632 



THE VASCULAR SYSTEMS 



and branches of the posterior scapular arteries. Besides distributing branches 

 to the Sternomastoid, Subclavius, and neighboring muscles, it gives off a supra- 

 sternal branch, which crosses over the sternal end of the clavicle to the skin of the 

 upper part of the chest; and a supra-aero mial branch (ramus acromialis], which, 

 piercing the Trapezius muscle, supplies the skin over the acromion, anastomosing 

 with a branch of the acromiothoracic artery. A small subscapular branch is given 

 off as the artery passes over the transverse ligament of the scapula ; it descends into 

 the subscapular fossa, ramifies beneath the Subscapular muscle, and anastomoses 

 with the posterior and subscapular arteries. The suprascapular artery also sends 

 branches to the acromioclavicular and shoulder-joints, and a nutrient artery to 

 the clavicle. 



Posterior scapular. 



Suprascapular. 



Acromial branch of 



acromiothoracic 



I 



Anterior 

 circumflex. 



^Termination of 

 subscapular. 



FIG. 458. The scapular and circumflex arteries. 



The transverse cervical artery (a. transversa colli) (Fig. 438), larger than the 

 suprascapular, passes transversely outward, across the upper part of the sub- 

 clavian triangle, to the anterior margin of the Trapezius muscle, beneath which 

 it divides into two branches, the superficial cervical and the posterior scapular. 

 In its passage across the neck it crosses in front of the phrenic nerve, Scaleni 

 muscles, and the brachial plexus, between the divisions of which it sometimes 

 passes, and is covered by the Platysma, Sternomastoid, Omohyoid, and Trapezius 

 muscles. 



The superficial cervical (ramus ascendens] ascends beneath the anterior margin 

 of the Trapezius, distributing branches to it and to the neighboring muscles and 

 lymph nodes in the neck, and anastomosing with the superficial branch of the 

 arteria princeps cervicis. 



The posterior scapular (ramus descendens) (Fig. 458) passes beneath the Levator 

 anguli scapulae muscle to the superior angle of the scapula, and then descends 

 along the posterior border of that bone as far as the inferior angle. In its course 

 it is covered by the Rhomboid muscles, supplying them and the Latissimus dorsi 

 and Trapezius, and anastomosing with the suprascapular and subscapular arteries, 

 and with the posterior branches of some of the intercostal arteries. 



Peculiarities. The superficial cervical frequently arises as a separate branch from the thy- 

 roid axis; and the posterior scapular, from the third, more rarely from the second, part of the 

 subclavian. 



