Vertebral Anatomy: Cervical, Thoracic, Lumbar, Sacral Spine
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Introduction
The vertebral column, also known as the spinal column, is made up of 33 vertebrae when most individuals are born.
Some of these vertebrae fuse together by adulthood leaving a total of 24 vertebrae, 1 sacrum, and 1 coccyx - more on this below!
By definition, the vertebrae are the bones of the spine or backbone that function to protect the spinal cord and support the rest of the body and cranium.
The vertebral column can be divided into 5 different regions - cervical, thoracic, lumbar, sacral, and coccygeal.
This EZmed post will walk you through the vertebral column anatomy, and teach you the important features of each vertebra using labeled diagrams and charts.
Every EZmed post provides you with simple tricks to remember the content, and today you will learn an easy way to remember the number of vertebrae in each region of the spinal column.
Let’s get started!
Vertebral Column
The function of the vertebral column, also known as the spinal column, is to the protect and support the spinal cord and bear the weight of the rest of the body.
Most individuals are born with a total of 33 vertebrae.
They include 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal vertebrae.
By adulthood, the 5 sacral vertebrae fuse together to form a single bone called the sacrum.
Likewise, the 4 coccygeal vertebrae fuse together to form a single bone called the coccyx (tailbone).
Therefore, by adulthood the vertebral column consists of 24 vertebrae (7 cervical, 12 thoracic, 5 lumbar), 1 sacrum, and 1 coccyx.
In other words, 24 of the initial 33 vertebrae are mobile and the other 9 are fused together.
The 24 mobile vertebrae articulate with one another and can be moved. They include the 7 cervical, 12 thoracic, and 5 lumbar vertebrae.
The other 9 vertebrae are fused together and are non-mobile. They include the 5 sacral vertebrae (sacrum) and 4 coccygeal vertebrae (coccyx).
The 24 mobile vertebrae are located in the superior region of the spinal column, and the 9 fused vertebrae are in the inferior portion.
Image: There are 33 vertebrae in the vertebral column, 24 of which are mobile and 9 of which are fused. The mobile vertebrae make up the superior portion of the spinal column and include the 7 cervical, 12 thoracic, and 5 lumbar vertebrae. The fused vertebrae make up the inferior portion of the spinal column and include the 5 sacral and 4 coccyx vertebrae.
Vertebral Regions
The vertebral column can be divided into 5 different regions - cervical, thoracic, lumbar, sacrum, and coccyx.
We will walk through each region of the spinal column starting superiorly and moving inferiorly.
Cervical
There are 7 cervical vertebrae labeled C1-C7.
The cervical vertebrae are located in the neck and help to support the head which weighs approximately 10-12 pounds on average.
Image: There are 7 cervical vertebrae located in the neck labeled C1-C7.
Thoracic
There are 12 thoracic vertebrae labeled T1-T12.
The thoracic vertebrae are located in the mid-upper back, and they hold the rib cage to help support and protect the heart and lungs.
The thoracic vertebrae are less mobile than the cervical and lumbar vertebrae.
Image: There are 12 thoracic vertebrae located in the mid-upper back labeled T1-T12.
Lumbar
There are 5 lumbar vertebrae labeled L1-L5.
The lumbar vertebrae are located in the lower back, and they are larger in size compared to the cervical and thoracic vertebrae as they are required to bear more weight and help support us when lifting heavy items.
Image: There are 5 lumbar vertebrae located in the lower back labeled L1-L5.
Trick to Remember Cervical, Thoracic, Lumbar
As mentioned above, the 7 cervical, 12 thoracic, and 5 lumbar vertebrae have the ability to move.
The number of vertebrae in each of these regions can be remembered using “Breakfast, Lunch, and Dinner”.
For breakfast, remember 7am and this will correlate with the 7 cervical vertebrae.
Lunch is at 12pm/noon which will help you recall the 12 thoracic vertebrae.
For dinner, remember 5pm and this will correlate with the 5 lumbar vertebrae.
Image: Breakfast (7am) = 7 Cervical; Lunch (12pm) = 12 Thoracic; Dinner (5pm) = 5 Lumbar
Sacral
There are 5 sacral vertebrae, labeled S1-S5, and they are fused together by adulthood to form the sacrum.
The sacrum articulates with the ilium (hip bones) to form the pelvis.
Image: There are 5 sacral vertebrae that fuse together by adulthood, labeled S1-S5, to form the sacrum.
Coccyx
There are 4 vertebrae that fuse by adulthood to form the coccyx, also known as the tailbone.
Various ligaments and muscles attach to the coccyx including the gluteus maximus and muscles of the pelvic floor.
Image: There are 4 vertebrae that fuse together by adulthood to form the coccyx.
Intervertebral Discs
There is an intervertebral disc located between each mobile vertebra (cervical, thoracic, lumbar), with the exception of between C1 and C2.
Each intervertebral disc forms a cushion between the vertebral bodies preventing the bones from rubbing together.
Image: Intervertebral discs are located between each mobile vertebra, with the exception of C1 and C2, and they prevent the vertebral bodies from rubbing together.
There are 2 main components of an intervertebral disc - the annulus and the nucleus.
The annulus and nucleus essentially function the opposite of one another.
The annulus is made up of fibers that crisscross and hold the 2 vertebral bodies together, whereas the nucleus is a gel-filled sac that pushes the vertebral bodies away from each other.
Image: Each intervertebral disc is made up of the annulus (crisscrossed fibers that hold 2 vertebral bodies together) and the nucleus (gel-filled sac that pushes the vertebral bodies away from each other).
Sometimes an intervertebral disc can herniate, more commonly known as a herniated disc.
This occurs when the nucleus protrudes through the annulus, and might compress the nearby spinal nerve leading to back pain and/or other neurological symptoms.
Image: An intervertebral disc can herniate in which the nucleus protrudes through the annulus and potentially compresses nearby spinal nerves.
C1 and C2 - Atlas and Axis
Now that we understand intervertebral discs and the different regions that make up the spinal column, let’s discuss the anatomy of the vertebrae.
The overall anatomy of each vertebra is similar, with the exception of C1 and C2 as they have slightly different shapes than the rest.
C1 and C2 are the first 2 vertebrae (superior) in the spinal column and are part of the cervical spine.
C1, also known as the atlas, has more of a ring-shape and is located below the occiput of the skull.
The articular processes of C1 allow us to move our head up and down as if we were saying “yes”.
C2, also known as the axis, has a projection coming off of it called the dens or odontoid process.
The dens provides an articulating pivotal point which allows us to move our head to the right and left as if we were shaking our head “no”.
Image: C1 (atlas) and C2 (dens) are the first 2 vertebrae of the spinal column/cervical spine. C1 is located below the occiput of the skull and C2 has a projection called the dens/odontoid process. C1 and C2 allow us to move our head up/down and left/right.
Vertebral Anatomy
The rest of the vertebrae have similar anatomical features discussed below.
The vertebral body is located anteriorly, and the vertebral arch and processes are located posteriorly.
Vertebral Body
The vertebral body is the weight-bearing portion of each vertebra, and they get larger the further down the spinal column as they must bear more weight.
Vertebral Foramen
Posterior to the vertebral body is the vertebral foramen, a hole in which the spinal cord travels through.
Pedicles
The pedicles make up part of the vertebral arch, and they connect the vertebral body to the transverse processes.
Lamina
The laminae make up the second part of the vertebral arch, and they connect the transverse processes to the spinous process.
Transverse Process
Each vertebra has 2 transverse processes that extend laterally and posteriorly.
Of note, the transverse processes of the thoracic vertebrae are unique in that they articulate with the ribs.
Spinous Process
Each vertebra has a posterior projection called the spinous process.
Superior Articular Process
There are 2 superior articular processes located on either superior side of each vertebra that extend upward.
The 2 superior articular processes function to articulate with the inferior articular processes of the vertebra above it.
Inferior Articular Process
There are 2 inferior articular processes located on either inferior side of each vertebra that extend downward.
The 2 inferior articular processes function to articulate with the superior articular processes of the vertebra below it.
Image: Common anatomical features of each vertebra.
Let’s take a look at a side view of 2 vertebrae, so we can better appreciate how the superior and inferior articular processes come together to form a joint.
The 2 superior articular processes articulate with the 2 inferior articular processes of the vertebra above it.
The 2 inferior articular processes articulate with the 2 superior articular processes of the vertebra below it.
Image: The 2 superior articular processes of one vertebra articulate with the 2 inferior articular processes of the vertebra above it, and vice versa.
Lastly, there is one more anatomical feature that is unique to the cervical vertebrae.
There are 2 foramina, one located on each side of the cervical vertebral body, called the transverse foramina.
The transverse foramen allows for passage of the vertebral artery, vertebral vein, and sympathetic nerves.
Image: The cervical vertebrae have 2 transverse foramina that allow for passage of the vertebral artery, vertebral vein, and sympathetic nerves.
Conclusion
Hopefully this was a good overview of the vertebral column anatomy.
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