TEMPORAL AND INFRATEMPORAL REGIONS 271 



membrane of the cheek. It anastomoses with Jthe external 

 maxillary (O.T. facial) artery. 



The Posterior Superior Alveolar Branch, froriv the third part 

 of the internal maxillary artery, descends upon the posterior 

 aspect of the maxilla, and sends branches through the alveolar 

 canals of the maxilla for the supply of the upper molar 

 and prsemolar teeth (Fig. no). Some small twigs go to the 

 gum and others supply the lining membrane of the maxillary 

 sinus. 



Pterygoid and Internal Maxillary Veins. The veins in 

 this region are very numerous, but they cannot be studied 

 satisfactorily in an ordinary dissection. They constitute a 

 dense plexus, termed the pterygoid plexus, around the external 

 pterygoid muscle. Tributaries corresponding to the branches 

 of the internal maxillary artery open into this network, 

 whilst the blood is led away from its posterior part by a short 

 wide trunk, called the internal maxillary vein. This vessel 

 accompanies the first part of the internal maxillary artery 

 into the parotid gland, and joins the posterior facial vein 

 behind the neck of the mandible. 



The pterygoid venous plexus is connected with the 

 cavernous sinus by an emissary vein. It communicates with 

 the inferior ophthalmic vein, through the inferior orbital fissure, 

 and with the anterior facial vein by an anastomosing channel 

 called the deep facial vein which descends across the external 

 surface of the buccinator muscle. 



Articulatio Mandibularis. Before the external pterygoid 

 muscle is thrown anteriorly, the temporo-mandibular joint 

 must be examined. It is a tfrarthrodial joint of the ginglymus 

 type, and its cavity is separated into an upper and a lower 

 part by a discus articularis. In connection with it there are 

 the following ligaments : 



LIGAMENTS PROPER. 



ACCESSORY LIGAMENTS. 



1. Capsule. I. Spheno-mandibular. 



2. Temporo-mandibular. 2. Stylo-mandibular. 



Discus ARTICULARIS. 



The capsule encloses the joint cavity. Above, it, is attached 

 posteriorly, laterally, and medially to the margin of the man- 



