AR TICULA TIONS. LIGAMENTS. 



425 



TEMPORO-MANDIBULAR ARTICULATION. 



1. Locate and give the synonym for temporo-mandibular articulation. 



This articulation is between the glenoid fossa of the temporal bone and the 

 condyle of the mandible or lower jaw-bone. It is also called temporo-maxillary 

 articulation. 



2. Name some of the conditions that make this articulation one of practical im- 

 portance in medicine and surgery. 



Passing over the part this joint plays in the mastication of food, since this is 

 too well understood by the student to need explanation, we may mention the 

 following : () Temporo-mandibular fixity may occur in cases of exposed tooth- 

 pulp. The nerve supplying the pulp, the trigeminus, also supplies the muscles 

 of mastication. Here, then, we have a moto -sensory reflex circuit. The power- 

 ful contraction of the muscles will cease on the administration of an anaesthetic. 



Interarticular flbro- 



cartilage 



SECTION THROUGH CONOYLE 

 Posterior portion of 

 capsule 



Spheno-mandibul 



Stylo-mandibular ligament 



FIG. 294. VERTICAL SECTION THROUGH THE CONDYLE OF JAW TO SHOW THE Two SYNOVIAL 



SACS AND THE INTERARTICULAR FlBRO-CARTILAGE. 



I once saw a case of fixed jaw produced by a bug in the ear. Here was the 

 same moto-sensory reflex circuit. The same nerve that supplies the muscles of 

 mastication the fifth cranial also supplies the auditory canal through its auriculo- 

 temporal branch. In this case no ordinary traction would open the mouth. An 

 elderly lady suggested the curative property of warm salt-water in "lock-jaw." 

 The ear was filled with water, the bug came out, and instantly the patient could 

 open her mouth, (b) The condyle glides forward onto the eminentia articularis 

 (Fig. 58) when the mouth is open. In this position a dislocation may occur. 

 The condyle is deeply lodged in the glenoid cavity when the mouth is closed. 

 In this position a blow on the chin may fracture the tympanic wall ; while a 

 blow on the angle of the jaw may break the thin dome of the glenoid, and 

 produce injury to the brain. 



3. Hoiv is the glenoid cavity limited in front and beltind / 



Anteriorly, by the eminentia articularis ; posteriorly, by the Glaserian fissure 

 and the post-glenoid tubercle. 

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