538 



THE BLOOD-VASCULAR SYSTEM 



2. THE SUPERIOR THYREOID ARTERY 



The superior thyreoid artery [a. thyreoidea superior] (figs. 445, 447) arises 

 from the front of the external carotid a little above the origin of that vessel, and, 

 coursing forward, mediall}^, and then downward, in a tortuous manner, supplies 

 the depressor muscles of the hyoid bone, the larynx, the thyreoid gland, and the 

 lower part of the pharynx. The artery at first runs forward and a little upward, 

 just beneath the greater cornu of the hyoid bone. In this part of its course it 

 lies in the superior carotid triangle, and is quite superficial, being covered only 

 with the integument, fascia, and platj^sma. It next turns downward, and passes 

 beneath the omo-hyoid, sterno-hyoid, and sterno-thyreoid muscles, and ends at 

 the upper part of the thyreoid gland by breaking up into terminal glandular 

 branches. The superior thyreoid vein passes beneath the artery on its way to the 

 internal jugular vein. The superior thyreoid is the artery most commonly 

 divided in cases of suicidal wounds of the throat. 



Branches of the Superior Thyreoid Artery 



The named branches of the superior thyreoid artery are: — ^(1) The hyoid; 

 (2) the sterno-mastoid; (3) the superior laryngeal; (4) the crico-thyreoid; (5) 

 anterior; (6) posterior; and (7) glandular. 



Fig. 447. — Scheme of Left Superior Thyreoid Artery. (Walsham.) 



External maxillary artery 



Lingual artery 



Hyoid branch of lingual :::^^ — ^j^Jl_ C»««|ift 



Hyoid branch of superior .( - jf^^^f^ """iir-i— y 



...... ^^^-^ ^^j 



Superior laryngeal branch- 



Crico-thyreoid branch 



) 



External carotid artery 

 Ascending pharyngeal artery 



Internal carotid artery 



Sterno-mastoid branch 



— Superior thyreoid artery 



Common carotid artery 



Inferior thyreoid artery 



(1) The hyoid [ramus hyoideus] is usually a siuall twig which passes along the lower border 

 of the hyoid l)(>ne, lying on the thyreo-hyoid nienihranc under cover of the thyreo-hyoid and 

 sterno-hyoid muscles. It supplies the infra-hyoid bursa and the thyreo-hyoid muscle, and 

 anastomoses with its fellow of the opi)osite side, and with the hyoid branch of the lingual. 

 When the latter artery is small, the hyoid branch of the superior thyreoid is usually com- 

 paratively large, and vice, rersd. 



\{'2) '['he sterno-mastoid [ramus sternocleidomastoidcus] (fig. 447) courses downward and 

 backward across the carotid slieath, and ent(!ring the sterno-mastoid supplies tlie middle i)ortion 

 of that muscle. It gives off slender twigs to the thyreo-hyoid, sterno-hyoid, and omo-hyoid 

 muscles, and the platysma and integuments covering it. At times the vessel arises directly 

 from the external carotid. It lies usually somewhere in the upper part of the incision for tying 

 the common can^tid above th(i omo-hyoid muscle. 



i'S) The superior laryngeal ja. laryngca sujieriorj (fig. 447) passes medially beneath the 



