Il8 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. i 89. — The right temporomandibular articulation seen from the outer side ( T ). 

 Fig. 190. — The right temporo-mandibular articulation seen from the inner side ( T ). 

 Fig. 191. — The right temporo-mandibular articulation opened by a sagittal section. The zygomatic 

 arch has been removed (y). 



in the section upon osteology. Considerable quantities of connective tissue are found only in 

 the sphenopetrosal fissure, in the foramen lacerum, and in the petro-occipital fissure (spheno- 

 petrosal and petro-occipital synchondroses). 



THE TEMPOROMANDIBULAR ARTICULATION. 



The temporomandibular articulation (Figs. 189 to 191) is the joint between the condyloid 

 process of the mandible and the mandibular fossa of the temporal bone. It is completely 

 subdivided into an upper and a lower portion by an oblong, biconcave articular disc (Fig. 191), 

 which is adherent to the capsular ligament by its circumference. The two joints which are thus 

 formed, namely, that between the mandible and the disc and that between the disc and 

 the mandibular fossa, act separately. 



The articular capsule of the joint (Fig. 191) is rather thin and relaxed. It embraces the 

 mandibular fossa as far as its posterior non-cartilaginous surface, the articular eminence, and 

 the head of the condyloid process, and is inserted into the neck of the mandible. Its external 

 surface is reinforced by a ligament passing from the zygoma to the neck of the condyloid process, 

 the temporomandibular (external lateral) ligament (Fig. 189), and its fibers pass from above 

 downward and from before backward. 



In the temporomandibular articulation the socket is formed partly by the mandibular fossa and partly by the 

 articular eminence, and over the latter an approximately congruent surface for the head of the condyle is formed by the 

 articular disc. The two temporomandibular articulations act simultaneously. 



When the mouth is opened the head of the condyle with the interarticular disc glides forward upon the articular 

 eminence, and when the mouth is closed it slips back into the mandibular fossa. The opening and closing of the mouth 

 are consequently attended by a sliding of the mandible (a gliding joint). 



In addition to this modified form of hinge movement, the articulation possesses a second kind of motion, the lateral 

 displacement of the mandible in reference to the skull. In this movement one condyloid head remains in the mandibular 

 fossa while the other advances upon the articular eminence, a movement which is impossible when the mouth is opened 

 to its greatest extent. Both the hinge and the lateral movements are combined in the act of mastication. 



INDEPENDENT LIGAMENTS IN THE HEAD. 

 In the vicinity of the temporomaxillary articulation, but without any direct connection 

 with the joint, are situated two ligaments, the sphcnomandibular ligament (Fig. 190) and the 

 stylomandibular ligament (Figs. 191 and 192). The s phenomandibular ligament arises 

 from the under surface of the greater wing of the sphenoid bone near its spine and is 

 inserted into the lingula of the mandible. The stylomandibular ligament takes origin 

 from the styloid process, which is frequently embedded in the ligament for some distance, 

 and passes to the inner surface of the angle of the jaw. Both ligaments are weak and 

 resemble fasciae, *and this is particularly true of the stylomandibular ligament, which radiates 

 directly into the fascia of the internal pterygoid muscle (buccopharyngeal fascia, see page 184). 



