214 



Aorta thoracica. 



560. Segment of the Thoracic 

 Aorta with Injected Vasavasorum. 



View from behind. Natural size. 



The descending thoracic aorta, 

 Aorta thoracica descendens, gives off numerous, 

 but mostly small branches. These are: 



a) The posterior bronchial, Arteriae 

 broncJuales posteriores, to the posterior wall of 

 the bronchial tubes, the right frequently arises 

 from the third or fourth right intercostal artery. 

 The anterior bronchial, Arteriae bron- 

 chialcs anteriores. arise from the internal mam- 

 mary artery. 



b) The o e s o p h a g e a 1, Arteriae oeso- 

 phageae, 2 4 in number. 



c) The meclias tinal, Arteriae media- 

 stinicae, to the structures in the posterior media- 

 stinum. These, as well as the previous, supply also the posterior wall of 

 the pericardium by means of the posterior pericardiac arteries. 



d) The intercostal, Arteriae intercostales, for the nine inferior 

 intercostal spaces and for the lower border of the twelfth rib, the two 

 upper intercostal spaces being supplied by the superior intercostal branch 

 Of the subclavian artery. The left are shorter than the right. Each of 

 these arteries divides into a posterior or dorsal and an anterior or 

 intercostal branch. The dorsal branches pass each between the 

 transverse processes of two vertebrae to the muscles of the back, and also 

 supply the spinal cord and its membranes with branches, which enter through 

 the intervertebral foramina. Each intercostal branch passes forwards 

 to the sternum in the Sulcus costae of the rib above it, sends the supracostal 

 branch to the upper border of the rib below and finally unites with the 

 anterior intercostal branch of the internal mammary artery. The intercostal 

 branches supply the intercostal muscles, the M. peetoralis major, M. ser- 

 ratus marjnus and the costal origins of the abdominal muscles, in the 

 female also the mammary gland. 



