common ligaments. 129 



Articulations of the Axial Skeleton. 



COMMON VERTEBEAL ARTICULATIONS. 



With the exception of the atlas and dentata, which form 

 special joints, the true Vertebras present great uniformity in 

 their mode of union, articulating with each other by an amphi- 

 arthrosis, which unites their centra, and by a pair of true joints 

 formed by the oblique processes. These connections are com- 

 pleted or strengthened by ligaments, some of which are common, 

 others special, the former are continuous, passing over and 

 uniting many vertebraB, while the latter exist separately between 

 the contiguous segments. 



The bodies are united by intervertebral discs of fibro-cartilage, 

 convex in front, and concave behind, firmly fixed to the articular 

 surfaces of the centra. The discs consist of laminss arranged 

 concentrically, with fibres crossing among themselves, and passing 

 from one articular surface to the other. The central portion is 

 yellowish, presenting more the character of true cartilage, and 

 towards the circumference the laminae become denser. The discs 

 do not exist between the first and second cervical joints ; they 

 are thick in the neck, and thinner in the dorsal region, where 

 they assist in forming sockets for the heads of the ribs. The 

 lumbo-sacral disc is very thick. 



Common Ligaments, 



These are the Superior and Inferior Common, and the Supra- 

 spinous ligaments, the latter in the cervical region being termed 

 the Ligamentum Nuchse. 



The superior common ligament is ribbon-like in form, extend- 

 ing in the spinal canal from the sacrum to the axis, placed upon 

 the superior part of the bodies of the vertebrae, to which, as well 

 as to the intervertebral substances, it is attached, becoming 

 broader at each of the latter attachments. 



The inferior common ligament, situated below the vertebral 

 bodies, stretches from the sacrum only to the sixth dorsal 

 vertebra, anterior to which its place is taken by a. muscle called 

 the longus colli. It is strongest in the posterior part of the 

 dorsal and in the lumbar regions, and broadest ofi the interverte 

 bral substances. 



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