372 ARTERIES. 



PLAN OF THE RELATIONS OF THE EXTERNAL CAROTID. 



Infront. Behind. 



Integument, superficial fascia. ^ Superior laryngeal nerve. 



Platysma and deep fascia. f >. Stylo-glossus. 



Hypoglossal nerve. / \ Stylo-pharyngeus. 



Lingual and facial veins. caro'ud! Glosso-pharyngeal nerve. 



Digastric and Stylo-hyoid muscles. V I Parotid gland. 



Facial nerve and parotid gland. \^ / 



Temporal and maxillary veins. ^- -^ 



Internally. 

 Hyoid bone. 

 Pharynx. 

 Parotid gland. 

 Kamus of jaw. 



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

 cases of wounds of this vessel, or of its branches when these cannot be tied ; this, however, is 

 an operation very rarely performed, ligation of the common carotid being preferable, on account 

 of the number of branches given off from the external. To tie this vessel near its origin, below 

 the point where it is crossed by the Digastric, an incision about three inches in length should be 

 made along the margin of the Sterno-mastoid, from the angle of the jaw to the cricoid cartilage, 

 as in the operation for tying the common carotid. To tie the vessel above the Digastric, be- 

 tween it and the parotid gland, an incision should be made from the lobe of the ear to the great 

 cornu of the os hyoides, dividing successively the skin, Platysma. and fascia. By separating 

 the posterior belly of the Digastric and Stylo-hyoid muscles, which are seen at the lower part 

 of the wound, from the parotid gland, the vessel will be exposed, and a ligature may be applied 

 to it. 



Branches. The external carotid artery gives off eight branches, which, for 

 convenience of description, may be divided into four sets. (See Plan of the 

 Branches, fig. 208.) 



Anterior. Posterior. Ascending. Terminal. 



Superior thyroid. Occipital. Ascending pha- Temporal. 



Lingual. Posterior auricular. ryngeal. Internal maxillary. 

 Facial. 



The student is here reminded that many variations are met with in the number, 

 origin, and course of these branches in different subjects ; but the above arrange- 

 ment is that which is found in the great majority of cases. 



The SUPERIOR THYROID ARTERY (figs. 207 and 212) is the first branch given 

 off from the external carotid, being derived from that vessel just below the greater 

 cornu of the hyoid bone. At its commencement, it is quite superficial, being 

 covered by the integument, fascia, and Platysma, and is contained in the trian- 

 gular space bounded by the Sterno-mastoid, Digastric, and Omo-hyoid muscles. 

 After ascending upwards and inwards for a short distance, it curves downwards 

 and forwards in an arched and tortuous manner to the upper part of the thyroid 

 gland, passing beneath the Omo-hyoid, Sterno-hyoid, and Sterno-thyroid muscles ; 

 and distributes numerous branches to its anterior surface, anastomosing with its 

 fellow of the opposite side, and with the inferior thyroid arteries. Besides 'the 

 arteries distributed to the muscles and substance of the gland, its branches are 

 the following : 



Hyoid. Superior laryngeal. 



Superficial descending branch. 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 connected 

 to that bone, it forms an arch, by anastomosing with the vessels 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 neigh- 

 boring muscles and integument. It is of importance that the situation of this 

 vessel be remembered, in the operation for tying the common carotid artery. 



