48 ANATOMY OF THE HEAD AND NECK. 



DISSECTION VII. 



PTERYGO-MAXILLARY REGION. 



The parts beneath the ramus of the jaw are of difficult dissection ; 

 and the numerous important structures crowded into this space, are 

 only by patience eliminated from their apparent confusion, or pre- 

 served in sufficient integrity to permit their examination. The 

 zygoma having been already divided at its two ends, and, with the 

 masseter, turned downward, the next step is to saw through the 

 inferior maxillary bone below its neck, and again from the last molar 

 tooth to just below its angle ; this fragment, with the temporal muscle 

 attached to the coronoid process, is then to be turned outward, and 

 both in reflecting it, and in sawing it through, the greatest caution is 

 to be observed to divide nothing accidentally upon the inside of the 

 bone, the internal maxillary artery and the inferior dental artery and 

 nerve being in close apposition to it. After this piece of bone has 

 been everted, and a little cellular tissue cleared away, the pterygoid 

 muscles will appear, the external directed toward the condyle of the 

 jaw, and the internal toward its angle. The coronoid process should 

 be examined, to see the extent to which the temporal muscle is 

 attached to its inner surface (p. 26). 



THE EXTERNAL PTERYGOID MUSCLE arises by two heads 

 from the greater wing of the sphenoid bone, below the 

 crest, and from the outer surface of the external pterygoid 

 plate ; its fibres converge to be inserted in front of the neck 

 of the inferior maxilla ; its separation into two heads is not 

 always apparent ; when present, the second head is inserted 

 into the inter-articular nbro-cartilage of the ternporo-max- 

 illary articulation. The internal maxillary artery rests upon 

 this muscle. 



The INTERNAL PTERYGOID MUSCLE arises from the ptery- 

 goid fossa and from the inner surface of the external 

 pterygoid plate, and is inserted into the angle and inner 

 surface of the ramus of the lower jaw; its fibres follow the 

 same direction as those of the masseter muscle externally, 

 and from this fact, as well as from the correspondence of 

 their insertions, it has sometimes been called the internal 

 masseter .muscle. 



ARTICULATION OF THE LOWER JAW. 



In the TEMPORO-MAXILLARY ARTICULATION the condyle 

 of the lower jaw is received into the glenoid fossa of the 

 temporal bone, and is held in place by three ligaments. 



The external lateral ligament is a short, stout band of 



