TEMPO RO -MAXILLARY. 



197 



Temporo-xnaxiUary 



The Capsular Ligament consists of a thin and loose ligamentous capsule, 

 attached above to the circumference of the glenoid cavity and the articular surface 

 immediately 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. 



The Interarticular Jibro-cartilage (fig. 123) is a thin plate of an oval form, 

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

 upper surface is concave from before backwards, and a little convex transversely, 

 to accommodate itself to the form of 

 the glenoid cavity. Its under sur- Fi s- 

 face, where it is in contact with the 

 condyle, is concave. Its circumfer- 

 ence is connected externally to the 

 external lateral ligament, internally 

 to the capsular ligament ; and in front 

 to the tendon of the External ptery- 

 goid muscle. It is thicker at its cir- 

 cumference, especially behind, than 

 at its centre, where it is sometimes 

 perforated. The fibres of which it 

 is composed have a concentric ar- 

 rangement, more apparent at the cir- 

 cumference than at the centre. Its 

 surfaces are smooth, and divide the 

 joint into two cavities, each of which 



is furnished with a separate synovial membrane. When the fibro-cartilage is 

 perforated, the synovial membranes are continuous with one another. 



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 con- 

 tinued from the margin of the cartilage covering the glenoid cavity and eminentia 

 articularis, over the upper surface of the fibro-cartilage. The lower one is inter- 

 posed between the under surface of the fibro-cartilage and the condyle of the jaw, 

 being prolonged downwards a little further behind than in front. 



The Nerves of this joint are derived from the auriculo-temporal, and masseteric 

 branches of the inferior maxillary. 



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

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

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

 performed in succession, that a kind of rotatory movement 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, their anterior part descending only to a slight extent ; 

 but if depression is considerable, the condyles glide from the glenoid fossa3 on to 

 the eminentia articularis, carrying with them the interarticular fibro-cartilages. 

 When this movement is carried to too great an extent, as, for instance, during a 

 convulsive yawn, dislocation of the condyle into the zygomatic fossa occurs ; the 

 interarticular cartilage being carried forwards, and the capsular ligament rup- 

 tured. When the jaw is elevated, the condyles and fibro-cartilages are carried 

 backwards into their original position. When the jaw is carried forwards or 

 backwards, a horizontal gliding movement of the fibro-cartilages and condyles 

 upon the glenoid cavities takes place in the antero-posterior direction ^ whilst in 

 the movement from side to side, this occurs in the lateral direction. 



Y. ARTICULATION OF THE RIBS WITH THE YERTEBRJE. 



The articulation of the ribs with the vertebral column may be divided into two 

 sets. 1. Those which connect the heads of the ribs with the bodies of the verte- 



