219
CHAPTER SEVEN
Skeletal System
A Typical Vertebra
Although the vertebrae in different regions of the vertebral
column have special characteristics, they also have fea-
tures in common. A typical vertebra has a drum-shaped
body,
which forms the thick, anterior portion of the bone
(f g. 7.33)
. A longitudinal row of these vertebral bodies sup-
ports the weight of the head and trunk. The intervertebral
discs, which separate adjacent vertebrae, are fastened to the
correspond to the regions in which they occur, as shown in
F gure 7.32. The
thoracic
and
sacral curvatures
are concave
anteriorly and are called primary curves. The
cervical curva-
ture
in the neck and the
lumbar curvature
in the lower back
are convex anteriorly and are called secondary curves. The
cervical curvature develops when a baby begins to hold up
its head, and the lumbar curvature develops when the child
begins to stand.
(b)
(a)
Cervical
curvature
Thoracic
curvature
Lumbar
curvature
Lumbar
vertebrae
Thoracic
vertebrae
Cervical
vertebrae
Sacral
curvature
Vertebra
prominens
Rib facet
Intervertebral
discs
Intervertebral
foramina
Sacrum
Coccyx
FIGURE 7.32
The curved vertebral column consists of many vertebrae separated by intervertebral discs. (
a
) Right lateral view. (
b
) Posterior view.
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