ARTICULATION OF THE LOWER JAW. 



231 



middle odontoid ligament) may be seen, which passes almost perpendicularly from 

 the apex of the odontoid process to the anterior margin of the foramen magnum, 

 being intimately blended with the deep portion of the anterior occipito-atlantal 

 ligament and upper fasciculus of the transverse ligament of the atlas. 



Actions. The odontoid ligaments serve to limit the extent to which rotation 



The vertical portion of 



ODONTOID LIGAMENTS. 



TO f CAPSULAR LIGAMENT 



ITAL i an(l s y novia i 



(. membrane. 



(CAPSULAR LIGAMEN 



" < and synovial 

 (_ membrane. 



FIG. 156. Occipito-axial and atlanto-axial ligaments. Posterior view, obtained by removing the arches of 

 thu vertebra and the posterior part of the skull. 



of the cranium may be carried ; hence they have received the name of check 

 ligaments. 



In addition to these ligaments, which connect the atlas and axis to the skull, 

 the ligamentum nuchse must be regarded as one of the ligaments by which the 

 spine is connected with the cranium. It is described on a subsequent page. 



Surgical Anatomy. The ligaments which unite the component parts of the vertebrae 

 together are so strong, and these bones are so interlocked by the arrangement of their 

 articulating processes, that dislocation is very uncommon, and, indeed, unless accompanied by 

 fracture, rarely occurs, except in the upper part of the neck. Dislocation of the occiput from 

 the atlas has only been recorded in one or two cases ; but dislocation of the atlas from the axis, 

 with rupture of the transverse ligament, is much more common : it is the mode in which 

 death is produced in many cases of execution by hanging. In the lower part of the neck 

 that is, below the third cervical vertebra dislocation unattended by fracture occasionally takes 

 place. 



V. Articulation of the Lower Jaw (Temporo-mandibular). 



This is a ginglymo-arthrodial joint : the parts entering into its formation on 

 each side are, above, the anterior part of the glenoid cavity of the temporal bone 

 and the eminentia articularis ; and, below, the condyle of the lower jaw. The liga- 

 ments are the following : 



External Lateral. Stylo-mandibular. 



Internal Lateral. Capsular. 



Interarticular Fibro-cartilage. 



The External Lateral Ligament (Fig. 157) is a short, thin, and narrow 

 fasciculus, attached, above, to the outer surface of the zygoma and to the 

 tubercle on its lower border ; below, to the outer surface and posterior border of 

 the neck of the lower jaw. It is broader above than below; its fibres are placed 



