LIGAMENTS OF THE VEETEBEAL COLUMN. 



307 



the fibro-cartilages are thinnest on their anterior aspects in correspondence with 

 the anterior concavity of this section of the vertebral column. 



Each fibro-cartilage consists of a circumferential portion, annulus fibrosus, formed 

 for the most part of oblique parallel fibres running from one vertebra to the 

 other; horizontal fibres are also found. The axial or central part of the fibro- 

 cartilage, the nucleus pulposus, is elastic, soft, and pulpy. 



The superior and inferior surfaces of the fibro -cartilage are closely adherent 

 to the adjoining epiphyseal plates of the vertebral bodies, and as ossification 

 advances, the distinction between epiphyseal plates and vertebral body disappears. 



As a rule the transverse diameter of the fibro-cartilage corresponds to that of 

 the vertebral bodies which it joins together; but in the cervical region, where 

 the inferior margin of the super-imposed vertebra is overlapped on each side by 

 the one which bears it, the fibro-cartilage does not extend to the extreme lateral 

 margin, and in this position a small diarthrosis may be seen at each lateral margin 

 of the fibro-cartilage. 



Lig. Longitudinale Anterius. The anterior longitudinal ligament (O.T. 

 anterior common ligament) (Fig. 293) consists of a wide stratum of longitudinal 

 fibres which extends from the front of the epistropheus vertebra to the front of 

 the superior segment of the sacrum, and becomes gradually wider from above 

 downwards. It lies on the anterior surfaces of the intervertebral fibro-cartilages, to 

 which it is firmly attached as it passes from one vertebra to the other. Its fibres 

 vary in length. Some are attached to contiguous margins of two adjoining 

 vertebrae ; others pass in front of one vertebra to be attached to the next below, 

 and yet others find their lower attachment three or four vertebrae below the one 

 from which they started. None of the fibres are attached to the transverse 

 depression on the anterior surface of a vertebral body. 



Lig. Longitudinale Posterius. The posterior longitudinal ligament (O.T, 

 posterior common ligament) (Fig. 294) is found within the vertebral canal upon 

 the posterior aspect of the vertebral bodies. It 

 consists of longitudinal fibres, and it extends from 

 the sacrum to the epistropheus vertebra, superior 

 to which it is continued to the skull as the 

 mernbrana tectoria. Opposite each interverte- 

 bral fibro-cartilage it is attached to the entire 

 width of the adjacent margins of the two vertebral 

 bodies, its fibres being continued over the posterior 

 surface of the fibro-cartilage. In the lumbar and 

 thoracic regions the width of the ligament is con- 

 siderably reduced opposite the back of each vertebral 

 body, and thus it forms a series of dentate pro- 

 jections along both of its margins ; but in the 

 cervical region the width of the ligament is more 

 uniform. One or two large thin -walled veins 

 escape from the body of each vertebra under cover 

 of this ligament. 



Articulations between Vertebral Arches. 

 The vertebral arch of each typical vertebra carries 

 two pairs of articular processes, by means of which 

 it articulates with adjacent vertebral arches. The 

 articulations between these processes are true 

 diarthroses of the arthrodial variety. 



The distinctive characters of these articular surfaces, as regards their shape 

 j and direction in the different groups of vertebrae, have been referred to in the 

 section on osteology. 



All these articulations are provided with complete but very thin-walled cap- 

 ; sulae articulares, which are thinnest and loosest in the cervical region, where also 

 the movements are freest. Each capsule is lined with a stratum synoviale. 



Associated with these joints between vertebral arches are certain ligaments* which 

 are accessory to the articulations, although they are quite distinct from the capsule. 



FIG. 294. POSTERIOR LONGITUDINAL 

 LIGAMENT OF THE VERTEBRAL COLUMN- 



