TEMPOR 0-MA XILLA RY AR TICULA TIOX. 



329 



Vertical section of temporo-maxillary ar- 



The Capsular Ligament forms a thin and loose ligamentous capsule, attached 

 above to the circumference of the glenoid cavity and the articular surface im- 

 mediately in front ; below, to the neck of the condyle of the lower jaw. It consists 

 of a few thin scattered fibres, and can hardly be considered as a distinct ligament ; 

 it is thickest at the back part of the articulation. 1 



The Interarticular Fibro-cartilage (Fig. 234) is a thin plate of an oval form, 

 placed horizontally between the condyle of the jaw and the glenoid cavity. Its 

 upper surface is concavo-convex from 

 before backward, and a little convex 

 transversely, to accommodate itself 

 to the form of the glenoid cavity. 

 Its under surface, where it is in con- 

 tact with the condyle. is concave. 

 Its circumference is connected to the 

 capsular ligament, and in front to the 

 tendon of the External pterygoid 

 muscle. It is thicker at its circum- 

 ference, especially behind, than at 

 its centre, where, at times, it is per- 

 forated. The fibres of which it is 

 composed have a concentric arrange- 

 ment, more apparent at the circum- 

 ference than at the centre. Its 

 surfaces are smooth. It divides the joint into two cavities, each of which is fur- 

 nished with a separate synovial membrane. 



The Synovial Membranes, two in number, are placed, one above, and the other 

 below, the fibro-cartilage. The upper one. the larger and looser of the two, is 

 continued from the margin of the cartilage covering the glenoid cavity and 

 eminentia articularis on to the upper surface of the fibro-cartilage. The lower one 

 s from the under surface of the fibro-cartilage to the neck of the condyle of 

 the jaw. being prolonged downward a little farther behind than in front. 



The H'-ri'es of this joint are derived from the auriculo-temporal and masseteric 

 branches of the inferior maxillary. The arteries are derived from the temporal 

 branch of the external carotid. 



Actions. The movements permitted in this articulation are very extensive. 

 Thus, the jaw may be depressed or elevated, or it may be carried forward or 

 backward or from side to side. It is by the alternation of these movements, 

 performed in succession, that a kind of rotatory motion of the lower jaw upon the 

 upper takes place, which materially assists in the mastication of the food. 



If the movement of depression is carried only to a slight extent, the condyles 

 remain in the glenoid cavities, rotating on a transverse axis against the inter- 

 articular fibro-cartilage ; but if the depression is considerable, the condyles glide 

 from the glenoid fossae on to the articular eminences, carrying with them the 

 interarticular fibro-cartilages. so that in opening the mouth widely the two move- 

 ments are combined i. e. the condyle rotates on a transverse axis against the 

 fibro-cartilage. and at the same time glides forward, carrying the fibro-cartilage 

 with it. When the jaw is elevated after forced depression, the condyles and 

 fibro-cartilages return to their original position. When the jaw is carried for- 

 ward and backward or from side to side, an oblique gliding movement of the 

 fibro-cartilages and condyles upon the glenoid cavities takes place in the cor- 

 responding direction. 



The lower jaw is depressed by its own weight, assisted by the Platysma, the 

 Digastric, the Mylo-hyoid. and the Genio-hyoid. It is elevated by the anterior 

 part of the Temporal. Masseter. and Internal pterygoid. It is drawn forward by 



1 Sir G. Humphry describes the internal portion of the capsular ligament separately, as the short 

 internal lateral ligament ; and it certainly seem? as deserving of a separate description as the external 

 lateral ligament is. 



