■tHE INTERNAL MAXILLARY ARTERY 



647 



complex course and the large number of branches given off it is convenient to divide 

 it into three parts. 



I. The first part is much the longest, forms an S-shaped curve, and is in great 

 part in contact with the guttural pouch. It passes upward and forward on the 

 medial surface of the mandible a distance of about an inch (ca. 2-3 cm.), and is 

 related here to the vein, which is ventral. It then turns inward on the ventral 

 surface of the lateral pterygoid muscle and the mandibular nerve, passes between 

 that muscle and the tensor palati, and runs forward to enter the alar foramen. 

 This part gives off the following branches: 



1. The inferior alveolar artery (A. alveolaris mandibulse s. inferior)^ passes 

 downward and forward with the homonymous vein and nerve, being at first between 



Fig. 564. — Left Eye of Hobsb, Deeper Dissection. 

 The outer plate of bone has been removed behind the pterygoid crest to expose the vessels and nerves, a, a. Rem- 

 nants of periorbita; 6, 6, stumps of rectus oculi superior; c, obUquus ocuh inferior; d, rectus oculi inferior; e, rectus 

 ocuU lateralis; e', retractor ocuh; /, rectus ocuh medialis ; g, ff, obhquua ocuh superior; A, eyeball; i, trochlear nerve; 

 /fc, ophthalmic nerve; it', nasal nerve; i", infra trochlear nerve; ft'", ethmoidal nerve; i, optic nerve; m, frontal nerve; 

 n, lacrimal nerve; o, zygomatic nerve; p, nerve to obliquus inferior (from oculomotor); g, maxillary nerve; r, mfra- 

 orbital nerve; s, sphenopalatine nerve; (, great palatine nerve; u, small palatine nerve; v, internal maxillary artery; 

 w, buccinator artery (cut off); i, infraorbital artery; i', malar artery; y, spheno-palatine artery; z, great palatine 

 artery; 2', small palatine artery; 1, Z, stumps of zygomatic arch; S, stump of supraorbital process; 4, facial crest; 

 B, temporal fossa; e, external ophthalmic artery; 7, muscular branch of 6; S, lacrimal arterj' (cut) ; 9, supraorbital 

 artery; JO, anterior deep temporal arterj' ; i i , ethmoidal artery . (After EUenberger-Baum, Top. Anat. d. Pferdes.) 



the lateral and medial pterygoid muscles, then between the latter and the ramus of 

 the mandible. It enters the mandibular foramen, passes downward and forward 

 in the mandibular canal, and terminates at the mental foramen by dividing into 

 mental and incisor branches. The mental branch (A. mentalis) emerges through 

 the mental foramen and anastomoses in the lower lip with the opposite artery and 

 the inferior labial. The incisor branch (Ramus incisivus) continues forward in the 

 bone, supplies twigs to the canine and incisor teeth, and anastomoses with its fellow 

 of the opposite side. Collateral branches are detached to the pterygoid and mylo- 

 hyoid muscles, and within the bone to the teeth, alveolar periosteum, the gums, 

 and the spongy substance of the mandible. 



2. The pterygoid arteries, two or three in number, are distributed to the ptery- 

 goid and tensor and levator palati muscles. 



1 Also known as the inferior dental artery. 



