THE EXTERNAL CAROTID ARTERY 



593 



the posterior border of the lateral lobe of the gland, the anterior and posterior branches anasto- 

 mose with each other and with branches of the inferior thyroid, and both of them send branches 

 to the thyroid gland (rami glandulares). Beside', the arteries distributed to the muscles by 

 which it is covered and to the substance of the gland, the branches of the superior thyroid are 

 the following: 



Infrahyoid. 

 Sternomastoid. 



Superior Laryngeal. 

 Cricothyroid. 



The infrahyoid branch (ramus hyoideus) is small, and runs along the lower border 

 of the hyoid bone beneath the Thyrohyoid muscle; after supplying the muscles 

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

 opposite side. 



The Sternomastoid branch (ramus sternocleidomastoideus) runs downward and out- 

 ward across the sheath of the common carotid artery, and supplies the Sterno- 

 jnastoid and neighboring muscles and integument. There is frequently a separate 

 branch from the external carotid distributed to the Sternomastoid muscle. 



The superior laryngeal (a. laryngea superior), larger than either of the preceding, 

 accompanies the internal branch of the superior laryngeal nerve, beneath the 

 Thyrohyoid muscle; it pierces the thyrohyoid membrane, and supplies the muscles, 

 mucous membrane, and glands of the larynx, anastomosing with the branch from 

 the opposite side. 



The cricothyroid (ramus cricothyreoideus] is a small branch which runs trans- 

 versely jj 1 cjx3sjj_ < the__cjrict^ communicates with the artery of 

 the opposite side. 



Applied Anatomy. The superior thyroid, or one of its branches, is 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 pur- 

 pose, if necessary. The operation may be easily 

 performed, the position of the artery being very 

 superficial, and the only structures of importance 

 covering it being a few small veins. Thf 



superior 



and inferior thyroid arteries of the involved side are 

 before extirpating a oitrous lobe of the 



The position of the superficial descending branch 

 is of importance in connection with the operation of 

 ligation of the common carotid artery. It crosses 

 and lies on the sheath of this vessel, and may be 

 wounded in opening the sheath. The position of 

 the cricothyroid branch should be remembered, as it 

 may prove the source of troublesome hemorrhage 

 during the operation of laryngotomy. In performing 

 the operation of quick laryngotomy the cricothyroid 

 membrane should be incised transversely in order 

 to avoid this vessel. 



2. The lingual artery (a. lingualis) (Figs. 

 438 and 439) arises from the external carotid 

 between the superior thyroid and facial; it 

 first runs obliquely upward and inward to the 

 great cornu of the hyoid bone; it then curves 



FIG. 440. Showing the relation of the 

 lingual artery and hypoglossal nerve. Leaser's 

 triangle is bounded above by the nerve, below 

 by the posterior belly of the Digastric, and in 

 front by the posterior border of the Mylohyoid, 

 if, , f , i-i indicated by a solid line. The floor of the 



downward and rorward, rorming a loop which triangle is occupied by the Hyogiossus. 

 is crossed by the hypoglossal nerve, and pass- 

 ing beneath the Digastric and Stylohyoid muscles, it runs horizontally forward, 

 beneath the Hyogiossus, and finally, ascending almost perpendicularly to the 

 tongue, turns forward on its under surface as far as the tip, under the name of 

 the ranine artery. 



38 



