280 



THE ARTICULATIONS, OR JOINTS 



a* 



The Stylomandibular ligament (ligamentum stylomandibulare) (Fig. 230) is a 

 specialized band of the cervical fascia, which extends from near the apex of the 

 styloid process of the temporal bone to the angle and posterior border of the 

 ramus of the mandible, between the Masseter and Internal pterygoid muscles. 

 This ligament separates the parotid from the submaxillary gland, and has 



attached to its inner side part of 

 the fibres of origin of the Stylo- 



Si^PPJH|| glossus muscle. Although usually 



J^H|*^~^ classed among the ligaments of 



?. -. -> '.??. -*^ > ^anaaff"ff*"' i '^MM '"' --V- VA .-* ^-^v^ t ne mandible, it can be considered 



only as an accessory to the articu- 

 lation. 



The capsular ligament (cap- 

 sula articularis*) (Figs. 229 and 

 230) forms a thin and loose cap- 

 sule, passing from the circum- 

 ference of the glenoid cavity and 

 the articular surface immediately 

 in front to the upper margin of 

 the articular disk, and from the 

 lower margin of the articular disk 

 to the neck of the condyle of the 

 mandible. It consists of very 

 thin fibres, and is complete. It 

 -^ ^ forms two joint cavities, distinct 



FIG. 230. Temporomandibular articulation. Internal view. from each Other, and Separated 



by the articular disk. So thin is 



it that it is hardly to be considered as a distinct ligament; it is thickest at the 

 back part, and thinnest on the inner side of the articulation. 1 



The articular meniscus (discus articularis) (Fig. 231) is a thin plate of an oval 

 form, placed horizontally between the condyle of the mandible and the glenoid 

 cavity. Its upper surface is con- 

 cavo-convex from before backward, 

 and a little convex transversely, to 

 accommodate itself to the form of 

 the glenoid cavity. Its under sur- 

 face, where it is in contact with the 

 condyle, is concave. Its circumfer- 

 ence is connected to the capsular 

 ligament, and in front to the tendon 

 of the External pterygoid muscle. 

 It is thicker at its circumference, 

 especially behind, than at its centre. 

 The fibres of which it is composed 

 have a concentric arrangement, more 

 apparent at the circumference than 

 at the centre. Its surfaces are 

 smooth. It divides the joint into two cavities, each of which is furnished with a 

 separate synovial membrane reflected from the capsular ligament. 



Synovial Membranes (Fig. 231). The synovial membranes, two in number, are placed, 

 one above, and the other below, the articular disk. The upper one, the larger and looser of the 

 two, is continued from the margin of the cartilage covering the glenoid cavity and eminentia 



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

 lateral ligament; and it certainly seems as deserving of a separate description as is the external lateral ligament. 



FIG. 231. Vertical section of the temporomandibular 

 'articulation. 



