424 



THE SUBCLAVIAN ARTERIES. 



cervical artery. In some cases the axis is absent, the three branches arising separately from 

 the subclavian. (On the various modes of origin of the branches usually derived from the 

 thyroid axis, and their relative frequency, see " Second Report of Committee of Collective 

 Investigation of Anat. Soc.," 1890-91, by Arthur Thomson, Journ. Anat., xxvi.) 



A. The inferior thyroid artery (iv) (fig. 355, p. 433) passes directly upwards 

 in front of the vertebral artery to about the level of the cricoid cartilage, where it 

 bends inwards and downwards behind the sheath of the large cervical vessels, and 

 also behind the sympathetic nerve, the middle cervical ganglion of which, when 

 present, often rests upon this vessel. Then making another curve in the opposite 

 direction, the artery divides behind the lower part of the lateral lobe of the thyroid 

 body into two branches, a superior which ascends to supply the hinder part, and an 

 inferior distributed to the lower end of the lobe. The artery may cross either in 

 front of or behind the recurrent laryngeal nerve, the former especially frequently on 



Fig. 352. DISTRIBUTION OP THE INFERIOR 

 THYROID ARTERY. (Modified from Streck- 

 i.) (G. D. T.) 



The lateral lobes of the thyroid body are 

 drawn outwards to show the ramifications of 

 the artery. *, branch of artery piercing the 

 suspensory ligament of the gland to reach the 

 isthmus. 



the left side ; or the nerve may lie 

 between the divisions of the vessel. 1 

 The glandular branches of the artery 

 communicate with those of the superior 

 thyroid artery, and with the corre- 

 sponding artery of the other side. 



Branches. (a) Muscular branches 

 to the scalenus anticus, longus colli, 

 inferior constrictor of the pharynx, and 

 the infrahyoid muscles. 



(b) The ascending cervical branch 

 (v) arises at the point where the inferior 



thyroid turns inwards behind the carotid artery ; it proceeds upwards, close to the 

 phrenic nerve, in the groove between the scalenus anticus and rectus anticus major, 

 giving muscular branches to both, and a few which pass transversely outwards across 

 the neck and communicate with others sent outwards from the vertebral artery. 

 Its terminal ramifications anastomose with branches of the occipital and ascending 

 pharyngeal arteries. To the spinal canal the ascending cervical artery often sends 

 two or three spinal branches, which enter the intervertebral foramina along the 

 cervical nerves, and assist in supplying the bodies of the vertebrae, and the spinal 

 cord and its membranes. 



(c) An inferior laryngeal branch ascends with the recurrent nerve to the back of 

 the larynx, and is distributed feo the muscles and mucous membrane in that situation. 



(d) Tracheal branches ramify over the trachea, and anastomose below with the 

 bronchial arteries. 



(e) One or more cesophageal branches descend upon the oesophagus into the 

 chest, and anastomose with the cesophageal branches of the aorta. 



1 Streckeisen, op. cit., p. 395 ; T. Dwight, "The Relations of the Inferior Thyroid Artery and the 

 Recurrent Laryngeal Nerve," Anatom. Anz., 1886 ; Drobnik, " Ueber das Verhaltniss des Nervus re- 

 currens zur unteren Schilddrusenarterie, " Gazeta lekarska, 1886 ; K.Taguchi, "Die Lage des Nervus re* 

 currens Vagi Bur Arteria thyroidea inferior," Arch. f. Anat., 1889. 



