VEETEBKAL COLUMN. 



89 



Superior 

 articular process Boot of the vertebral arch 



Spinous process 



attached, whilst others are articular and assist in uniting the different vertebrae 

 together by means of a, series of movable joints. The roots of the vertebral 

 arches (O.T. pedicles) are the bars of bone which pass from the dorsum of the 

 body of the vertebrae, one on each side, 

 to the points where the articular pro- 

 cesses are united to the arch. Each 



root is compressed from side to side, Fovea costaiis superior 



and has rounded superior and in- Fovea costaiis y$fifciK^k^ Bod y 



ferior borders. Since the vertical 

 breadth of the roots is not as great 

 as the height of the body to which 

 they are attached, it follows that 

 when the vertebrae are placed one 

 above the other a series of intervals 

 is left between the roots of the 

 vertebral arches of the different 

 vertebrae. These spaces, enclosed 

 anteriorly by the bodies of the verte- 

 brae and their intervertebral fibro- 

 cartilages and posteriorly by the 

 coaptation of the articular processes, 

 form a series of holes communicat- 

 ing with the vertebral canal ; they 

 are called the intervertebral foramina, 

 and allow the transmission of spinal 

 nerves and vessels. As each inter- 

 vertebral foramen is bounded above 

 and below by one of the roots of 

 the vertebral arch, the grooved 

 surfaces in correspondence with the 

 upper and lower borders of the roots 

 are called the incisurae vertebrales 

 superior et inferior (upper and lower 

 intervertebral notches). Posteriorly, 

 the two roots of each vertebral arch 

 are united by two somewhat flattened 

 plates of bone the laminae which 

 converge towards the median plane, 

 and become fused with the root of 

 the projecting spinous process. The 

 vertical lengths or heights of the 

 laminae and their sloping arrangement are such, that, when the vertebrae are 

 articulated together, they leave little space between them, thus enclosing fairly 

 completely the vertebral canal, of which they form the posterior wall. The edges 

 and inner surfaces of the laminae are rough for the attachment of the ligaments 

 which bind them together. 



The muscular processes are three in number, viz., two processus transversi 

 one on either side and one central or median, the processus spinosus. The 

 transverse processes project laterally on either side from the arch at the point 

 where the root of the vertebral arch joins the lamina. The spinous process extends 

 backwards in the median plane from the point of fusion of the laminae. The 

 spinous processes display much variety of length and form. 



The articular processes (zygapophyses), four in number, are arranged in pairs 

 one superior, the other inferior ; the former are placed on the upper part of the arch 

 where the roots of the arch (pedicles) and laminae join, the latter on the lower part 

 of the arch in correspondence with the superior. Whilst differing much in the 

 direction of their articular surfaces, the upper have generally a backward tendency, 

 whilst the lower incline forwards. 



Fovea cos- 

 taiis trans- 

 versal is 



Superior articular 

 process 



Root of the 



vertebral arch 



Fovea costaiis 



inferior 



Body 



FIG. 106. FIFTH THORACIC VERTEBKA, (A) as viewed 

 from the right side, (B) as viewed from above. 



