n6 



THORAX 



Root of 

 arch (cut) 

 (O.T. pedicle) 



The posterior longitudinal ligament (O.T. posterior common 

 ligament} is placed on the posterior aspects of the vertebral 

 bodies, and therefore within the vertebral canal. It is firmly 

 connected to the margins of the vertebral bodies and to the 

 intervertebral fibro-cartilages, but is separated from the central 

 parts of the bodies by some loose connective tissue and by a 

 plexus of veins. It is constricted where it covers this venous 

 plexus, but widens out opposite the fibro-cartilages. It there- 

 fore presents a scalloped or 

 denticulated appearance. 



The intervertebral fibro- 

 cartilages are a series of 

 discs of white fibre-car- 

 tilage, thicker anteriorly 

 than posteriorly, which are 

 interposed between the 

 bodies of adjacent vertebrae. 

 The peripheral part of each 

 disc, annulus fibrosus, is 

 tough and fibrous; the 

 central portion, nucleus 

 pulposus, is soft and pulpy. 

 The discs increase the 

 elasticity of the spine, 

 and tend to restore it to 

 its natural curvature after 

 it has been deflected by 

 muscular action. 



The intervertebral 

 fibro - cartilages constitute 

 the main bond of union 



between the bodies of the vertebrae, but, except in old people, 

 they are not directly attached to the bone. A thin layer of en- 

 crusting hyaline cartilage coats the opposing vertebral surfaces. 



Vertical and horizontal sections must be made through two or more of 

 the fibro-cartilages, in order that their structure may be displayed. 



The intertransverse ligaments are feeble bands which pass 

 between the tips of the transverse processes. In the lower 

 part of the thoracic region they are intimately blended with 

 the intertransverse muscles : in* the middle and upper parts 

 of the thoracic region they entirely replace the muscles. 



FIG. 55. Posterior Longitudinal Liga- 

 ment of the Vertebral Column. The 

 vertebral arches have been removed 

 from the vertebrae. 



