Column and Vertebrae
Vertebral Column Sections
Vertebral Column Overview
The Vertebral Column (Spinal Column) supports the
head and encloses the spinal cord.
The spinal column is comprised of 26 individual bones,
these bones are referred to as vertebrae. The spinal column is divided
into 5 different areas containing groups of vertebrae and are grouped
7 cervical vertebrae in the neck.
12 thoracic vertebrae in the upper back corresponding
to each pair of ribs.
5 lumbar vertebrae in the lower back.
5 sacral vertebrae which are fused together
to form 1 bone called the sacrum.
4 coccygeal vertebrae that are fused together
to form the coccyx or tailbone.
The vertebrae are referred to by their name and number,
counting down from the top of the spinal column as follows:
The cervical vertebrae are C1 - C7
The thoracic vertebrae are T1 T12
The lumbar vertebrae are L1 L5
The sacrum and coccyx do not have numbers
and each is thought of as one bone. Spinal nerves exit the sacrum
and coccyx at levels (Foramen) within the main structure of each
General Characteristics of a Vertebra
A typical vertebra consists of two essential
parts, an anterior segment - the body, and a posterior
part - the vertebral or neural arch; these enclose a foramen,
the vertebral foramen. The vertebral arch consists
of a pair of pedicles and a pair of laminae, and supports
seven processes, four articular, two transverse, and
FIG. 1 - A typical thoracic vertebra, viewed
FIG. 2– Sagittal section of a lumbar
When the vertebrae are articulated with each other
the bodies form a strong pillar for the support of the head and
trunk, and the vertebral foramina constitute a canal for the protection
of the medulla spinalis (spinal cord), while between every pair
of vertebrae are two apertures, the intervertebral foramina, one
on either side, for the transmission of the spinal nerves and vessels.
Body (corpus vertebrae): The body
is the largest part of a vertebra, and is more or less cylindrical
in shape. Its upper and lower surfaces are flattened and rough,
and give attachment to the intervertebral fibrocartilages, and each
presents a rim around its circumference. In front, the body is convex
from side to side and concave from above downward. Behind, it is
flat from above downward and slightly concave from side to side.
Its anterior surface presents a few small apertures, for the passage
of nutrient vessels; on the posterior surface is a single large,
irregular aperture, or occasionally more than one, for the exit
of the basi-vertebral veins from the body of the vertebra.
Pedicles (radices arci vertebrae): The pedicles
are two short, thick processes, which project backward, one on either
side, from the upper part of the body, at the junction of its posterior
and lateral surfaces. The concavities above and below the pedicles
are named the vertebral notches; and when the vertebrae are articulated,
the notches of each contiguous pair of bones form the intervertebral
foramina, already referred to.
Laminae: The laminae are two broad plates directed
backward and medial ward from the pedicles. They fuse in the middle
line posteriorly, and so complete the posterior boundary of the
vertebral foramen. Their upper borders and the lower parts of their
anterior surfaces are rough for the attachment of the ligamenta
Processes - Spinous Process (processus spinosus): The
spinous process is directed backward and downward from the junction
of the laminae, and serves for the attachment of muscles and ligaments.
Articular Processes: The articular processes,
two superior and two inferior, spring from the junctions of the
pedicles and laminae. The superior project upward, and their articular
surfaces are directed more or less backward; the inferior project
downward, and their surfaces look more or less forward. The articular
surfaces are coated with hyaline cartilage.
Transverse Processes (processus transversi): The
transverse processes, two in number, project one at either side
from the point where the lamina joins the pedicle, between the superior
and inferior articular processes. They serve for the attachment
of muscles and ligaments.
Structure of a Vertebra (Fig. 2): The body
is composed of cancellous tissue, covered by a thin coating of compact
bone; the latter is perforated by numerous orifices, some of large
size for the passage of vessels; the interior of the bone is traversed
by one or two large canals, for the reception of veins, which converge
toward a single large, irregular aperture, or several small apertures,
at the posterior part of the body. The thin bony lamellae of the
cancellous tissue are more pronounced in lines perpendicular to
the upper and lower surfaces and are developed in response to greater
pressure in this direction (Fig. 2). The arch and processes projecting
from it have thick coverings of compact tissue.