70 TOPOGRAPHIC AND APPLIED ANATOMY. 



FIG. 27. The supraclavicular region. The sternocleidomastoid and the infrahyoid muscles have been removed. 

 FIG. 28. The infraclavicular region. 



division takes place approximately behind the right sternoclavicular articulation. ED.] Upon 

 the left side these two vessels arise separately from the arch of the aorta behind the junction of the 

 first rib with the sternum in this region; they are also covered by both portions of the sterno- 

 cleidomastoid muscle, by the sternoclavicular articulation, and by the origins of the sternohyoid 

 and sternothyroid muscles. The common carotid artery gives off no branches, and, after crossing 

 beneath the omohyoid muscle, appears beneath the inner margin of the sternocleidomastoid. 

 The subclavian artery passes out of the thoracic aperture to the inner side of the dome of the 

 pleura (which encloses the apex of the lung), describes an outward curve, the convexity of which 

 is directed upward, passes behind the anterior scalene muscle, and runs over the first rib in the 

 subclavian groove (the lower broad portion of the scalene slit). The artery consequently reaches 

 the supraclavicular fossa, where its pulsations may be more or less distinctly felt, and then passes 

 beneath the middle of the clavicle and the subclavius muscle,' below which it is known as the 

 axillary artery. With the exception of the posterior scapular, all of the branches of the sub- 

 clavian artery are given off before the vessel passes between the anterior and middle scalene 

 muscles. These branches lie upon the small portion of the artery which is deeply situated behind 

 the clavicular portion of the sternocleidomastoid muscle and are covered by the subclavian vein 

 and its junction with the internal jugular. The branches are: 



1. The vertebral artery (see page 34). 



2. The internal mammary artery (see page 93). 



3. The thyroid axis, which immediately divides into: 



(a) The inferior thyroid artery. This is usually the largest division of the thyroid axis. It 

 runs upward and then inward upon the vertebral column behind the common carotid artery, 

 supplies the pharynx, esophagus, trachea, and larynx (inferior laryngeal artery), and reaches the 

 posterior surface of the thyroid gland. 



(6) The ascending cervical, which is often very small and runs upward upon the origins of 

 the scalene muscles. 



(c) The transversalis colli, which passes through the supraclavicular fossa transversely 

 across the scalene muscles and in front of the brachial plexus to the trapezius muscle. 



(d) The suprascapular, which is frequently an independent branch of the subclavian artery. 

 This vessel runs slightly downward to the upper margin of the scapula and is concealed beneath 

 the clavicle ; it passes over the transverse ligament of the scapula to reach the supraspinous fossa 

 and then skirts the neck of the bone and enters the infraspinous fossa. It supplies the supra- 

 spinatus and infraspinatus muscles and anastomoses with 'the subscapular branch of the axillary 

 artery (see page 74 and Fig. 30). 



4. The costocervical axis, a short trunk which passes posteriorly and divides into: 



(a) The superior intercostal artery (see page 96) for the first one or two intercostal spaces, and 

 (6) The deep cervical artery, which runs posteriorly over the neck of the first rib to supply 

 the deep muscles of the neck and back. 



