In the thoracic and sacral regions, these curves are oriented concave anterior and each is known as a kyphosis.
A normal spine consists of concave and convex curvatures; however, when the curves become too extreme or the spine begins to curve laterally in the frontal plane, painful spinal conditions may evolve; common abnormal curvatures of the spine include kyphosis, lordosis, and scoliosis. The vertebral column is composed of a series of 31 separate bones known as vertebrae. There are seven cervical or neck vertebrae, 12 thoracic vertebrae, and five lumbar vertebrae. The sacrum is composed of five fused vertebrae, and there are two coccygeal vertebrae which are sometimes fused (fig. 1). In the normal adult there are four curvatures in the vertebral column in an anteroposterior plane. These serve to align the head with a vertical line through the pelvis (fig. 2). In the thoracic and sacral regions, these curves are oriented concave anterior and each is known as a kyphosis. The vertebral column usually consists of 33 vertebrae: 24 presacral vertebrae (7 cervical, 12 thoracic, and 5 lumbar) followed by the sacrum (5 fused sacral vertebrae) and the coccyx (4 frequently fused coccygeal vertebrae). The 24 presacral vertebrae allow movement and hence render the vertebral column flexible. The vertebral column is also known as the spinal column or spine ([link]). It consists of a sequence of vertebrae (singular = vertebra), each of which is separated and united by an intervertebral disc. Together, the vertebrae and intervertebral discs form the vertebral column. The neck (cervical) and low back (lumbar) regions have a slight concave curve, and the thoracic and sacral regions have a gentle convex curve (Fig. 1). The curves work like a coiled spring to absorb shock, maintain balance, and allow range of motion throughout the spinal column.
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what do Normal curves in the vertebral column provide