SUPERIOR THYROID; LINGUAL. 449 



cles ; and distributes numerous branches to the anterior surface of the gland, 

 anastomosing with its fellow of the opposite side, and with the inferior thyroid 

 arteries. Besides the arteries distributed to the muscles and the substance of 

 the gland, the branches of the superior thyroid are the following : 



Hyoid. Superior Laryngeal. 



Superficial descending branch (Sterno-mastoid.) Crico-thyroid. 



The hyoid is a small branch which runs along the lower border of.' the os 

 hyoides, beneath the Thyro-hyoid muscle; after supplying the muscles con- 

 nected to that bone, it forms an arch, by anastomosing with the vessel of the 

 opposite side. 



The superficial descending branch runs downwards and outwards across the 

 sheath of the common carotid artery, and supplies the Sterno-mastoid and 

 neighboring muscles and integument. It is of importance that the situation 

 of this vessel be remembered, in the operation for tying the common carotid 

 artery. There is often a distinct branch from the external carotid distributed 

 to the Sterno-mastoid muscle. 



The superior laryngeal, larger than either of the preceding, accompanies the 

 superior laryngeal nerve, beneath the Thyro-hyoid muscle; it pierces the 

 thyro-hyoid membrane, and supplies the muscles, mucous membrane, and 

 glands of the larynx and epiglottis, anastomosing with the branch from the 

 opposite side. 



The crico-thyroid (inferior laryngeal) is a small branch which runs transversely 

 across the crico-thyroid membrane, communicating with the artery of the op- 

 posite side. The position of this vessel should be remembered, as it may prove 

 the source of troublesome hemorrhage during the operation of laryngotomy. 



Surgical Anatomy The superior thyroid, or some of its branches, are often divided in cases 

 of cut throat, giving rise to considerable hemorrhage. In such cases, the artery should be 

 secured, the wound being enlarged for that purpose, if necessary. The operation may be easily 

 performed, the position of the artery being very superficial, and the only structures of import- 

 ance covering it being a few small veins. The operation of tying the superior thyroid artery, 

 in bronchocele, has been performed in numerous instances with partial or temporary success. 

 When, however, the collateral circulation between this vessel and the artery of the opposite side 

 and the inferior thyroid, is completely re-established, the tumour usually regains its former size. 



The Lingual Artery (Fig. 279) arises from the external carotid between the 

 superior thyroid and facial ; it runs obliquely upwards and inwards to the great 

 cornu of the hyoid bone, then passes horizontally forwards parallel with the 

 great cornu, and, ascending perpendicularly to the under surface of the tongue, 

 turns forwards on its under surface as far as the tip of that organ, under the 

 name of the ranine artery. 



Relations. Its first, or oblique portion, is superficial, being contained in the 

 triangular space already described, resting upon the Middle Constrictor of the 

 pharynx, and covered by the Platysma and fascia of the neck. Its second, or 

 horizontal portion, also lies upon the Middle Constrictor, being covered at first 

 by the tendon of the digastric and the Stylo-hyoid muscle, and afterwards by 

 the Hyo-glossus, the latter muscle separating it from the hypoglossal nerve. 

 Its third, or ascending portion, lies between the Hyo-glossus and Genio-hyo- 

 glossus muscles. The fourth, or terminal part, under the name of the ranine, 

 runs along the under surface of the tongue to its tip ; it is very superficial, 

 being covered only by the mucous membrane, and rests on the Lingualis on 

 the outer side of the Genio-hyo-glossus. The hypoglossal nerve lies nearly 

 parallel with the lingual artery, separated from it, in the second part of its 

 course, by the Hyo-glossus muscle. 



The branches of the lingual artery are, the 



Hyoid. Sublingual. 



Dorsalis Lingua3. Ranine. 



The hyoid branch runs along the upper border of the hyoid bone, supply- 

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