Collectively, the vertebral bodies make up the bony building blocks of the spine. The bones are stacked on top of each other and securely attached with a disc in between each one.
The vertebral bodies act as a support column to hold up the spine. This column supports about half of the weight of the body, with the other half supported by the muscles.
Each area of the spine has some differences in the form and function of vertebral bodies and how they are attached to adjacent structures, as follows:
The cervical spine (the neck) has seven vertebral bodies, also called segments. The top two segments are unique:
- The first cervical segment (called the atlas) is a ring that does not have a vertebral body. This vertebra is named C1.
- The second vertebral body (called the axis), acts as a post that the first vertebral ring.
- Like the rest of the spine, the next five vertebral segments (named C3-C7) have three joints at each segment, including one disc in the front and paired facet joints in the back.
Unlike the rest of the spine, the segments in the cervical spine contain openings in each vertebral body for arteries to carry blood to the brain (vertebral artery running through the transverse foramen). The cervical vertebrae also serve an important function in protecting the spinal cord, which travels through a space in the center of the vertebral bones and connects the brain with the rest of the body.
The thoracic spine makes up the upper back and has twelve vertebral bodies, labeled T1 through T12.
These structures have very little motion because they are firmly attached to the ribs and sternum (breastbone). There is little motion in the thoracic spine, so this region has less risk of injury or wear and tear.
Since they are major load bearing structures, vertebral bodies in the upper back are prone to developing compression fractures, particularly in patients with osteoporosis (which weakens the bone). These fractures can lead to chronic back pain and progressive misalignment or deformity of the spine.
Other areas of the upper back can also be a source of pain, it is just less common than in the neck or lower back.
Vertebral Components of the Lumbar Spine
The lumbar spine has five vertebral bodies, labeled L1-L5, that extend from the lower thoracic spine to the sacrum at bottom of the spine. The vertebral bodies of the lower back are the largest of the spine and they bear the majority of the body's weight.
Approximately 50% of flexion (bending forward) occurs at the hips, and 50% occurs at the lumbar spine (lower back).
Each segment of the lumbar spine is comprised of the following structures:
- The thick oval segment of bone in the front of the spinal column is called the vertebral body.
- The vertebral bodies are attached to a bony arch through which all the nerve roots run.
- The vertebral arches are interconnected by paired facet joints, which in combination with the disc, create a three joint complex at each vertebral motion segment. This three-joint complex at each vertebral segment (the facet joint) provides support and allows for motion.
- The facet joints have cartilage on each surface and a capsule around them. The cartilage can degenerate as one ages, and lead to degenerative arthritis.
- The spinous process protrudes from the back of the spine, and these are the ridges that can be felt through the skin along the back of the spine.
Each vertebral segment is made up of two bony vertebrae with a spinal disc in between. The spinal disc is also susceptible to a number of problems and may often be a source of pain, as discussed on the next page.