470 



THE ARTERIES 



The Descending Portion of the Arch of the Aorta 



The descending portion of the arch of the aorta, morphologically a ])art of the 

 ])rimitive dorsal aorta, descends by the left side of the body of the fourth and fifth 

 thoracic vertebrae, and ends at the lower border of the latter in the thoracic aorta. 



Just below the sj^ot where the ductus arteriosus (the fifth left arch) joins the 

 aorta, a constriction (the aortic isthmus ) is at times met with, and below this again 

 a dilatation of a fusiform ^^hape (the aortic spindle ). 



Relations. — In front, it is in contact with the reflexion of the left pleura and 

 the root of the left lung (rig. 325). 



Fig. 324. —The Heart and Great Vessels, with the Eoot of the Lungs, 

 SEEN FROM BEHIND. (St. Bartholomew's Hospital jMuseuni.) 



dSOPHAGUS 

 TRACHEA 



Innoviinale artery 



RIGHT 

 PXE I \M(t G A S TRIC 



XER VE 

 Vena catu stiperior 



Intercostal artery 



RIGHT BRONCHUS 



Intercostal artery 



Bronchial artery 



POSTERIOR PUL- 

 MONARY PLEXUS 



Rir/ht pidmoniiry artery 

 Rhjltt pulmonary vein 



Vena azygos major 

 RIGHT PLEURA 

 Left auricle 



THORACIC DUCT 



Left subclavian artery 



LEFT PNEUMO- 



GASTRIC NERVE 



LEFT RECURRENT 



LARYNGEAL NERVE 



Intercostal artery 



Pulmonary artery 



BRONCHIAL GLANDS 

 Intercostal urterh — 

 LEFT BRONCHUS 



r . , ■ \h% 

 Lei t pulmonary rein L J ^^ 



Descending aorta 



LEFT PLEURA 



Oblique vein 



Left coronary artery 



Coronary sinus 



Left marginal braiich of 

 left coronary artery 



Ventricular branches of 

 coronary artery 



Left ventricle 



Posterior cardiac rein 



Posterior interventricular 

 branch of right coronary 

 artery 



Behind, it is in relation with the left side of the bodies of the fourth and fifth 

 thoracic vertel)i\ne and the ])leura. 



To the right side are the o^-sophagus and thoracic duct, and the fourth and fifth 

 thoracic vertebnr. 



To the left side are the left pleura and lung. 



Variations in the Arch of the Aorta 



The variations that have boon met with in the aortic arch are very niunorous. Only the 

 chief can bo hero montioneil. They may lie divideil into: — 1. Variations in the arch itself; 

 and 2. Variations in the number and arrangement of the three chief branches. The variations 

 in the coronary arteries are describeil under Coronary Arteries, page 473. 



