Vertebral column is the basic structure that supports the entire skeletal system.
Human Skeleton is divided into axial and appendicular sections.
The axial skeleton structures include cranium, vertebral column and
associated ribs and sternum. The vertebral column protects the spinal
cord and its meninges. It forms a pillar, which contains 33 segments and
lengthens about 70 cm in male and 60 cm in female. The segments can be
divided into cervical, thoracic, lumbar, sacral and coccygeal segments.
The cervical segment has seven vertebral bones, thoracic twelve,
lumbar five, sacral five and coccygeal four. All are separate bones except
sacrum and coccyx. Both are formed by fusion of separate bones.
The Curvature of the Spine
There are four curvatures in the vertebral column. They are two
primary and two secondary curvatures.
The primary curvatures are the thoracic and sacral. They are
convex posteriorly. The secondary curvatures are convex forwards. The
cervical curvature becomes prominent when the child is able to hold its
head up and sit upright. The lumbar curvature appears by 12-18 months
after the child starts walking
A slight lateral curvature seen in upper thoracic region. It is curved
to the right in right handed person and vice versa.
The vertebrae can be divided into vertebral body and vertebral
arch. The body is cylindrical, large in lumbar region. Vertebral arch has
two pedicles, seven processes, and two laminae. The laminae are vertical,
plate like structures, faces together to form spinous process. The spinous
process projects downwards and is the levers for the muscles. The
articular processes are four in number and bearing an articular facet and
articulate with the adjacent vertebrae. Transverse processes projects
laterally from the junction of pedicle and laminae. In thoracic region they
articulate with ribs.
b) Inter vertebral discs
They are fibro cartilaginous discs and interposed between the
adjacent surfaces of vertebral bodies. They are thicker in lumbar region
than in thoracic. Their peripheral parts are supplied by the adjacent blood
vessels. But the central part is avascular. They receive their nutrients by
diffusion from spongy bone of adjacent vertebrae.
The cervical vertebrae are smaller than lumbar and thoracic
vertebrae. Each type of vertebrae has some unique features.