332 BRANCHES OF THE ABDOMINAL AORTA. 



size and origin. They are distributed to the bronchial glands and 

 tubes, and send branches to the oesophagus, pericardium, and left 

 auricle of the heart. These are the nutritious vessels of the lungs. 



The CEsoPHAGEAL ARTERIES are numerous small branches ; they 

 arise from the anterior part of the aorta, are distributed to the oeso- 

 phagus, and establish a chain of anastomoses along that tube : the 

 superior inosculate with the bronchial arteries, and with oesophageal 

 branches of the inferior thyroid arteries ; and the inferior with similar 

 branches of the phrenic and gastric- arteries. 



The INTERCOSTAL, or posterior intercostal arteries, arise from the 

 posterior part of the aorta ; they are nine in number on each side, the 

 two superior spaces being supplied by the superior intercostal artery, 

 a branch of the subclavian. The right intercostals are longer than the 

 left, on account of the position of the aorta. They ascend somewhat 

 obliquely from their origin, and cross the vertebral column behind the 

 thoracic duct, vena azygos major, and sympathetic nerve, to the inter- 

 costal spaces, the left passing beneath the superior intercostal vein, the 

 vena azygos minor and sympathetic. In the intercostal spaces, or 

 rather, upon the external intercostal muscles, each artery gives off a 

 dorsal branch^ which passes back between the transverse processes of 

 the vertebrae, lying internally to the middle costo- trans verse ligament, 

 and divides into a spinal branch, which supplies the spinal cord and 

 vertebrae, and a muscular branch which is distributed to the muscles 

 and integument of the back. The artery then comes into relation 

 with its vein and nerve, the former being above and the latter below, 

 and divides into two branches which run along the borders of conti- 

 guous ribs between the two planes of intercostal muscles, and ana- 

 stomose with the anterior intercostal arteries, branches of the internal 

 mammary. The branch corresponding with the lower border of each 

 rib is the larger of the two. They are protected from pressure during 

 the action of the intercostal muscles, by little tendinous arches thrown 

 across them and attached by each extremity to the bone. 



BRANCHES OF THE ABDOMINAL AORTA. 



Phrenic, 



( Gastric, 

 Coeliac axis < Hepatic, 



( Splenic. 



Superior mesenteric, 

 Spermatic, 

 Inferior mesenteric, 

 Supra-renal, 

 Renal, 

 Lumbar, 

 Sacra media. 



