THE FRAMEWORK OF THE BODY 



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brae, each bearing a pair of movable ribs; then the lower trunk or lumbar 

 region with 5 large lumbar vertebrae; then the pelvic region with 5 verte- 

 brae tightly fused into a sacrum, which is rigidly attached to the pelvic 

 girdle ; and finally comes the coccyx or bony remnants of the tail, consist- 

 ing of 3, 4, or 5 small vestigial vertebrae. 



neural spine 



Fig. 3.4. Some details of vertebrae and ribs. A, diagram of rib movement in breathing. B, 

 articulation of ribs, showing the two pivot points (p). C, a lumbar vertebra from above. D, 

 the same vertebra from the left side. 



Seen from the front or rear the vertebral column forms a straight line, 

 but in side view it is curved. Its curvatures give the spine spring and 

 resilience in walking and jumping and enable it to absorb more completely 

 the shocks produced by these and other body movements. The tilt of the 

 sacrum brings the weight of the body directly over the legs and, with the 

 lumbar curvature, makes possible the fully erect posture characteristic 

 of man. 



The walls of the thoracic cavity (which encloses the heart and lungs) 

 are supported by the ribs, together with the thoracic vertebrae, the 



