582 



THE VASCULAR SYSTEMS 



THE ARCH OF THE AORTA (ARCUS AORTAE). 



The arch, or transverse aorta, commences at the level of the upper border of the 

 second chondrosternal articulation of the right side, and passes at first upward, 

 backward, and to the left in front of the trachea; it is then directed backward on the 

 left side of the trachea, and finally passes downward on the left side of the body of 

 the fourth thoracic vertebra, at the lower border of which it becomes continuous with 



the descending aorta. It thus 

 forms two curvatures, one with 

 its convexity upward, the other 

 with its convexity forward and 

 to the left. Its upper border 

 THORACIC DUCT -~u ,<^=^c ^^/"H VAGUS NERVE i s usua liy about an inch below 



the upper margin of the ster- 



VENA AZYGOS MAJOR 



TRACHEA 

 JUST ABOVE DIV 



DESCENDING 

 PORTION OF ARCH 



SUPERIO! 

 VENA CA 1 

 RIGHT PLEU 



INTERNAL 

 MAMMARY ARTERY 



LEFT PLEURA 



LEFT PHRENIC NERVE 



FIG. 435. Horizontal section through the fourth thoracic 

 vertebra upper surface of the lower segment. The cut is made 

 at the lower part of the transverse portion of the aortic arch. 



num. 



Relations. The arch of the aorta 

 is covered in front by the pleurae and 

 anterior margins of the lungs, and 

 by the remains of the thymus gland. 

 As the vessel runs backward its left 

 side is in contact with the left lung 

 and pleura. Passing downward on 

 the left side of this part of the arch 

 are four nerves; in order from be- 

 fore backward these are the left 

 phrenic, the inferior cervical cardiac branch of the left vagus, the superior cardiac branch of the 

 left sympathetic, and the trunk of the left vagus. As the last nerve crosses the arch it gives off 

 its recurrent laryngeal branch, which hooks around below the vessel and then passes upward 

 on its right side. The left superior intercostal vein runs obliquely upward and forward, on 

 the left side of the arch between the phrenic and vagus nerves. On the right are the deep car- 

 diac plexus, the left recurrent laryngeal nerve, the oesophagus, and thoracic duct; the trachea lies 

 behind and to the right of the vessel. Above are the innominate, left common carotid, and 

 left subclavian arteries, which arise from the convexity of the arch and are crossed close to their 

 origins by the left innominate vein. Below are the bifurcation of the pulmonary artery, the left 

 bronchus, the ligamentum arteriosum, the superficial cardiac plexus, and the left recurrent 

 laryngeal nerve. As already stated, the ligamentum arteriosum connects the commencement 

 of the left pulmonary artery to the aortic arch. 



PLAN OF THE RELATIONS OF THE ARCH OF THE AORTA. 



Above. 



Left innominate vein. 

 Innominate artery. 

 Left carotid. 

 Left subclavian. 



In Front. 



Pleurae and lungs. 

 Remains of thymus gland. 

 Left vagus nerve. 

 Left phrenic nerve. 

 Superficial cardiac nerves. 

 Left superior intercostal vein. 



Behind. 



Trachea. 



Deep cardiac plexus. 



(Esophagus. 



Thoracic duct. 



Left recurrent nerve. 



Below. 



Bifurcation of pulmonary artery. 

 Remains of ductus arteriosus. 

 Superficial cardiac plexus. 

 Left recurrent nerve. 

 Left bronchus. 



