I welcome you to this lecture on the “Vertebral
At the conclusion of this lecture, you, as
a learner, should be able to describe the
vertebral segments and the number of vertebrae
in each segment. You should be able to describe
the vertebral curvatures and their formation.
Describe the formation of inner vertebral
foramina and their clinical significance.
Describe the structural blueprint of a typical
Vertebra. Compare and contrast the structural
features of vertebral segments. And then, lastly,
you should be able to describe the vertebral
articulations and ligaments and their functions.
I then will summarize the important take-home
Messages, and then lastly, I’ll provide
attribution for the images that were used
throughout this lecture.
Here is a body map to quickly orient us to
the region of interest. And we’re going
to focus here on the posterior view. And you
see this furrow right down the midline. This
furrow represents the location of structural
elements of our vertebral column. And this
would be the spinous processes. So, we’re
going to be looking right along this area
to define the segmentation of the vertebral
First, let’s take a look at some basic concepts
of the vertebral column and our starting point
is with segmentation.
What we have within the vertebral column are
various segments. We will have a cervical
segment and that is represented by the first
seven vertebrae that we see here in the anterior
view and then we also see the seven vertebrae
posteriorly. The thoracic segment will be
the next twelve vertebrae. And we see the
general location of the thoracic vertebrae
in through here. And then posteriorly, we
are looking in this general region for our
twelve thoracic vertebrae. Just inferior to
the thoracic segment, we have the lumbar region
and we have five lumbar vertebrae and our
starting point here, let’s go with L5, the
fifth lumbar vertebra. So, there is the fifth
one. Above it is 4, 3, 2 and then 1. So, here
we have the five lumbar vertebrae. And then
posteriorly, we start with the last one, 5.
There’s 5, 4, 3, 2, 1.
The next segment is the sacrum. And in the
adult form, the sacrum is formed by a fusion
of five vertebrae. And then lastly, we have
the coccyx, coccygeal vertebrae. Typically,
will number four. However, there is some anatomic
variability. You may have three coccygeal
vertebrae or you may have as many as five.
But, we’re going to stick to the number
four. And so, if we add 7, 12, 5, 5 and 4,
we have 33 vertebrae within the vertebral
The vertebral column also will present two
curvatures - a primary curvature and a secondary
curvature. If we look at primary curvatures,
we were born with these. These will develop
during the foetal period. And there are two
primary curvatures that develop.
The first is the thoracic curvature that we
see in through this area, anterior is to our
left, posterior is to our right in this lateral
view and if you look at it anteriorly, you
will note that the thoracic primary curvature
is concave. The other primary curvature is
the sacral curvature and it too is concave.
And we’ll pause here just for a moment of
reflection. Let me ask a basic question related
to the curvatures, the primary curvatures.
Why would we want to have or wish to have
primary curvatures in the thoracic and sacral
areas that are concave in their appearance?
And the reason that we want to have these
concave primary curvatures is to increase
the volume within the thoracic cavity, to house
our thoracic organs or viscera. Similarly,
in the pelvic area, which is a very narrow
region anatomically, we’ll have a primary
curvature here to house the pelvic viscera.
Secondary curvatures, of which there are cervical
and lumbar secondary curvatures, are going
to develop after birth and they will represent
developmental milestones. So, if we take a
look here in the lateral view of the vertebral
column, we see our cervical secondary curvature,
this level. And if we look anteriorly, we
see that it projects in a convex manner.
Also, the lumbar curvature, which we see here,
has a convexity to it as well. What happens
developmentally when you think about an infant
starting to lift its head, that’s when you’ll
start to develop the cervical secondary curvature.
Then the infant is, a few months later, going
to learn to walk. And when the infant starts
to stand on his or her feet and starts to
walk, the lumbar secondary curvature will
One might also ask how do these curvatures
develop? The primary curvatures are due to
the differences in the height of vertebral
bodies. So, if we take a look here, we’re
looking at a thoracic vertebra. Here’s the
anterior portion of the body and here’s
the posterior portion of the body. You cannot
really perceive it here, but the anterior
height of the vertebral body is a little bit
shorter than the posterior height. Therefore,
these are somewhat wedge-shaped and when you
stack multiple thoracic vertebrae upon one
another, you will then develop this primary
curvature. Same thing happens with the
sacral vertebrae as well.
The secondary curvatures again develop at
developmental milestones and what we have
between the vertebral bodies are intervertebral
discs. And so, when you develop your secondary
curvatures, you’ll have a height difference
between the anterior part of the disc and
the posterior part of the disc such that the
anterior portion will be thicker than its
posterior portion. And then that will confer
the convexity that we see to our secondary
One of the basic functions of the vertebral
column is to protect the spinal cord and the
spinal nerves that issue from the spinal cord.
Once the spinal nerves are formed, they need
a doorway or an exit outwards and that is
mediated by the presence of intervertebral
foramina. And if we take a look, when we stack
our vertebrae upon one another, we will see
these openings or spaces here and these are
the inner vertebral foramina. And the typical
spinal nerve will be transmitted at each of
these particular levels as we move up or as
we move down the vertebral column.
These intervertebral foramina may become stenotic.
And when they become stenotic, they may put
or compress the typical spinal nerve that
leaves the foramen and as a result, neurologic
symptoms can be felt by the individual affected.
As a consequence then, these are loci of clinical