Figure 1-17.-Vertebral column: A. Left lateral view of vertebral column; B. Posterior view of vertebral column.

Lumbar.-There are five lumbar vertebrae. Located in the small of the back, these vertebrae are the larger and stronger segments of the vertebral column.

Sacrum.-The sacrum is the triangular bone immediately below the lumbar vertebrae. It is composed of five separate vertebrae that gradually fuse together between 18 and 30 years of age. The sacrum is connected on each side with the hip bone and with the coccyx to form the posterior wall of the pelvis.