THE INTERNAL CAROTID ARTERY 549 



Bkanches of the Third Part of the Internal Maxillary Artery 



The branches of the third part of the internal maxillary artery, like those of the first part, 

 all pass through bony canals. They are the following: — (1) The posterior superior alveolar 

 (dental); (2) the infraorbital; (3) the descending palatine; (4) the artery of the pterygoid canal 

 (Vidian); and (5) the sphenopalatine. 



(1) The posterior superior alveolar (dental) artery [a. alveolaris superior posterior] arises 

 from the internal maxillaiy as the latter is passing into the pterygo-palatine (spheno-maxillary; 

 fossa, and descends in a tortuous manner in a groove on the back of the body of the maxilla. 

 It gives off branches to the maxillarj^ sinus, to the molar and premolar teeth, the gums, and to 

 the buccinator muscle. 



(2) The infraorbital artery [a. infraorbitalis] arises from the internal maxillary, generally 

 as a common trunk with the posterior alveolar (dental). It passes forward and a little upward 

 through the pterygo-palatine (spheno-maxillary) fossa; then forward in compan}' with the 

 infraorbital branch of the fifth nerve, first along the groove, and then through the canal in the 

 orbital plate of the maxilla; and finally, emerging on the face at the infraorbital foramen, 

 under cover of the quadratus labii superioris, is distributed to the structures forming the upper 

 lip, the lower eyeUd, the lacrimal sac, and the side of the nose. It anastomoses with the 

 superior labial (coronary) and angular branches of the external maxillary (facial), with the 

 nasal and lacrimal branches of the ophthalmic, and with the transverse facial. It gives off 

 small branches supplying the fat of the orbit and the inferior rectus and inferior oblique muscles. 

 The anterior superior alveolar branch [a. alveolaris superior anterior] passes downward through 

 a groove in the anterior wall of the maxilla, together with the anterior alveolar branch of the 

 infraorbital nerve, and supplies branches to the incisor and canine teeth and the mucous 

 membrane of the maxillary sinus. It has also nasal branches which pass through the foramina 

 in the nasal process of the maxilla. 



(3) The descending palatine artery [a. palatina descendens] descends in the pterygo- 

 palatine canal with the anterior palatine branch of the spheno-palatine ganglion. On emerging 

 on the palate at the greater (posterior) palatine foramen, it divides into the following branches. 

 — (a) The major palatine artery [a. palatina major], which courses forward in the muco-perios- 

 teum at the junction of the hard palate with the alveolar process as far as the incisive (anterior 

 palatine) foramen, where it anastomoses with the spheno-palatine artery; and (6) minor 

 palatine arteries [aa. palatinaj minores], which pass backward and downward into the soft 

 palate, contributing to the supply of that structure, and anastomosing with the ascending 

 palatine artery. After the operation for cleft palate, serious haemorrhage occasionally occurs 

 from the descending palatine artery. The foramen is situated a little behind, and medial ' 

 to, the last molar tooth, and almost immediately in front of the hamular process (fig. 452). 



(4) The arteria canalis pterygoidei or Vidian artery is a long slender branch which passes 

 backward through the pterygoid (Vidian) canal in company with the nerve of the same name 

 into the cartilage of the lacerated foramen. It gives off branches which supply the roof of the 

 pharynx, and anastomose with the ascending pharyngeal and spheno-palatine arteries; also a 

 branch which is distributed to the Eustachian tube; and one which enters the tympanum, and 

 anatomoses with the other tympanic arteries. 



(5) The spheno-palatine [a. sphenopalatina], the terminal branch of the internal maxillary, 

 passes with the naso-palatine branch of the spheno-palatine ganglion from the pterygo-palatine 

 (spheno-maxillary) fossa into the nose through the spheno-palatine foramen. Crossing the 

 roof of the nose in the muco-periosteum, it passes on to the septum, and then runs forward and 

 downward in a groove on the vomer toward the incisive (anterior palatine) foramen, where it 

 anastomoses with the anterior palatine artery, which enters the nose through the lateral com- 

 partment of that foramen (the canal of Stenson). In this course it gives off branches to the roof 

 and contiguous portions of the pharynx, and to the sphenoidal cells. It has also posterior 

 lateral nasal branches [aa. nasales post. laterales], which ramify over the nasal conchas (tur- 

 binate bones) and lateral walls of the nose, and give tw'igs to the ethmoidal and frontal sinuses 

 and the lining membrane of the maxillary sinus; and posterior septal branches [aa. nasales 

 post, septi], which run upward and forward, giving small twigs to the mucous membrane cover- 

 ing the upper part of the septum, and which pass through the cribriform plate of the ethmoid, 

 and anastomose with the ethmoidal arteries (perforating or meningeal branches). 



THE INTERNAL CAROTID ARTERY 



The internal carotid artery [a. carotis interna] (figs. 453 and 454) arises with 

 the external carotid at the bifurcation of the common carotid, opposite the upper 

 border of the thyreoid cartilage, on a level with the fourth cervical vertebra. It 

 is at first placed a little lateral to the external carotid, but as it ascends in the neck 

 the external carotid becomes more superficial and in front of the internal. The 

 internal carotid passes up the neck, in front of the transverse processes of the upper 

 cervical vertebrae, lying upon the longus capitis (rectus capitis ant. major), to the 

 carotid foramen, thence through the carotid canal in the petrous portion of the 

 temporal bone, making at first a forward and medial turn and then a second turn 

 upward, and enters the cranium through the foramen lacerum. It makes a sig- 

 moid curve on the side of the hody of the sphenoid bone, and terminates, after 

 perforating the dura mater, by dividing opposite the anterior clinoid processes 



