THORACIC AORTA 



549 



abdominal muscles, and anastomose with the deej) epigastric artery from the 

 external iliac, and with the luml)ar arteries from the al^dominal aorta. 



The intercostal arteries give oft" the following branches: — 



(a) The dorsal branch. — This large branch is given off from the intercostals 

 opposite the quadrilateral space l^ounded by the transverse process of the vertebra 

 above, the neck of the rib below, the body of the vertebra internally, and the 

 superior eosto-trans verse ligament externally. Passing backwards towards this space 

 with the dorsal branch of tlie corresponding intercostal nerve, the dorsal branch 

 divides oi)p()site the intervertebral foramen into a spinal and a nmscular Itranch. 

 (i) The spinal branch enters the intervertebral foramen along with the undivided 

 trunk of the intercostal nerve, and subdivides into three branches: — («) an anterior, 

 or preneural, which ramifies on the back of the body of the vertebra and anas- 

 tomoses wdth the corresponding vessels above and below; (/5) a posterior, or retro- 



FiG. 362. — Scheme of Intercostal Artery. (Walsbam.) 



liongissimus dorsi 



External division oj muscular branch 

 I lUo-costalis 



Internal dirision of muscular branch 

 Semispinalis dorai and multifldua spinae 



Posterior spinal arteries 



Retroneural branch - 



Medullary branch 



Preneural branch 



SPISAL CORD 



Anterior spinal artery 



Intercostal artery 



Vena azygos minor 



Vena azygos major 



THORACIC DUCT 



(ESOPHAGUS 



Spinal branch 



Dorsal branch 



Anterior intercostal 



Internal mammary artery 



Anterior per/orating branch of 

 internal mammary artery 



SYMPATHETIC 



Lower branch of 

 aortic intercostal 



Upper or main 

 branch of aortic 

 intercostal 



Lateral cutaneous 

 branch 



Lower branch of 

 anterior intercostal 



Mammary glandular 



branch 

 I'j'per or main 



branch of anterior 



intercostal 



neural, which ramifies over the ])ack of the spinal canal and also anastomoses with 

 the like artery above and below; and (y) a middle or medullary, which, passing 

 inwards in the sheath of dura mater to the spinal cord, anastomoses with the 

 anterior s})inal artery in front, and with the posterior s])inal artery behind. ( ii) The 

 muscular branch passes backwards through the quadrilateral space, and soon 

 sultdivides into an external and internal branch. The former passes between the 

 longissimus dorsi and ilio-costalis, and, after supplying these muscles, gives cuta- 

 neous offsets to the integuments. The latter or internal branch pierces the multi- 

 fidus spinse, and, emerging between the longissimus dorsi and semispinalis dorsi 

 near the spinous processes, gives cutaneous offsets to the skin. It supplies the 

 nmscles in its course 



(h) The collateral intercostal branch comes off from the intercostal artery 

 near the angle of the rib above, and descends to the upper border of the rib l)elijw, 



