THE EXTERNAL CAROTID ARTERY 



591 



The External Carotid Artery (A. Carotis Externa) (Figs. 437, 438). 



The external carotid artery commences opposite the upper border of the thyroid 

 cartilage, and, taking a slightly curved course, passes upward and forward, and 

 then inclines backward to the space between the neck of the condvle of the man- 

 dible and the external meatus, where it divides into the superficial temporal and 

 internal maxillary arteries. It rapidly diminishes in size in its course up the neck, 

 owing to the number and large size of the branches given off from it. In the 

 child it is somewhat smaller than the internal carotid, but in the adult the two 

 vessels are of nearly equal size. At its origin this artery is more superficial and 

 placed nearer the middle line than the internal carotid, and is contained in the 

 triangular space bounded by the Sternomastoid behind, the anterior belly of the 

 Omohyoid below, and the posterior belly of the Digastric and the Stylohyoid 

 above (i. e., the superior carotid triangle). 



Relations. It is covered by the skin, superficial fascia, Platysma, deep fascia, and anterior 

 margin of the Sternomastoid, and is crossed by the hypoglossal nerve, and by the lingual and 

 facial veins; it is afterward crossed by the Digastric and Stylohyoid muscles, and higher up 

 passes deenlv into the substance of the parotid gland, where it lies beneath the facial nerve and 

 the junction of the temporal and internal maxillary veins. Internally is the hyoid bone, wall 

 of the pharynx, the superior laryngeal nerve, and the ramus of the mandible, from which it is 

 separated by a portion of the parotid gland. Externally, in the lower part of its course, is the 

 internal carotid artery. Behind it, near its origin, is the superior laryngeal nerve; and higher up, 

 it is separated from the internal carotid by the Styloglossus and Stylopharyngeus muscles, the 

 glossopharyngeal nerve, and part of the parotid gland. 



PLAN OF THE RELATIONS OF THE EXTERNAL CAROTID. 



In front. 



Skin, superficial fascia. 

 Platysma and deep fascia. 

 Anterior border of Sternomastoid. 

 Hypoglossal nerve. 

 Lingual and facial veins. 

 Digastric and Stylohyoid muscles. 



Parotid gland with facial nerve and temporomaxillary 

 vein in its substance. 



Internally. 



Hyoid bone. 



Pharynx. 



Superior laryngeal nerve. 



Parotid gland. 



Ramus of mandible. 



Externally. 



Internal carotid artery 

 (lower part). 



Behind. 



Superior laryngeal nerve. 

 Styloglossus. 

 Stylopharyngeus. 

 Glossopharyngeal nerve. 

 Parotid gland. 



Surface Marking. The position of the external carotid artery may be marked out with 

 sufficient accuracy by a line drawn from the front of the meatus of the external ear to the side 

 of the cricoid cartilage, slightly arching the median line. 



Applied Anatomy. The application of a ligature to the external carotid may be required 

 in case of wounds of this vessel, or of its branches when these cannot be tied, and in some cases 

 of pulsating tumor of the scalp or face. The operation has not received the attention which it 



