482 THE ARTERIES 



the vertebral column, and to the symi)athetic nerve and lymphatic glands. These 

 branches anastomose with branches of the ascending cervical. (2) Tlie pharyngeal 

 supply the superior and middle constrictor muscles and the mucous niemlirane 

 lining them. These vessels anastomose with branches of the sui)erior thyroid. 

 (3) The palatine passes over the upj^er edge of the superior constrictor to the soft 

 palate and its muscles. This branch follows a course similar to that taken by 

 the ascending palatine artery, and when the latter is small may take its place. 

 It generally gives off small twigs to the Eustachian tube and tonsil. (4) The 

 tympanic accompanies the tympanic In-ancli of the glosso-pharyngeal nerve 

 through the tympanic canaliculus into the tympanum, and anastomoses with the 

 other tympanic arteries. (5) The meningeal are distributed to the memljranes 

 of the brain. Some of these pass with the jugular vein through the jugular 

 foramen into the cranium, and supply the dura mater in the posterior fossa of 

 the skull. Others occasionally reach the same fossa through the anterior condy- 

 loid foramen in company with the hypoglossal nerve; while others pass through 

 the cartilage of the middle lacerated foramen and supplv the middle fossa of the 

 skull. 



2. THE SUPERIOR THYROID ARTERY 



The superior thyroid artery arises from the front of the external carotid a 

 little above the origin of that vessel, and, coursing forwards, inwards, and then 

 downwards, in a tortuous manner, supplies the depressor muscles of the hyoid bone, 

 the larynx, the thyroid body, and the lower part of the pharynx. The artery at 

 first runs forwards and a little upwards, just beneath the greater cornu of the 

 hyoid bone. In this part of its course it lies in the sui^erior carotid triangle, and is 

 quite superficial, being covered only with the integument, fascia, and platysma. 

 It next turns downwards, and passes beneath the omo-hyoid, sterno-hyoid. and 

 sterno-thyroid muscles, and ends at the upper i)art of the thyroid body by breaking 

 up into liranches, some of which pass downwards in front, and others behind the 

 lateral lobe of that structure to anastomose with ascending branches from the 

 inferior thyroid; Avhilst others, again, but much smaller in size, pass in the substance 

 of the isthmus across the front of the trachea to anastomose with the superior 

 thyroid artery of the opposite side. These vessels, however, are so small, that if the 

 isthmus is divided accurate^ in the middle line, there is practically no arterial 

 hiemorrhage. From the branch to the thyroid body twigs are given off to the 

 inferior constrictor and the upper part of the oesophagus. These anastomose with 

 branches from the inferior thyroid. The superior thyroid vein passes beneath the 

 artery on its way to the internal jugular vein. The superior thyroid is the artery 

 most commonly divided in cases of suicidal wounds of the throat. 



Branches of the Superior Thyroid Artery 



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



(2) the sterno-mastoid; (3) the superior laryngeal; and (4) the crico-thyroid. 



(1) The hyoid — or infra-hyoid branch as it is sometimes called, usually a 

 small twig — passes along the lower border of the hyoid bone, lying on the thyro- 

 hyoid membrane under cover of the thyro-hyoid and sterno-hyoid muscles. It 

 sup})lies the infra-hyoid l)ursa, and the tliyro-hyoid muscle, and anastomoses with 

 its fellow of the opposite side, an.d with the supra-hyoid liranch of the lingual. 

 When the latter artery is small, the infra-hyoid is usually comparntivfly large, and 

 vice versa. 



(2) The sterno-mastoid (fig. 332) — or middle mastoid artery as it is occa- 

 sionally called — courses downwards and backwards across the carotid sheath, and 

 entering the sterno-mastoid supi)lies the middle portion of that muscle. It gives 

 off slender twigs to the thyro-hyoid, sterno-hyoid, and omo-hy<^id 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 ]iart of the incision for 

 tying the common carotid al)ove the omo-hyoid muscle. 



(3) The superior laryngeal (tig. 329) passes inwards and forwards beneath 



