Anatomy of Skeleton 



Cervical . 



Donal 



while the number of curves gives it a higher resistance to weight than would be afforded 

 by a single curve ; weight is transmitted to the top of the sacrum and from thence to 

 the innominate bones, so that the sacral curve is merely an adaptation to the contents 

 of the pelvis, not concerned in weight-transmission, and differs in the sexes. 



A slight lateral curve is sometimes seen in the line of bodies, concave to the left 

 in the dorsal region and probably due to use of the right arm, with some compensatory 

 deviation above and below. 



The line of the spines shows frequent irregularities without any deviation in the 

 line of the weight-bearing bodies. 



On each side of the line of spines the vertebral groove runs down the length of the 

 column, floored by the laminae and backs of the articular and transverse processes : 

 it is occupied by the deep and intermediate layers of the post-vertebral muscles, the 

 superficial mass lying on these and extending further out. 



Observe the width of the transverse processes. More or less regular in the cervica 1 



region, but great in the first and last members of the 

 series, it decreases from above down in the dorsal 

 vertebras, and increases again in the lumbar to the 

 third or fourth. 



The number of vertebrae permits a considerable 

 amount of movement in the complete column with- 

 out calling for more than a very small amount between 

 the individual segments, thus avoiding the weakening 

 that would result if the segments were fewer and 

 longer. The mechanical stability of the column under 

 all normal movements is assured by making the axis 

 of rotation pass through the bodies and not through 

 the arches, so that the bodies are not displaced from 

 one another in movement. To this end the discs join 

 the bodies together, and the thicker the disc the 

 greater the amount of movement between the bodies. 

 Thus-we find that the discs are thickest in the lumbar 

 and cervical regions, where movement is freest, and 

 shallow in the dorsal series, where naturally the 

 amount of motion is much restricted. 



Where the strong and more flexible lumbar 

 column joins the weaker and more restricted dorsal 

 spine, i.e., about the dorso- lumbar region, is the 

 weakest part of the column surgically. 

 In addition to the discs, the bodies are attached to each other and to the discs 

 by the anterior common ligament, a strong band increasing in width and thickness 

 from above downwards and fastened to the lips of the bodies and the front surfaces 

 of the discs. The posterior common ligament is attached in the same way to the 

 back aspects of the bodies and discs, but is a much weaker and narrower band that 

 decreases in size from above but widens opposite each disc, consequently having a 

 denticulated appearance. 



On the sides of the bodies are other lateral bands or sheets of fibrous tissue, 

 thinner than the anterior ligament, and connected with the attachment of muscles to 

 the column. Thus the whole series of bodies may be said to form a flexible column 

 with the discs, ensheathed in a fibrous covering ; the fibrous sheath does not interfere 

 with movements, being on the discs, but adds to the strength of the whole. 



'Lumbir. 



FIG. 10. Schemes to show the 

 differences between (i) male 

 and (2) female curves. Ob- 

 serve the relatively greater 

 prominence forward of the 

 fourth lumbar segment in the 

 female column. 



