The cervical spine is the uppermost section of the vertebral column, consisting of seven vertebrae labeled C1 to C7. It is the most flexible part of the spine, allowing for a wide range of head and neck movements. The first two vertebrae, the atlas (C1) and axis (C2), are uniquely structured to support the skull and enable rotational movements. The cervical spine also protects the spinal cord as it transitions from the brainstem to the thoracic region.
Location
The cervical spine is located in the neck region, connecting the base of the skull to the thoracic spine. It extends from the occipital bone of the skull to the upper part of the back.
Structure and Anatomy
Vertebral Composition
The cervical spine consists of seven vertebrae, labeled C1 to C7. These vertebrae are the smallest and most mobile in the vertebral column, supporting the head and neck’s flexibility.
- C1 (Atlas): A ring-like structure without a vertebral body, designed to support the skull and facilitate nodding motions.
- C2 (Axis): Features the dens (odontoid process), a peg-like structure that allows rotational movement of the head.
- C3 to C7: Typical cervical vertebrae with small bodies, transverse foramina, and bifid spinous processes (except C7, which often has a non-bifid spinous process).
Vertebral Body
The vertebral body of cervical vertebrae is small and oval-shaped, designed to support the head’s weight while allowing flexibility.
Vertebral Foramen
The vertebral foramen in the cervical spine is large and triangular, providing ample space to protect the spinal cord as it passes through this region.
Processes
The cervical vertebrae have several bony projections:
- Spinous Processes: Short and often bifid (split into two prongs) in vertebrae C2 to C6, providing attachment points for muscles and ligaments.
- Transverse Processes: Contain transverse foramina, which house the vertebral arteries and veins that supply blood to the brain.
- Articular Processes: Superior and inferior processes form facet joints, allowing controlled movement between vertebrae.
Transverse Foramina
A unique feature of the cervical vertebrae is the presence of transverse foramina within the transverse processes. These foramina provide a passageway for the vertebral arteries, veins, and sympathetic nerves.
Intervertebral Discs
Intervertebral discs separate the vertebrae from C2 to C7, consisting of:
- Annulus Fibrosus: The tough, outer ring providing structural stability.
- Nucleus Pulposus: The gel-like inner core that acts as a shock absorber.
C1 and C2 do not have an intervertebral disc between them.
Facet Joints
The cervical spine features synovial facet joints, formed by the articulation of the superior and inferior articular processes of adjacent vertebrae. These joints allow for the spine’s wide range of motion.
Uncovertebral Joints
Located between the uncinate processes (small projections on the lateral edges of vertebral bodies) of C3 to C7, these joints stabilize the cervical spine and prevent excessive lateral motion.
Curvature
The cervical spine exhibits a natural lordotic curve, with a slight forward convexity that helps absorb shock and maintain balance.
Ligaments
The cervical spine is stabilized by several important ligaments:
- Anterior Longitudinal Ligament: Runs along the anterior vertebral bodies, preventing hyperextension.
- Posterior Longitudinal Ligament: Located along the posterior vertebral bodies, limiting hyperflexion.
- Ligamentum Flavum: Connects the laminae of adjacent vertebrae.
- Nuchal Ligament: A strong, midline ligament that extends from the external occipital protuberance to C7, supporting the head and neck.
Spinal Nerves and Intervertebral Foramina
The cervical spine contains openings called intervertebral foramina, formed between adjacent vertebrae. These allow the cervical spinal nerves to exit and innervate the neck, shoulders, and upper limbs.
Function
Support of the Head
The cervical spine provides structural support to the skull, enabling it to remain upright while bearing its weight. This support is crucial for maintaining posture and balance.
Facilitation of Movement
The cervical spine is highly flexible, allowing for a wide range of head and neck movements, including:
- Flexion (bending forward)
- Extension (bending backward)
- Lateral flexion (side bending)
- Rotation (turning the head side to side)
The unique structure of the atlas (C1) and axis (C2) is essential for nodding and rotational movements.
Protection of the Spinal Cord and Nerves
The cervical spine encases and protects the spinal cord as it exits the brain and travels through the vertebral foramen. It also shields the cervical spinal nerves, which pass through intervertebral foramina to innervate the upper body.
Shock Absorption
The intervertebral discs in the cervical spine absorb shock and distribute mechanical forces, reducing strain on the vertebrae during activities such as walking, running, or sudden impacts.
Pathway for Blood Supply
The transverse foramina of the cervical spine provide passage for the vertebral arteries, which supply blood to the brain and other structures of the head.
Attachment for Muscles and Ligaments
The cervical spine serves as an anchor for muscles and ligaments involved in head and neck movement, posture, and stabilization. These attachments are critical for supporting daily activities and maintaining alignment.
Clinical Significance
The cervical spine is highly susceptible to injuries and disorders due to its mobility and proximity to vital structures.
- Neck Pain and Strain: Common conditions include muscle strain, ligament sprains, and postural issues, often caused by poor ergonomics, prolonged screen time, or sudden movements.
- Cervical Disc Herniation: Herniation of intervertebral discs in the cervical spine can compress spinal nerves, causing pain, numbness, or weakness in the neck, shoulders, and arms.
- Cervical Spondylosis: Degenerative changes such as bone spurs and disc degeneration in the cervical spine are common with aging, leading to stiffness, pain, and reduced mobility.
- Whiplash Injuries: Sudden acceleration-deceleration forces, often from car accidents, can cause whiplash, resulting in neck pain, headaches, and soft tissue injury.
- Spinal Cord Compression: Conditions like cervical spinal stenosis or trauma can compress the spinal cord, potentially causing severe neurological deficits, including paralysis.
- Fractures and Dislocations: Injuries from accidents or falls can result in cervical spine fractures or dislocations, which may require surgical stabilization to prevent spinal cord damage.