CHAPTER II 



VERTEBRAL COLUMN 







THE human spinal column is made up of some thirty-three segments or vertebra : 

 the length of the column of bones is much increased by intervertebral discs of fibro- 

 cartilage placed between the segments. 



The column has two main functions (a) support of the trunk, etc., and trans- 

 mission of its weight to the pelvis and lower extremities ; (b) protection of the spinal 

 cord and its membranes. The structure of the whole column accords with the necessi- 

 ties of these functions, and thus the vertebra of which it is composed show their indi- 



M.A. 



r.fi 



FIG. 5. A " typical " vertebra (mid-dorsal). From above and from the side. /?. body ; 

 N.A. neural arch; S.F. spinal foramen; Sp. spinous process; T. P. transverse process; 

 L. lamina ; P. pedicle ; Art. articular process. A rib is also indicated in position on one side. 

 E. is the " epiphysial plate " or ring on the body. 



vidual agreement with the general arrangement of the whole : they are modified in 



details according to their position, but they are all built on the same general principle. 



This principle may be followed on a vertebra taken from the centre of the column 



and used as an illustration of the positions of the chief parts of a " typical " vertebra. 



Typical Vertebra (Fig. 5). In front a strong body carries and transmits weight, 

 while the neural arch behind this covers in the spinal cord : in conformity with this 

 we find the strong pads of the intervertebral discs placed between the bodies of con- 

 tiguous vertebrae, whereas the arches are connected by ligaments and tend to overlap 

 one another. 



In the articulated column the successive arches and ligaments, with the backs 

 of the bodies, enclose a neural or spinal canal for the cord and membranes, and the 

 portion of the canal that is enclosed in the neural arch of each separate bone constitutes 

 the spinal foramen of that vertebra. 



The neural arch has spinous and transverse processes projecting from its back 

 and sides respectively, for the attachment of muscles and ligaments : the transverse 

 processes also help to support ribs in their attachment to the column. Each half 6f 

 the neural arch is divided by the position of the transverse process into a posterior 



