THORACIC JOINTS 



'45 



Root of 

 arch (cut) 

 (O.T. pedicle) 



Posterior 



longitudinal 



ligament 



attached to the margins of the vertebral bodies and to the 

 intervertebral fibro-cartilages. The most superficial fibres are 

 the longest, and extend from a given vertebra to the fourth 

 or fifth below it. The deeper fibres have a shorter course, 

 and pass between the borders of two or three adjacent 

 vertebrae. The dissectors cannot fail to notice that the origins 

 of the longus colli muscles are closely connected with the 

 upper part of the thoracic 

 portion of the ligament. 



Li gam en turn Longi- 

 tudinale Posterius. 

 The posterior longitudinal 

 ligament (O.T. posterior 

 common ligament) covers 

 the posterior aspects of 

 the vertebral bodies, and 

 is therefore within the 

 vertebral canal. It is 

 firmly connected to the 

 margins of the vertebral 

 bodies and to the inter- 

 vertebral 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 narrow FIG. 73. Posterior Longitudinal Liga- 

 where it covers the venous 

 plexus, but widens out 

 opposite the fibro- 

 cartilages. It therefore presents a scalloped or denticulated 

 appearance. 



The intervertebral fibro-cartilages are a series of discs of 

 white fibro-cartilage which are interposed between the bodies 

 of adjacent vertebrae. They are thicker posteriorly than 

 anteriorly in the thoracic region. The peripheral part of 

 each disc, the annulus fibrosits, is tough and fibrous ; the 

 central portion, the nucleus pulposus, is soft and pulpy. The 

 discs increase the elasticity of the vertebral column, and tend 

 to restore it to its natural curvature after it has been 

 deflected by muscular action. 



The intervertebral fibro-cartilages constitute the main 



VOL. ii 10 



meat of the Vertebral Column. The 

 vertebral arches have been removed 

 from the vertebrae. 



