G08 



DISSECTION OF THE PTERYGOID REGION. 



consists of 

 two layers ; 



muscle 

 nearly sub- 

 cutaneous ; 



lies on the 

 jaw; 



To see 

 surface of 

 temporal 

 muscle. 



To see the 

 insertion. 



Origin of 

 temporal 

 muscle ; 



insertion ; 



relations ; 



process and ramus of the lower jaw, extending from the angle 

 behind to the level of the second molar tooth in front. The 

 superficial fibres are inclined downwards and backwards, and form 

 a layer that can be readily separated from the deeper portion of 

 the muscle, in which the fibres run hearty vertically. 



The lower part of the masse ter is covered only by the integu- 

 ments, with the platysma and fascia ; but the upper is partly con- 

 cealed by the parotid gland, and is crossed by Stenson's duct, and 

 by the transverse facial vessels and branches of the facial nerve. 

 The anterior border projects over the buccinator muscle, and a 

 quantity of loose fat resembling that in the orbit is found beneath 

 it. The muscle covers the ramus of the jaw, and the masseteric 

 nerve and artery entering its deep surface. 



Action. It raises the lower jaw with the internal pterygoid in 

 the mastication of the food. 



Dissection. To lay bare the temporal muscle to its insertion, 

 the following dissection is to be made : The temporal fascia is to 

 be detached from the upper bolder of the zygomatic arch and 

 removed from the surface of the muscle. Next, the arch is to be 

 sawn through in front and behind, so as to include all its length ; 

 and is to be thrown down (without being cut off) with the masseter 

 still attached to it, by separating the fibres of that muscle from the 

 ramus of the jaw. In detaching the masseter, its nerves and vessels, 

 which pass through the sigmoid notch of the lower jaw, will come 

 into view, and should be dissected out of the muscle. 



The surface of the temporal muscle may be then cleaned. And 

 to expose its termination, let the coronoid process be sawn off by a 

 cut passing from the centre of the sigmoid notch to the last molar 

 tooth, so as to include the insertion of the muscle. Before sawing 

 the bone let the student find and separate from the muscle the buccal 

 vessels and nerve issuing from beneath it anteriorly. Lastly, the 

 coronoid process should be raised and the fat removed, in order 

 that the lower fibres of the temporal muscle and their contiguity to 

 the external pterygoid beneath them may be seen. 



The TEMPORAL MUSCLE (fig. 218, x ) arises from the fascia covering 

 it, and from the bones forming the inner wall of the temporal fossa 

 (p. 506), reaching upwards to the semicircular line on the side of 

 the skull, and downwards to the infratemporal crest on the great 

 wing of the sphenoid bone. From this extensive origin the fibres 

 converge to a tendon, which appears on the outer surface of the 

 muscle, and is inserted into the borders and inner surface of the 

 coronoid process, as well as into a groove on the front of the ramus 

 of the lower jaw, extending downwards nearly to the last molar tooth. 



Behind the posterior border of the tendon are the masseteric 

 vessels and nerve, and in front of it the buccal vessels and nerve : the 

 last nerve occasionally perforates some of the fibres of the muscle. 



Action. All the fibres contracting, the muscle will raise the 

 mandible and press it forcibly against the upper jaw. The hinder 

 fibres acting alone can retract the lower jaw after it has been moved 

 forwards by the external pterygoid. 



