There are seven cervical vertebrae in the human neck, labeled C1 through C7. This number is remarkably consistent, not just among humans but across nearly all mammals, from mice to giraffes. These seven bones stack between the base of your skull and the top of your upper back, forming the most flexible section of your entire spine.
What Each Vertebra Does
The seven cervical vertebrae aren’t identical. The top two are highly specialized, and the bottom five (C3 through C7) share a more standard design with a solid body, bony projections, and small joints connecting them to their neighbors.
C1, called the atlas, is a ring-shaped bone that sits right at the base of your skull. It supports the weight of your head, which averages about 10 to 12 pounds. The name comes from the Greek titan Atlas, who held up the sky. C2, called the axis, has a bony peg that fits up into the atlas ring, creating a pivot point. This joint is responsible for the side-to-side rotation when you shake your head “no.” Together, C1 and C2 account for more rotational movement than any other segment of the cervical spine.
C3 through C6 are sometimes called the “typical” cervical vertebrae because they share a common design. They’re smaller and more delicate than vertebrae lower in the spine, and each one has small openings on either side called transverse foramina. These openings create a protected channel for the vertebral arteries that carry blood to the brain. Their spinous processes, the bony bumps you can sometimes feel along the back of your neck, are split into two prongs (bifid), unlike the single-pointed projections found in the rest of the spine.
C7 breaks from this pattern. Known as the vertebra prominens, it has a longer, non-bifid spinous process that sticks straight out from the back of the neck. If you tilt your head forward and run your fingers down the back of your neck, the most noticeable bump at the base is usually C7. Doctors and physical therapists use it as a landmark when examining the spine, though in some people the first thoracic vertebra (T1) is actually more prominent.
Range of Motion in the Cervical Spine
Your cervical spine is the most mobile region of your backbone. In healthy young adults, the neck allows roughly 58 degrees of forward flexion, 59 degrees of extension (looking up), about 42 degrees of side bending in each direction, and around 70 to 71 degrees of rotation to each side. That rotation isn’t spread evenly across all seven vertebrae. The C1-C2 joint alone contributes the largest share of turning motion, while the greatest flexion and extension movements happen between C5 and C6. Lateral bending peaks between C4 and C5.
This means different parts of your neck are doing different jobs during different movements, which also helps explain why certain levels are more vulnerable to wear and injury than others.
Where Problems Are Most Likely
Because the C5-C6 and C6-C7 segments handle the most bending and absorb a large share of mechanical stress, they’re the levels most prone to disc herniation and degenerative changes. Studies across populations in North America, Europe, and Asia consistently find C5-C6 and C6-C7 as the most frequently affected levels when disc problems require surgery. C5-C6 alone accounts for roughly 35% of operated disc herniations in some studies, with C6-C7 not far behind.
These are also the levels that send nerves into your arms and hands, which is why a cervical disc problem often shows up as pain, tingling, or weakness radiating down one arm rather than just neck pain alone.
Anatomical Variations
While the number seven is nearly universal, a small percentage of people have an extra structure called a cervical rib. This is a small, supernumerary rib that grows from C7, present in about 1% of the general population. Most people who have one never know it. In rare cases, a cervical rib can compress nerves or blood vessels passing into the arm, a condition called thoracic outlet syndrome. Among patients diagnosed with that syndrome, cervical ribs show up in nearly 30% of cases, suggesting a strong association even though the rib itself is usually harmless. More than half the time, the extra rib appears on only one side.
Outside of cervical ribs, having more or fewer than seven cervical vertebrae is exceedingly rare in humans and is typically associated with congenital skeletal conditions rather than normal variation.