a. Vertebral Column (Spine). The vertebral column, or spine, is made up of a
vertical series of bony blocks called vertebrae. These vertebrae are joined together in
such a way as to form a semiflexible rod. The spine is the central support for the trunk,
yet allows trunk movements.
(1) Anatomically and functionally, a typical vertebra (figure 4-4) is
constructed of two major parts:
(a) The vertebral body is a drum-shaped cylindrical mass. Its superior
and inferior surfaces are flat. Its function is primarily weight-bearing.
(b) The neural arch extends posteriorly, arching over and protecting the
spinal cord of the central nervous system. From the neural arch are several processes.
These processes serve as attachment areas for the trunk muscles. They also act as
levers during various trunk motions.
Figure 4-4. A typical vertebra (superior and side views.
(2) The vertebral column has 32-33 vertebrae, one on top of the other.
These vertebrae are arranged in regions. The vertebrae of each region have a
characteristic shape. The regions are as follows:
(a) Cervical (neck) region, with seven cervical vertebrae.
(b) Thoracic (chest) region, with 12 thoracic vertebrae.
(c) Lumbar (low back) region with five lumbar vertebrae.