482 



DISSECTION OF THE THORAX. 



two left ; 



one right. 



Pericardial 

 branches. 



(Esophageal 

 branches. 



Mediastinal 

 branches. 



Intercostal 

 arteries : 



number ; 



course to 

 intercostal 

 spaces ; 



right 

 longer. 



The anterior 

 branch 



occupies 



intercostal 



space 



with vein 

 and nerve. 



Offsets. 



Anasto- 



Posterior 

 branch 

 turns to 

 the back. 



There are two arteries for the left lung (superior and inferior), 

 which arise from the front of the aorta at a short distance from 

 each other. 



The artery of the right lung arises in common with one of the 

 left bronchial arteries (superior), or from the first intercostal artery 

 of the right side. 



b. The pericardial branches are some irregular twigs, which are 

 furnished to the posterior part of the pericardial bag. 



c. The cesophageal branches are four or five in number, and ramify 

 in the gullet, forming anastomoses with one another ; above, they 

 communicate with branches of the inferior thyroid artery ; and 

 below, with twigs of the coronary artery of the stomach. 



d. Small mediastinal branches (posterior) supply the areolar tissue 

 and the glands in the interpleural space. 



e. The INTERCOSTAL ARTERIES are nine on each side, and pass to 

 the same number of lower intercostal spaces. Branches are supplied 

 to the upper two spaces from the intercostal artery of the subclavian 

 trunk. 



These vessels arise from the posterior part of the aorta, and run 

 outwards on the bodies of the vertebrae, beneath the cord of the 

 sympathetic nerve, to the intercostal spaces, where each divides into 

 an anterior and a posterior branch. In this course the upper arteries 

 have a somewhat oblique direction ; and as the aorta lies on the 

 left of the spine, the right vessels are the longer, and run also 

 beneath the oesophagus, the thoracic duct, and the large azygos 

 vein. Many twigs are supplied to the bodies of the vertebrae. 



In the intercostal space, the anterior branch, the larger of the two, 

 continues onwards between the muscular strata to the front of the 

 chest, where it ends by anastomosing with an intercostal branch of 

 the internal mammary artery (p. 441). At first the artery 

 lies in the middle of the space, beneath the pleura, and resting 

 on the external intercostal muscle ; but near the angle of the 

 rib it ascends to the upper boundary. Accompanying the artery 

 are the intercostal vein and nerve, the vein being commonly 

 above, and the nerve below it ; but in the upper spaces the nerve 

 is, at first, higher than the artery. 



Branches are furnished to the intercostal muscles, and to the ribs. 

 Near the angle of the rib a larger (collateral) branch is given off, 

 which runs forwards along the lower border of the space, and joins 

 in front a branch of the internal mammary ; and about the middle 

 (from front to back) of the intercostal space a superficial twig arises, 

 to accompany the lateral cutaneous nerve. 



The highest artery of the aortic set of intercostals anastomoses 

 with the superior intercostal branch of the subclavian artery. The 

 lowest two are continued in front into the abdominal wall, where 

 they lie between the internal oblique and transversalis muscles, and 

 anastomose with the epigastric and lumbar arteries. 



The posterior branch turns backwards between the vertebra and 

 the superior costo-transverse ligament, and is distributed in the 

 back. As it passes the intervertebral foramen it furnishes a small 



