214 



HUMAN ANATOMY. 



Interarticular 

 fibro-cartilage 



Fjg. 246. 



Zygoma, cut surface 



External pterygoid 



Styloid 

 process 



The temporo-mandibular articulation ; the joint 

 opened. 



THE TEMPORO-MANDIBULAR ARTICULATION. 

 This is a compound joint, the elements of which are the socket, the condyle, and 

 the vienisc2iSy an intra-articular disk of fibro-cartilage, dividing the cavity into an 

 upper and a lower part, both being enclosed by one capsular tnembrane. The socket 



includes the glenoid fossa and the articular 

 eminence of the temporal^ bone. The articu- 

 lar coating of the socket, which is continued 

 onto the front of the articular eminence, is 

 not true cartilage (Langer), though resem- 

 bling it to the naked eye. The socket is 

 bounded behind by the fissure of Glaser. 

 The tympanic plate behind it is covered by 

 areolar tissue and a part of the parotid gland, 

 which extend to the back of the head of the 

 jaw and make the socket much narrower and 

 deeper than it seems on the dry bone. The 

 interarticular Jibro- cartilage'^ is oblong trans- 

 versely with rounded angles. It rests more 

 on the front of the condyle than on the top. 

 It is concave both above and below, being 

 moulded on the eminentia articularis and on 

 the condyle. It may be merely one millimetre 

 thick in the middle, and is said to be some- 

 times perforated. The thick posterior border 

 fits into the highest part of the socket. The 

 capsule, lax and weak, is attached to the borders of the articular surfaces and to the 

 edges of the interarticular fibro-cartilage. The external lateral ligameyif^ is a com- 

 paratively strong collection of fibres, strengthening the capsule externally. The 

 fibres run downward and back- 

 ward from the tubercle on the 

 zygoma, at the outer end of the 

 articular eminence, to the outer 

 side of the neck as far as the 

 hind border. The effect of this 

 insertion is to place the trans- 

 verse axis of rotation of the jaw, 

 not in the head of the mandible, 

 but in the neck. The capsule 

 receives at the front and inner 

 side two bands of fibrous tissue 

 continuous with the dura mater, 

 which passes through the fora- 

 men ovale around the third di- 

 vision of the fifth nerve. ^ The 

 spheno-ynandibular ligament, * 

 formerly improperly called the 

 internal lateral, is a weak fibrous 

 structure originally developed 

 around a part of Meckel's car- 

 tilage. It runs from the spine 

 of the sphenoid to the lingula 

 without connection with the 

 joint. The capsule is far too 



loose to hold the jaw firmly in place, hence it is supplemented by the powerful 

 muscles of mastication. One of these, the external pterygoid, is inserted into both 

 the head of the lower jaw and the meniscus, which it draws forward, being incorpo- 



•■^ Fawcett : Journal of Anatomy and Physiologj', vol. xxvii., 1893. 



* Discus articularis. " Lig. temporomandibulare. * Lig. sphenomandibulare. 



Fig. 247. 



External lateral ligament 



Ext. auditory 

 meatus 



Styloid process 



Stylo-mandibu 

 lar ligament 



Stylo-hyoid 

 ligament 



Hyoid bone 



The temporo-mandibular articulation, outer aspect. 



