THE VASCULAR SYSTEM. 



133 



blood may not be forced back into the heart by the con- 

 traction of the muscular coat of the arteries* 



The branches of the thoracic aorta are as follows : the 

 right and left coronary, arising from the aorta immediately 

 beyond its exit from the ventricle, are distributed to the 

 walls of the heart. From the arch of the aorta arise 

 two large branches; first, the innominate, giving origin to 

 the right subclavian supplying blood to the arm, and the 

 right and left carotids supply- 

 ing the head and neck; and 

 second, the left subclavian, sup- 

 plying the left arm, brain, and 

 sternum (Fig. 72). Ten pairs 

 of intercostal arteries supply 

 the intercostal spaces, muscles, 

 of the back, and the spinal cord. 

 Two bronchial arteries go to 

 the lung tissue. Two to four 

 esophageal arteries are distrib- 

 uted to the esophagus. Two 

 or three pairs of lumbar ar- 

 teries pierce the muscles of the 

 back. 



FIG. 72. CHIEF ARTERIES OF THE 

 TRUNK, VENTRAL ASPECT. 



ar, Arch of the aorta; be, innomi- 

 nate; ce, cceliac axis; cd, cau- 

 dal; e, gastric; /, gastric; gr, 

 gastric ; gas, gastroduodenalis ; hp, 

 hepatic ; ht, location of heart ; ten, 

 intercostals ; ic, external iliac ; it, 

 internal iliac ; il, iliolumbar ; im, 

 inferior mesenteric; Is, left sub- 

 clavian; //>/, left pulmonary; m, 

 splenic ; o, splenic ; r, right pul- 

 monary; re, renal; sp, splenic 

 trunk; sms, superior mesenteric; 

 sm, spermatic or ovarian; s, ad- 

 renolumbalis ; i, 2, 3, 4, 5, and 6, 

 lumbar arteries. 



