

THE ABDOMINAL AORTA 659 



Mammary branches are given off by the intercostal arteries in the third, fourth, 

 and fifth spaces. They supply the mammary gland, and increase considerably 

 in size during the period of lactation. 



Applied Anatomy. The position of the intercostal vessels should be borne in mind in 

 performing the operation of paracentesis thoracic. The puncture should never be made nearer 

 the middle line posteriorly than the angle of the rib~ as the artery crosses the space internal to" 

 Tnis point. In the lateral portion of the thorax, where the puncture is usually made, the artery 

 lies at the upper part of the intercostal space, and therefore the puncture should be made just 

 above the upper border of the rib forming the lower boundary of the space. 



The Abdominal Aorta (aorta abdominalis) (Fig. 467). The abdominal aorta 

 commences at the aortic opening of the Diaphragm, in front of the lower border 

 of the body of the last thoracic vertebra, and, descending a little to the left side of 

 the vertebral column, terminates on the body of the fourth lumbar vertebra, com- 

 monly a little to the left of the middle line, 1 by dividing into the two common 

 iliac arteries. It diminishes rapidly in size, in consequence of the many large 

 branches which it gives off. As it lies upon the bodies of the vertebrse, the 

 curve which it describes is convex forward, the greatest convexity corresponding 

 to the third lumbar vertebra, which is a little above and to the left side of the 

 umbilicus. 



Relations. It is covered, in front, by the lesser omentum and stomach, behind which are 

 the branches of the coeliac axis and the solar plexus; below these, by the splenic vein, the pan- 

 creas, the left renal vein, the transverse portion of the duodenum, the mesentery, and aortic 

 plexus. Behind, it is separated from the lumbar vertebrae and intervening disks by the anterior 

 common ligament and left lumbar veins. On the right side it is in relation with the inferior 

 vena cava (the right cms of the Diaphragm being interposed above), the vena azygos major, 

 thoracic duct, and right semilunar ganglion; on the left side, with the gangliated cord of the 

 sympathetic and left semilunar ganglion. 



PLAN OF THE RELATIONS OF THE ABDOMINAL AORTA. 



In front. 



Lesser omentum and stomach. 

 Branches of the coeliac axis and solar plexus. 

 Splenic vein. 

 Pancreas. 

 Left renal vein. 

 Transverse duodenum. 

 Mesentery. 

 Aortic plexus. 

 Right side. Left side. 



Right crus of Diaphragm. 7 \ Gangliated cord. 



Inferior vena cava. / Abdominal | Left semilunar ganglion. 



Vena azygos major. 



Thoracic duct. 



Right semilunar ganglion. 



Behind. 



Left lumbar veins. 

 Vertebral column. 



Surface Marking. In order to map out the abdominal aorta on the surface of the abdomen, 

 a line must be drawn from the middle line of the body, on a level with the costal extremity of 

 the seventh costal cartilage, downward and slightly to the left, so that it just skirts the umbilicus, 

 to a zone drawn around the body opposite the highest point of the crest of the ilium. This point 



1 Lord Lister, having accurately examined 30 bodies in order to 'ascertain the exact point of termination of 

 this vessel, found it "either absolutely, or almost absolutely, mesal in 1.5. while in 13 it deviated more or less 

 to the left, and in 2 was slightly to the right" (System of Surgery, edited by T. Holmes, 2d ed. , vol. v, p 652). 



