Cervical Vertebrae (C1 - C7)

1. Overview

The cervical vertebrae are the seven vertebrae (C1 to C7) that form the uppermost portion of the vertebral column, located in the neck region. These vertebrae support the skull, enable a wide range of head and neck movements, and protect the upper portion of the spinal cord. The cervical spine is highly specialized, particularly the first two vertebrae—atlas (C1) and axis (C2)—which are uniquely structured to allow head rotation and flexion. The cervical region is the most mobile section of the spine.

2. Location

The cervical vertebrae are located at the superior end of the vertebral column:

• Superiorly: C1 (atlas) articulates with the occipital condyles of the skull at the atlanto-occipital joint.

• Inferiorly: C7 articulates with the first thoracic vertebra (T1).

• They form the cervical region of the spine, extending from the base of the skull to the thorax.

3. Structure

Cervical vertebrae have a distinct anatomical structure compared to thoracic and lumbar vertebrae:

• General features of C3–C6:

  • Small, oval-shaped vertebral bodies.

  • Large, triangular vertebral foramen.

  • Bifid (split) spinous processes.

  • Transverse foramina in the transverse processes for vertebral artery passage.

• C1 (Atlas):

  • No vertebral body or spinous process.

  • Composed of anterior and posterior arches with lateral masses.

  • Supports the skull and allows nodding ("yes" motion).

• C2 (Axis):

  • Distinguished by the odontoid process (dens) projecting superiorly.

  • Forms a pivot joint with C1 for rotational movement ("no" motion).

• C7 (Vertebra prominens):

  • Has a long, prominent spinous process easily palpable at the base of the neck.

  • Transverse foramina are small and may not transmit the vertebral artery.

4. Function

The cervical vertebrae serve several mechanical and protective functions:

• Support the skull: Maintain head posture and alignment.

• Enable head and neck motion: Allow flexion, extension, lateral bending, and rotation.

• Protect the spinal cord: Encase the upper spinal cord and the origin of spinal nerves.

• Transmit vertebral arteries: Through the transverse foramina (C1–C6) to supply the brain.

5. Physiological role(s)

Beyond biomechanics, the cervical vertebrae play critical roles in various physiological functions:

• Neurological relay: Serve as passageways for the spinal cord and the origin of cervical spinal nerves (C1–C8), which innervate the neck, diaphragm, upper limbs, and parts of the thorax.

• Blood supply to the brain: Vertebral arteries pass through the transverse foramina to form the basilar artery, which contributes to the Circle of Willis.

• Balance and coordination: Cervical proprioceptors provide feedback to the brain for posture and spatial orientation.

• Respiratory influence: The phrenic nerve (C3–C5) innervates the diaphragm, essential for breathing.

6. Clinical Significance

The cervical vertebrae are commonly involved in injuries and pathologies due to their mobility and proximity to vital structures:

• Whiplash injuries:

  • Hyperflexion-hyperextension trauma can strain cervical soft tissues and ligaments.

• Cervical disc herniation:

  • Common at C5–C6 and C6–C7; may compress spinal nerves causing pain, weakness, or numbness in the upper limb.

• Cervical spondylosis:

  • Degenerative changes in the vertebrae and intervertebral discs, leading to neck stiffness, radiculopathy, or myelopathy.

• Atlantoaxial instability:

  • Excessive movement between C1 and C2, seen in trauma or conditions like rheumatoid arthritis or Down syndrome.

• Vertebral artery dissection:

  • Trauma to the artery passing through the transverse foramina can lead to stroke symptoms.

• Fractures:

  • C1 (Jefferson fracture), C2 (Hangman’s fracture), and C7 fractures are serious injuries often requiring imaging and stabilization.