92 DISSECTION OF THE PTERYGOID REGION. 



Articular surfaces of the bones. The lower jaw possesses a thin narrow 

 conclyle, which is elongated transversely, and directed backwards and 

 inwards. 



On the temporal bone is a narrow deep articular hollow (glenoid fossa), 

 which is lengthened from without in, and is placed in front of the Glaserian 

 fissure. In front of this is a prominence of bone (transverse root of the 

 zygomatic process), which is convex from before back and rather hollowed 

 from side to side. 



Movements of the joint. This condyloid articulation is provided with 

 an up and down, a to and fro, and a lateral movement. 



In depressing the jaw, as in opening the mouth, the articular condyle 

 moves forwards till it is placed under the convexity at the fore part of the 

 articular hollow, but the interposed concave fibre-cartilage gives security 

 to the joint. Even with this provision, a slight degree more of sudden 

 motion throws the condyle off the prominence of the temporal bone into 

 the zygomatic fossa, and gives rise to dislocation. 



In this movement the fore and lateral parts of the capsule are made 

 tight ; and the fibre-cartilage is drawn forwards with the condyle by the 

 external pterygoid muscle. 



When the jaw is elevated and the mouth closed, the condyle and the 

 fibro- cartilage glide back into the glenoid fossa. In this position the jaw 

 is placed in the state of greatest security against dislocation. 



The ligaments and the surrounding muscles, which were stretched in 

 the previous movement, are then set at rest. 



During the horizontal motion forwards and backwards the condyle is 

 moved successively to the front and back of the temporal articular surface ; 

 and the lower jaw is slightly depressed, in order that the fore teeth in the 

 upper dental arch should not impede those of the lower. 



By turns the front and back of the capsule will be stretched ; and the 

 fibre-cartilage always follows the condyle of the jaw, even in dislocation. 



Too great motion forwards will be prevented by the coronoid process of 

 the jaw striking against the zygomatic arch; and that backwards, by the 

 meeting of the condyle and the auditory process of the os temporis. 



Lateral horizontal movement puts the jaw first to one side and then to 

 the other. When the jaw is forced to the left side, the right condyle sinks 

 into its articular hollow, whilst the left is projected; and the grinding teeth 

 of the lower dental arch are moved to the left across those of the upper. 

 By the alternate action to opposite sides the food is triturated. 



The inner part of the capsule on the right, and the outer part on the 

 left side, will be put on the stretch when the jaw is carried to the left of 

 the middle line; and the opposite. 



With old edentulous jaws the capsule is much enlarged, and permits the 

 condyle to wander backwards behind the Glaserian fissure. Without this 

 provision the altered lower jaw would not meet the upper to crush the food. 



Dissection. The condyle of the jaw is next to be disarticulated, the 

 external pterygoid muscle being still uncut; and it with the attached mus- 

 cle is to be drawn forwards so as to allow the fifth nerve to be seen. Whilst 

 cutting through the joint capsule, the dissector must be careful of the 

 auriculo-temporal nerve close beneath (fig. 21). 



On drawing forwards the pterygoid muscle, and removing some fat, the 



dissector will find the trunk of the inferior maxillary nerve. All the small 



muscular branches qf the nerve before noted should be traced to the trunk 



in the foramen ovale of the sphenoid bone. The auriculo-temporal branch 



to 



