288 



SYNDESMOLOGY 





thicker in the thoracic than in the cervical and lumbar regions, and somewhai; 

 thicker opposite the bodies of the vertebrae than opposite the intervertebral fibro- 

 cartilages. It is attached, above, to the body of the axis, where it is continuous 

 with the anterior atlantoaxial ligament, and extends down as far as the upper 

 part of the front of the sacrum. It consists of dense longitudinal fibers, which 

 are intimately adherent to the intervertebral fibrocartilages and the prominent; 

 margins of the vertebrae, but not to the middle parts of the bodies. In the latter 

 situation the ligament is thick and serves to fill up the concavities on the anterior 

 surfaces, and to make the front of the vertebral column more even. It is composed 

 of several layers of fibers, which vary in length, but are closely interlaced with 

 each other. The most superficial fibers are the longest and extend between four 

 or five vertebrae. A second, subjacent set extends between two or three vertebrae; 

 while a third set, the shortest and deepest, reaches from one vertebra to the next. 

 At the sides of the bodies the ligament consists of 'a few short fibers which pass 

 from one vertebra to the next, separated from the concavities of the vertebral 

 bodies by oval apertures for the passage of vessels. 



FIG. 301. Median sagittal section of two lumbar vertebrae and their ligaments. 



The Posterior Longitudinal Ligament (ligamentum longitudinale postering; posterior 

 common ligament} (Figs. 301, 302). The posterior longitudinal ligament is situated 

 within the. vertebral canal, and extends along the posterior surfaces of the bodies 

 of the vertebrae, from the body of the axis, where it is continuous with the membrana 

 tectoria, to the sacrum. It is broader above than below, and thicker in the thoracic 

 than in the cervical and lumbar regions. In the situation of the intervertebral 

 fibrocartilages and contiguous margins of the vertebrae, where the ligament is more 

 intimately adherent, it is broad, and in the thoracic and lumbar regions presents 

 a series of dentations with intervening concave margins ; but it is narrow and thick 

 over the centers of the bodies, from which it is separated Jby the basivertebral 

 veins. This ligament is composed of smooth, shining, longitudinal fibers, denser 

 and more compact than those of the anterior ligament, and consists of superficial 

 layers occupying the interval between three or four vertebrae, and deeper layers 

 which extend between adjacent vertebras. 



