Cervical Spine Anatomy
The cervical spine, or your neck, is a complex structure making up the first region of the spinal column, starting immediately below the skull and ending at the first thoracic vertebra. The neck is unique in that it supports the weight of your head (4.5-5kg) and allows a variety of head/neck movement, such as turning your head from side to side, nodding, and looking up and down. The cervical column is comprised of 7 bones (C1 to C7), uniquely shaped to protect the spinal cord that descends from the base of your skull and the spinal nerves or root that exit the spine between each set of bones.
Your neck is like no other part of the vertebral spinal column and enables your head and neck a wide range of motion.
Upper Cervical Spine Enables Wide Ranges of Neck Movement
The upper cervical spine is unlike any other part of the vertebral column. The atlas (C1) and the axis (C2) are part of the spine’s craniovertebral junction (CVJ) – this is where the base of your brain becomes part of the spinal column. Working together, the atlas and axis are primarily responsible for spinal rotation, flexion (bend forward) and extension (bend backward). This is the most mobile section of your entire spine. Roughly 50% of flexion and extension of the neck, similar to nodding your head, occurs here and 50% of rotation also occurs here. Remember, while C1 and C2 allow tremendous ranges of neck movement, they are supporting your head too.
C3-C7 Vertebrae, Cervical Discs, Supporting Structures
If you compare the thoracic (mid back) and lumbar (low back) to the cervical, you will see that the C3-C7 bones are smaller. The vertebral bodies are round shapes. At the back of the vertebral body are bony arches that project outward to form the facet joints and spinous processes. These bony elements naturally create a hollow opening in the centre of the cervical spinal column – a canal that houses and protects the spinal cord.
Another similarity is the cervical intervertebral discs – between each level starting below C2 (axis). The discs are strong, flexible tissues of fibrocartilage. In the middle of each disc is a nucleus pulposus, a gel-like structure surrounded by a tough, protective tyre-like outer layer called the annulus fibrosus.
At vertebral levels of the spine, each disc functions to hold the upper and lower vertebrae together, absorb shock, and allow some movement. The height of the disc creates spaces – nerve passageways called foramen or neuroforamen. Spinal nerve roots branch off the spinal cord, in pairs, and leave the spinal column through the foramen.
Ligaments, tendons, and muscles are soft but strong tissues that help support the cervical spine as well as the entire spinal column by limiting excessive movement.
Cervical spine anatomy illustrated
Cervical Spine is Part of the Central Nervous System
The cervical spinal nerves, sometimes called nerve rootlets, exit the spinal canal through the neuroforamen in pairs – 1 nerve exits on the left side, and 1 on the right. These nerve structures are sometimes numbered to correlate with the level in the cervical spine: C1 through C8.
Each cervical nerve innervates or provides sensation (feeling) and motor function (movement) to both sides of a corresponding part of the upper body. In general, the cervical spinal nerves perform these functions including:
- C1, C2, and C3 provide motor function to the head and neck, as well as sensation from the top of your scalp to the sides of your face.
- C4 enables you to shrug your shoulders and automatically causes the diaphragm to contract when you are breathing. The 4th cervical spine nerve also provides sensation to your neck, shoulders, and parts of your upper arms.
- C5 enables various upper body movements like lifting your shoulders and flexing your biceps and enables feeling toward the tip of the shoulder.
- C6 allows you to move your wrists and flex your biceps and also provides sensation to the inner (thumb) side of your forearms and hand.
- C7 powers the triceps muscle on the back of your upper arms and transmits sensation along the back of the arms, and down to the middle finger.
- C8 allows you to open and close your hands (hand grip) and gives you the ability to feel the outer (pinkie) side of your hands and forearms.
Common Cervical Spine Conditions
Common disc disorders include degenerative disc disease and disc herniation that can cause spinal nerve impingement – sometimes called a “pinched nerve.” This can happen when a disc flattens (loss of disc height) or changes shape – the space for a spinal nerve passing through the neuroforamen is restricted. Nerve compression may cause pain that radiates (travels) from the neck into the upper back and arm(s).
Cervical spinal stenosis is a narrowing of the middle portion of the spinal canal and can lead to compression of the spinal cord.
Cervical trauma represents the most serious of the neck conditions a person may experience. Injury anywhere affecting the cervical spinal column can disrupt nerve communication further down the spinal cord, sometimes resulting in paralysis or even death. Damage (even a bruise) to the C4 nerve, which helps power the diaphragm to make breathing possible, can result in losing the ability to breathe unassisted.
Any of these ‘common’ neck disorders can cause compression of the spinal cord, resulting in cervical myelopathy. The neck is the most common spinal level to develop a myelopathy. Neck pain is a common symptom, although not all patients experience pain.
8 Ways to Help Protect Your Cervical Spine
Understanding the anatomy of your cervical spine and the vital nerves it contains should motivate you to adopt behaviours that help prevent neck injury and slow development of degenerative disorders (e.g. cervical disc herniation).
- Always wear a seatbelt.
- Protect your head and upper neck by wearing a helmet when biking.
- Adjust your computer monitor or screen to eye level; avoid slumping.
- Don’t tuck your phone between your ear and shoulder.
- Sleep using a pillow that supports your neck.
- Periodic neck stretching movements and exercises can help release tension and avoid stiff neck
- Talk with your doctor about your bone health; calcium and/or vitamin D supplements.
- Quit smoking and/or vaping.
Acknowledgements
Written by Joshua M. Ammerman, MD
