THE INTERNAL MAXILLARY ARTERY 649 



anterior part of the temporal fossa on the deep face of the temporahs muscle, in 

 which it is chiefly distributed. It gives twigs to the orbital fat and the skin of the 

 frontal region. 



2. The external ophthalmic artery (A. ophthalmica externa) emerges from the 

 anterior opening of the alar canal, and enters the apex of the periorbita. Within 

 this it forms a semicircular bend under the rectus oculi superior, and is continued 

 by the ethmoidal artery. Its branches are as follows : 



(a) The supraorbital artery (A. supraorbitalis) is a small vessel which often 

 arises from the anterior deep temporal or the internal maxillary. It passes along 

 the inner wall of the orbit in company with the nerve of the same name to the supra- 

 orbital foramen, through which it emerges. It is distributed to the orbicularis 

 oculi, the corrugator supercilii, and the skin of the supraorbital region. 



(6) The lacrimal artery (A. lacrimalis) runs upward and forward within the 

 periorbita along the lateral edge of the levator palpebrse superioris to the lacrimal 

 gland, in which it is chiefly distributed. It also sends twigs to the upper eyelid. 



(c) Muscular branches (Rami musculares) supply the orbital muscles, the 

 periorbita, the third eyelid, and the conjunctiva. 



(d) Ciliary branches (Aa. ciliares), two sets of very slender arteries, arise 

 from the ophthalmic direct and from the muscular branches. The anterior ciliary 

 arteries (Aa. ciliares anteriores) pierce the sclera in front of the equator and ramify 

 chiefly in the ciliary body and the iris. The posterior ciliary arteries (Aa. ciliares 

 posteriores) pierce the posterior part of the sclera; most of them ramify in the 

 chorioid coat as the short ciliary arteries, but two of larger size, the long ciliary 

 arteries, run forward, one on each side, between the sclera and chorioid to the 

 periphery of the iris. Here they divide into branches which anastomose and form 

 a circle (Circulus iridis major). From this secondary branches are detached which 

 form a second circle around the pupil (Circulus iridis minor). 



(e) The central artery of the retina (A. centralis retinae) is a small vessel which 

 arises from the ophthalmic or from a posterior ciliary artery. It pierces the optic 

 nerve a short distance behind the sclera, and runs in its center to the lamina cribrosa, 

 where it breaks up in thirty to forty fine branches. These appear in the fundus of 

 the eye at the margin of the optic papilla and radiate in the posterior part of the 

 retina. 



(/) The ethmoidal artery (A. ethmoidalis) is the continuation of the oph- 

 thalmic. It enters the cranial cavity through the ethmoidal foramen, passes 

 inward on the cribriform plate, and divides into meningeal and nasal branches. 

 The former ramify in the anterior part of the dura mater and anastomose with 

 branches of the artery of the corpus callosum. The nasal branch passes through the 

 cribriform plate, gives branches to the mucous membrane of the lateral mass of the 

 ethmoid and the adjacent part of the septum nasi, and runs forward on the dorsal 

 turbinate. 



III. The third part passes forward in the pterygo-palatine fossa, accompanied 

 by branches of the maxillary nerve. On reaching the posterior palatine foramen it 

 is continued by the greater palatine artery. Its branches are as follows : 



(1) The buccinator artery (A. buccinatoria) arises from the ventral aspect of 

 the internal maxillary shortly after its emergence (Fig. 562). It turns around the 

 maxillary tuberosity, accompanied by the buccinator nerve, and under the masseter 

 muscle, enters the cheek, and runs forward in it. It supplies branches to the 

 cheek, the superior buccal glands, and the masseter and pterygoid muscles. Near 

 its origin it gives off a branch to the orbital fat behind the periorbita. 



(2) The infraorbital artery (A. infraorbitalis)i arises from the upper aspect of 

 the internal maxillary a little in front of the preceding vessel. It passes upward 

 and forward to the maxillary foramen, runs in the infraorbital canal in company with 



1 Also termed the superior dental artery. 



