298 



SYNDESMOLOGY 



The Articular Disk (discus articularis; interarticular fibrocartilage; articular menis- 

 cus} (Fig. 311). The articular disk is a thin, oval plate, placed between the 

 condyle of the mandible and the mandibular fossa. Its upper surface is concavo- 

 convex from before backward, to accommodate itself to the form of the man- 

 dibular fossa and the articular tubercle. Its under surface, in contact with the 

 condyle, is concave. Its circumference is connected to the articular capsule; and in 

 front to the tendon of the Pterygoideus externus. It is thicker at its periphery, 

 especially behind, than at its center. The fibers of which it is composed have a 

 concentric arrangement, more apparent at the circumference than at the center. 

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

 membrane. 





Fia. 310. Articulation of the mandible. Medial aspect. 



FIG. 311. Sagittal section of the articulation of the 

 mandible. 



The Synovial Membranes. 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 mandibular fossa and articular tubercle 

 on to the upper surface of the disk. The lower one passes from the under surface of the disk 

 to the neck of the condyle, being prolonged a little farther downward behind than in front. The 

 articular disk is sometimes perforated in its center, and the two cavities then communicate with 

 each other. 



The Stylomandibular Ligament (ligamentum stylomandibulare) ; stylomaxillary 

 ligament (Fig. 310). The Stylomandibular ligament 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 Pterygoideus internus. This ligament separates the 

 parotid from the submaxillary gland, and from its deep surface some fibers of the 

 Styloglossus take origin. Although classed among the ligaments of the temporo- 

 mandibular joint, it can only be considered as accessory to it. 



The nerves of the temporomandibular joint are derived from the auriculotemporal and masse- 

 teric branches of the mandibular nerve, the arteries from the superficial temporal branch of the 

 external carotid. 



Movements. The movements permitted in this articulation are extensive. Thus, the mandible 

 may be depressed or elevated, or carried forward or backward; a slight amount of side-to-side 

 movement is also permitted. It must be borne in mind that there are two distinct joints in this 

 articulation one between the condyle and the articular disk, and another between the disk and 

 the mandibular fossa. When the mouth is but slightly opened, as during ordinary conversation, 



