I202 A MANUAL OF ANATOMY 



the inferior maxillary nerve, the otic ganglion, and the chorda 

 tympani nerve. Superior. — ^The masseteric and middle and pos- 

 terior deep temporal nerves. Inferior. — ^The inferior dental and 

 lingual nerves, and the spheno-mandibular ligament. The long 

 buccal nerve, with the anterior deep temporal nerve, makes its 

 appearance between the upper and lower heads, and the internal 

 maxillary artery may sink between them. 



Internal Pterygoid — Origin. — (i) The inner surface of the external 

 pterygoid plate of the sphenoid, and the portion of the tuberosity 

 of the palate bone which forms the lower part of the pterygoid 

 fossa ; and (2) the outer surface of the tuberosity of the palate 

 bone, and the adjacent portion of the tuberosity of the superior 

 maxilla. 



Insertion. — (i) The inner aspect of the angle of the inferior 

 maxilla f and (2) the back part of the inner surface of the ramus, 

 between the angle and the dental foramen. 



Nerve-supply. — ^The internal pterygoid branch of the anterior 

 portion of the inferior maxillary division of the fifth cranial nerve. 



The direction of the muscle is downwards, backwards, and out- 

 wards. 



Action. — (i) To elevate the inferior maxilla ; and (2) to draw it 

 forwards. 



Relations — Superficial. — ^The external pterygoid muscle to a 

 slight extent superiorly, the spheno-mandibular ligament, the 

 internal maxillary and inferior dental vessels, and the inferior 

 dental and lingual nerves. Deep. — ^The tensor palati muscle, and 

 the superior constrictor muscle of the pharynx. 



For a description of the spheno-mandibular ligament, see Index. 



Internal Maxillary Artery. — ^This vessel is the larger of the two 

 terminal branches of the external carotid. It arises from that 

 artery opposite the neck of the inferior maxilla, and within the 

 parotid gland. Its course is at first forwards and inwards behind 

 the neck of the mandible, and superficial to the spheno-mandibular 

 ligament. It then inclines upwards and forwards through the 

 zygomatic fossa, usually passing superficial to the external pterygoid 

 muscle, though in many cases it passes beneath it. Having reached 

 the interval between the two heads of the external pterygoid, it 

 sinks deeply between them, and, passing through the pterygo- 

 maxillary fissure, it enters the spheno-maxillary fossa, where it 

 gives off its terminal branches. In those cases where the artery 

 passes beneath the external pterygoid muscle, it forms a pro- 

 jecting curve between the two heads of the muscle. The course 

 of the vessel is very tortuous in adaptation to the mobility of the 

 surrounding structures. 



Owing to its complexity it is convenient to divide the artery into 

 three parts, namely, first, second, and third. The first, or mandibular, 

 part is situated between the neck of the inferior maxilla and the 

 spheno-mandibular ligament, and its course is horizontally forwards 

 and inwards. It is accompanied by the internal maxillary vein, and 



