovaries. 



The Unpaired Visceral Branches. The Coeliac Axis arises 

 from the front of the aorta just after it has entered the ab- 

 domen. It is very short (about half an inch), and divides 

 almost at once into three branches : 



1. Gastric. 



2. Splenic. 



3. Hepatic. 



The Gastric artery runs upwards and to the left to the oeso- 

 phagus, and passes along the smaller curvature of the stomach 

 between the layers of the small omentum to join the pylorio 

 branch of the hepatic artery. 



The Splenic artery runs behind the stomach along the upper 

 border of the pancreas. It passes between the two layers of 

 the lieno-renal ligament and enters the hilum of the spleen. 



The Hepatic artery runs along the head of the pancreas to 

 the first part of the duodenum. It then passes upwards to the 



