Bones of the Vertebral Column
Content Reviewers:Viviana Popa, MD, Scott Caterine, BSc (Hons.), MSc, MB, BCh, BAO (Hons.)
The vertebrae come in different shapes and sizes, and they have unique features depending on their region.
Typical vertebrae have a basic structure in common, consisting of a vertebral body, a vertebral arch, and 7 processes: a spinous process, 2 transverse processes, and 2 superior and 2 inferior articular processes.
As you move down the spine the vertebral bodies become larger, as they bear more weight.
Posterior to the vertebral body, there’s the vertebral arch, which consists of two pedicles and two laminae.
The pedicles are short, thick processes that project posteriorly from the vertebral body to meet the laminae, which are two broad, flat plates of bone, that unite in the midline and complete the vertebral arch.
The space between the walls of the vertebral arch and vertebral body is called the vertebral foramen.
Focusing on the 7 processes of the vertebrae, first we have the spinous process, which extends posteriorly from the midline junction of the laminae and serves as an attachment site for ligaments and muscles.
Next, the left and right transverse processes, they extend posterolaterally from the junctions of the pedicles and laminae, while also serving as important attachment sites for ligaments and muscles.
Finally we have the four articular processes. First there’s the left and right superior articular processes, which project superiorly from the junctions of the pedicles and laminae.
Next are the left and right inferior articular processes, which project inferiorly from the junctions of the pedicles and laminae.
The superior articular processes, inferior articular processes, along with the pedicles, the vertebral bodies, and intervertebral discs between vertebral bodies, go on to create U shaped indentations called the superior and inferior vertebral notch.
So, let’s look at the articulation between two typical vertebrae from a lateral angle. The superior and inferior articular processes of each vertebra allow articulation with adjacent vertebrae via their articular facets.
This allows for different movements of the vertebral bodies in the cervical, thoracic, and lumbar regions.
While still looking from a lateral view, you can also see how the inferior vertebral notch of the vertebra on top aligns with the superior vertebral notch of the vertebra below it to form a canal called the intervertebral foramen, through which spinal nerves pass.
Now, what really makes cervical vertebrae stand out is that they have a foramen transversarium, or transverse foramen, which is an opening on each of the transverse processes.
The superior articular facets are directed slightly supero-posteriorly, meaning the facets face up and back slightly, while the inferior articular facets are directed slightly inferiorly and anteriorly, meaning the facets face down and forward slightly.
This allows adjacent cervical vertebrae to sit nicely upon each other. The main movements the facet joints allow in the cervical region are: free flexion and extension, some lateral flexion, and limited rotation.
So, instead of a body, it has paired lateral masses that serve as a body and sustain the weight of the globe-like cranium just like Atlas of Greek mythology, who bore the weight of the literal world on his shoulders.
The transverse processes of the atlas arise from the lateral masses, so these processes are placed more laterally than those of the inferior vertebrae. This makes the atlas the widest of the cervical vertebrae.
Now, the lateral masses have two superior, concave, kidney-shaped articular surfaces.
The anterior and posterior arches extend between the lateral masses and form a complete ring.
The anterior arch has an anterior tubercle and a facet for the dens, and the posterior arch has a posterior tubercle and a groove for the vertebral artery. On the anterior arch, there’s a tubercle for the transverse ligament.
The dens projects superiorly and articulates with the posterior surface of the anterior arch of the atlas, and it’s held in place by the transverse ligament.
It also has inferior articular processes, and transverse processes similar to the other cervical vertebrae.
Okay. I prominens we’re done articulating the multi-faceted details of the cervical vertebrae for now.
Take a moment to see if you can recall the key structures of the typical and atypical cervical vertebrae.
They are intermediate in size, though they do get bigger further down the vertebral column.
On quick glance, an easy way to identify the thoracic vertebrae is from a posterior lateral view, where they look like a giraffe!
This is compared to the lumbar vertebrae which we will talk about shortly, which look like a moose!
From a superior view, the typical thoracic vertebrae, which are T2 through T11, have a heart-shaped vertebral body, a vertebral foramen that is circular and small, and a pair of transverse processes that are long, strong, and extend posterolaterally. Let's look at a typical thoracic vertebra from a lateral view.
The facets of the superior articular processes are nearly vertical and face posteriorly and slightly laterally, while the facets of the inferior articular processes are also nearly vertical but face anteriorly and slightly medially,