The cervical spine is comprised of seven vertebrae: C1, C2, C3, C4, C5, C6, and C7. These vertebrae begin at the base of the skull and extend down to the thoracic spine. The cervical vertebrae have cylindrical bones that lie in front of the spinal cord and stack up one on top of the other to make one continuous column of bones in the neck.
At each level, the vertebrae protect their segment of the spinal cord and work with muscles, tendons, ligaments, and joints to provide a combination of support, structure, and flexibility to the neck.
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The cervical vertebra nearest the skull, C1, is the smallest, and then the vertebrae get bigger as they go down to C7. The lower vertebrae need to be bigger to support the extra loads from above. Similarly, all of the cervical vertebrae are smaller than the thoracic vertebrae (upper and middle back), and the largest vertebrae are in the lumbar spine, or lower back.
Typical Vertebrae: C3, C4, C5, and C6
Cervical vertebrae C3 through C6 are known as typical vertebrae because they share the same basic characteristics with most of the vertebrae throughout the spine. Typical vertebrae have:
- Vertebral body. This is a cylindrical-shaped, thick part at the front of the bony vertebra. When vertebrae are stacked on top of each other, the disc in between them at each level provides cushioning between the bony vertebrae and helps absorb shocks. The vertebral body handles most of the load for a vertebra.
- Vertebral arch. This bony arch wraps around the spinal cord toward the back and consists of two pedicles and two laminae. The pedicles connect with the vertebral body in the front, and the laminae transition into the spinous process in the back of the vertebra.
- Facet joints. Each vertebra has a pair of facet joints, also known as Zygapophysial joints, or Z joints for short. These joints, located between the pedicle and lamina on each side of the vertebral arch, are lined with smooth cartilage to enable limited movement between two vertebrae. The small ranges of motion between the two vertebrae can add up to significant ranges of motion for the entire cervical spine in terms of rotation, forward/backward, and side bending.
Top Vertebrae: C1 and C2 at the Top of the Neck
C1 and C2 are considered atypical vertebrae and have some distinguishing features compared to the rest of the cervical spine.
- C1 Vertebra (the atlas). The top vertebra, called the atlas, is the only cervical vertebra to not have a vertebral body. Instead, it is shaped more like a ring. The atlas connects to the occipital bone above to support the base of the skull.
This connection is the atlanto-occipital joint. About 50% of the head’s forward/backward range of motion occurs at this joint.
- C2 Vertebra (the axis). The second vertebra, called the axis, has a large bony protrusion (the odontoid process) that points up from its vertebral body, and fits into the ring-shaped atlas above it. The atlas is able to rotate around the axis, forming the atlanto-axial joint.
About 50% of the head’s rotation occurs at this joint.
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Unique Vertebra: C7
The seventh cervical vertebra, also called the vertebra prominens, is considered a unique vertebra and usually has the most prominent spinous process. When feeling the back of the neck, the C7 vertebra’s bony spinous process will stick out more than the other cervical vertebrae.
C7 is the bottom of the cervical spine and connects with the top of the thoracic spine, T1, to form the cervicothoracic junction—also referred to as C7-T1. Not only is C7’s spinous process significantly bigger than those of the vertebrae above, it’s also a different shape to better fit with T1 below.
Due to its larger size and key location at the cervicothoracic junction, several more muscles connect to C7’s spinous process compared to other cervical vertebrae.
Joints of Luschka
The joints of Luschka, also known as uncovertebral joints, are found between vertebral segments from C3 down to C7.
These joints are comprised of two uncinate processes—one rising up from the top of each side of the vertebral body—that fit in indentations in the vertebral body above. The joints of Luschka help with the neck’s forward and backward movements while also limiting the bending to either side.
The joints of Luschka are relatively small compared to the facet joints. Also, unlike the facet joints, the joints of Luschka are not present at birth. Typically, the joints of Luschka develop by age 10.
For the most part, the cervical vertebrae are extremely durable and resistant to injury. Most neck pain relating to the cervical vertebrae is the result of wear and tear, not an injury.