ARTERIAL SYSTEM. 



DISTRIBUTION OF ARTERIES. 



The blood is propelled by the heart 

 through the gi-eat aorta, which rises out of 

 the base of the left ventricle, in the space 

 between the left auricle and the pulmonary- 

 artery. The branches furnished by the 

 main trunk are the coronary arteries. The 

 right coronary artery emerges from between 

 the pulmonary and right auricle, winds round 

 the fissure separating that cavity from the 

 right ventricle, and turns down under the 

 termination of the vena cava; and distri- 

 butes ramifications in its course, which 

 penetTate the substance of the parietes, 

 and end in spiral branches. The left coro- 

 nary artery, in passing out between the 

 pulmonary artery and left auricle, sends 

 off a large branch, which encircles the 

 other auricle ; it then takes its course down- 

 ward, and ends in spiral ramifications. 



ANTERIOR AORTA. 



This is a shorter division of the main 

 trunk. The course of this vessel is under 

 the windpipe ; it gives origin to those large 

 arteries which are distributed over the 

 breast, head, neck, brain, and anterior ex- 

 tremities. It divides, at a short distance 

 from the heart, into the right and left ar- 

 teria innominata ; the right is considerably 

 longer than the left, and measures nearly as 

 much again in circumference ; it forms the 

 trunk from which the two carotid arteries 

 spring; the left terminates in the following 

 vessels : * 



1. The dorsal artery. 2. Posterior cervi- 

 cal. 3. Vertebral. 4. Internal pectoral. 

 5. External pectoral. 6. Inferior cervical. 



* The vertebral artery, forming the basilar, gives off 

 the posterior cerebcllal, anterior cerebellal, posterior cere- 

 bral, and the circular arteriosus. 



7. Axillary. Each of these arteries ramify 

 and anastomose with others, and are dis- 

 tributed to muscular and adipose substance. 

 From the axillary artery spring all the ar- 

 teries of the fore extremity. This vessel 

 can only be seen by detaching the shoulder 

 from the body. It arises within the chest, 

 from the arteria innominata ; gains exit by 

 making a sudden turn around the first rib, 

 rather below its middle, crossing the lower 

 border of the scalenus in the turn ; it is 

 first directed outward in this flexure, and 

 then backward, and at length reaches the 

 inner part of the head of the humerus, 

 where it makes another turn backward, and 

 afterwards takes the name of the brachial 

 artery. Its branches are — 1. The external 

 thoracic. 2. The internal thoracic, which 

 runs to the point of the shoulder, and gives 

 its branches to the levator humeri and 

 shoulder joint. 3. The dorsalis scapula) 

 ascends, in a flexuous manner, to the 

 shoulder joint, crossing the insertion of the 

 subscapularis. It runs for a short distance 

 along the ribs. 4. The subscapularis, a 

 large artery, which also arises from the 

 upper part of the trunk, but near to its ter- 

 mination. It passes along the ribs, screened 

 from view by the edges of the subscapu- 

 laris and teres major, to both of which 

 muscles it detaches several small branches, 

 and ends near the lower angle of the bone ; 

 it also gives off several branches to the 

 triceps and panniculus. 5. The humeral. 



The humeral artery descends from the 

 inner and back part of the head of the os 

 humeri, in an oblique direction on the body 

 of the bone, where it divides into the ulnar, 

 spiral, and radial arteries. On its inner 

 side, it has the spu'al and ulnar ners^es ; in 

 front, the radial nerve; and behind, the 



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