591 



Vertebral 

 vein, and 

 branches. 



Internal 

 mammary 

 artery in 

 the neck. 



Thyroid axis 



divides into 

 three. 



Supra- 

 scapular 

 artery. 



Transverse 

 cervical 

 artery : 



offsets, 



size and 

 ending vary. 



Inferior 

 thyroid 

 artery 



gives laryu- 

 geal offset, 



and ascend- 

 ing cervical 

 branch. 



DISSECTION OF THE NECK. 



The vertebral vein issues with its accompanying artery, to which 

 it is here superficial, and descends over the suhclavian artery td 

 join the innominate vein ; it receives the deep cervical vein, and the 

 branch (anterior vertebral vein) that accompanies the ascending 

 cervical artery. 



2. The internal mammary artery leaves the lower part of the sub- 

 clavian artery, and coursing downwards beneath the clavicle, and 

 on the outer side of the innominate vein, enters the thorax between 

 the cartilage of the first rib and the pleura. As the artery dis- 1 

 appears in the chest, it is crossed superficially by the phrenic nerve. 

 The vessel is distributed to the walls of the chest and abdomen ; and 

 its anatomy has been learnt with the dissection of those parts (see 

 p. 440). 



3. Ihyroid axis. This is a short thick trunk (fig. 213) which 

 arises from the front of the subclaviaii artery near the anterior 

 scalenus muscle, and soon divides into three branches one to the 

 thyroid body, and two to the back of the shoulder. 



a. The suprascapular branch courses outwards across the lower 

 part of the neck, behind the clavicle and subclavius muscle, to the 

 superior border of the scapula, and entering the supraspinous fo.-sa 

 is distributed on the dorsum of that bone. The connections of this 

 artery have been more fully seen in the dissection of the back. 



b. The transverse cervical branch, usually larger than the preceding, 

 takes a similar direction, though higher in the neck, and ends 

 beneath the border of the trapezius muscle in superficial cervical 

 and posterior scapular branches as already traced. In its course 

 outwards through the posterior triangular space, this branch 

 crosses in front of the anterior scalenus, the phrenic nerve, and the 

 brachial plexus, but usually behind the omo-hyoid. Some small 

 offsets are supplied by it to the parts in the posterior triangle. 



In many bodies the transverse cervical vessel is of small size, 

 and ends as the superficial cervical artery, while the posterior 

 scapular branch arises separately from the third, or even from the 

 second part of the subclaviaii trunk (fig. 213). 



c. The inferior thyroid artery is the largest offset of the thyroid 

 axis. Directed inwards with a flexuous course to the thyroid body, 

 this branch passes beneath the common carotid artery and the accom- 

 panying vein and nerves, and in front of the longus colli muscle, to 

 the side of the trachea. Behind the lateral lobe of the thyroid 

 body it crosses either in front of or behind the recurrent nerve, and 

 divides into branches which enter the lower part of the gland, and 

 communicate with the superior thyroid and its fellow. 



Near the larynx an inferior laryngeal branch is directed upwards 

 with the nerve of the same name, and other offsets are furnished to 

 the trachea and oesophagus, and to the neighbouring muscles. 



The ascending cervical branch is directed upwards between the 

 origins of the scalenus anticus and rectus capitis anticus major, and 

 ends in branches to those muscles and the posterior triangle of 

 the neck. Some small spinal offsets enter the spinal canal through 

 the inter vertebral foramina. 



