Viewed laterally the vertebral column
presents several curves, which correspond to the different
regions of the column, and are called cervical, thoracic,
lumbar, and pelvic.
The cervical curve,
convex forward, begins at the apex of the odontoid
(tooth-like) process, and ends at the middle of
the second thoracic vertebra; it is the least marked
of all the curves. The
thoracic curve, concave forward,
begins at the middle of the second and ends at the
middle of the twelfth thoracic vertebra. Its most
prominent point behind corresponds to the spinous
process of the seventh thoracic vertebra. This curve
is known as a kyphotic curve.
lumbar curve is more
marked in the female than in the male;
it begins at the middle of the last
thoracic vertebra, and ends at the
sacrovertebral angle. It is convex
anteriorly, the convexity of the lower
three vertebrae being much greater
than that of the upper two. This curve
is described as a lordotic curve.
The pelvic curve begins
at the sacrovertebral articulation, and ends at
the point of the coccyx; its concavity is directed
downward and forward.
The thoracic and pelvic curves are termed primary
curves, because they alone are present during fetal life.
In the early embryo, the vertebral column is C-shaped, and the cervical
and lumbar curvatures are not yet present in a newborn infant. The cervical
and lumbar curves are compensatory or secondary, and are developed after
birth, the former when the child is able to hold up its head (at three
or four months), and to sit upright (at nine months), the latter at twelve
or eighteen months, when the child begins to walk.
The thoracic portion of the vertebral column also has a slight
lateral curvature, the convexity of which is directed toward
the right side.
This may be produced by muscular action, most persons using the right
arm in preference to the left, especially in making long-continued efforts,
when the body is curved to the right side. In support of this explanation
it has been found that in one or two individuals who were left-handed,
the convexity was to the left side. This curvature is regarded by others
as being produced by the aortic arch and upper part of the descending
thoracic aorta – a view which is supported by the fact that in
cases of situs inversus where the viscera are transposed and the aorta
is on the right side, the convexity of the curve is directed to the left
regions (curvatures) of the vertebral column
and names of individual vertebrae.
The vertebral column seen from