514 THE ARTERIES 



THE INFERIOR THYROID ARTERY 



The inferior thyroid, the largest of the three branches into which the thyroid 

 axis divides, ascends tortuously upwards and inwards in front of the verteliral 

 artery, the recurrent laryngeal nerve, and the longus colli muscle, and l:)eliind the 

 common carotid, and the symj)athetic nerve or its middle cervical ganglion, to the 

 thyroid l>ody, where it anastomoses with the superior thyroid artery and the artery 

 of the opposite side. It gives off the following branches: — (1) Muscular; (2) 

 ascending cervical; (3) oesophageal; (4) tracheal; and (5) inferior laryngeal. 



(1) The muscular branches supply the scalenus anticus, longus colli, sterno- 

 hyoid, sterno-thyroid, and omo-hyoid muscles, and the inferior constrictor muscle 

 of the pharynx. 



(2) The ascending cervical (fig. 329) is given off from the inferior thyroid as 

 that vessel is passing l)cneath the carotid sheath. It ascends lietween the scalenus 

 anticus and the rectus cai»itis anticus major, lying parallel and a little internal to 

 the phrenic nerve and l)t4iind the internal jugular vein. It anastomoses with the 

 vertebral, ascending pharyngeal, and occipital arteries, and su])]4ies the following 

 ])ranches: — (a) Muscular, to the deej) muscles of the neck; {h) spinal, which enter 

 the spinal canal Avith spinal liranches of the vertel^ral artery; and (c) phrenic, to 

 the phrenic nerve. Two veins accompany the ascending cervical artery, and end 

 in the innominate vein. 



(3) The oesophageal branches of the inferior thyroid artery supj^ly the 

 oesophagus, and anastomose with the other arteries supplying that tube. 



(4) The tracheal branches ramify on the trachea, where they anastomose with 

 the tracheal branches of the superior thyroid and bronchial arteries. 



(5) The inferior laryngeal branch passes along the trachea to the back of the 

 cricoid cartilage in company with the recurrent laryngeal nerve. It enters the 

 lar\aix beneath the inferior constrictor. Its further distribution in that organ is 

 described under Larynx. 



THE SUPRASCAPULAR ARTERY 



The suprascapular, or transversalis humeri, passes more or less transversely 

 outwards across the root of the neck, lying first beneath the sterno-mastoid, and 

 then in the sul)clavian triangle behind the clavicle and subclavius muscle. At the 

 external angle of this space it is joined Ijy the suprascapular nerve, sinks beneath 

 the posterior belly of the omo-hyoid, and passes over the ligament bridging the 

 scapular notch, the nerve passing through the notch (fig. 343). It then ramifies 

 in the supraspinous fossa of the scapula, and, winding downwards round the base 

 of the s])ine over the neck of the scapula, enters the infraspinous fossa, and ter- 

 minates by anastomosing with the dorsal scapular and posterior scapular arteries. 

 As it lies under cover of the sterno-mastoid muscle, it crosses the ]ihrenic nerve and 

 the scalenus anticus; and as it courses through the sul)clavian triangle, it is se]"»a- 

 rated by the (>ervical fascia which descends from the omo-hyoid to the first rib, 

 from the subclavian artery and brachial plexus of nerves. If this artery is seen in 

 tying the subclavian it should not be injured, as- it is one of the chief vessels by 

 \\'hi(4i the collateral circulation is carried on after ligature of the subclavian in the 

 third part of its course. At the outer part of the subclavian triangle it is covered 

 by the trapezius, and after passing over the scapular ligament it pierces the supra- 

 spinous fascia and ]iasses beneath the supra-spinatus muscle, and ramifies between 

 it and the bone. In the infraspinous fossa it lies l)etween the infra-spinatus and 

 the bone. The artery is ace(un])anie(l bv two veins. 



The branches of the suprascapular are: — (1) Tlie inferior sterno-mastoid, 

 given off to that nuiscle as the vessel crosses behin<l it; (2) the subelaviculai' to 

 the subclavius nmscle; (3) the nutrient, to the clavicle; (4) the sui)rasternal, 

 which passes over the sternal end of the clavicle to the skin of the upper part of 

 the chest; (5) the acromial, to the arterial rete or plexus on the acromial process, 

 to reach which it pierces the trapezius; (6) the articular, to the aciomio-clavicular 



