The spine serves as the central support structure of the human body, providing stability and enabling movement. Within this complex column, the neck region, known as the cervical spine, plays a significant role. It forms a flexible connection between the head and the rest of the body, allowing for a wide array of head movements. The cervical spine also acts as a protective conduit for the spinal cord.
Understanding the Cervical Spine
The cervical spine consists of seven individual bones, or vertebrae, which are stacked one upon another and designated C1 through C7 from top to bottom. This specialized section of the spine is responsible for bearing the weight of the head, which averages between 10 to 13 pounds. Beyond support, the cervical vertebrae facilitate a wide range of motions, including forward and backward bending (flexion and extension), side-to-side bending (lateral flexion), and rotation.
Between each vertebra, except for the first two, lies a soft, cushioning structure called an intervertebral disc. These discs absorb shock and contribute to the spine’s flexibility. Small openings within the cervical vertebrae, known as transverse foramina, provide a passage for vertebral arteries that supply blood to the brain, though the C7 vertebra typically does not transmit these arteries.
Locating C6 and C7
Identifying specific vertebrae in the neck can be done through palpation, or gentle touching, although precise localization requires professional medical imaging. The seventh cervical vertebra, C7, is often referred to as the “vertebra prominens” because its spinous process, a bony projection at the back of the vertebra, is usually the most prominent and easily felt at the base of the neck where it meets the shoulders. This spinous process of C7 is typically distinct, feeling like a single, non-forked bump.
To generally locate the C6 vertebra, one can identify the C7 vertebra prominens first. From this point, gently move a finger slightly upwards towards the head. The next bony projection felt just above C7 is typically the C6 vertebra.
Functions of C6 and C7
The C6 and C7 vertebrae, along with their associated nerve roots, play a role in both neck movement and the function of the upper limbs. The C6 nerve root emerges from the spinal column between the C5 and C6 vertebrae. This nerve root is involved in motor functions such as bending the elbow (biceps) and extending the wrist. It also provides sensory information to specific areas, including the thumb side of the forearm, the thumb, and the index finger.
The C7 nerve root exits the spinal column between the C6 and C7 vertebrae. This nerve root influences the ability to straighten the elbow (triceps) and extend the fingers. In terms of sensation, the C7 nerve root typically supplies the skin of the middle finger, as well as portions of the back of the arm and shoulder. Both the C6 and C7 nerve roots are part of the brachial plexus, a network of nerves that provides nerve supply to the entire upper limb.
Potential Issues Affecting C6 and C7
Due to their location and role in supporting the head and facilitating upper limb function, the C6 and C7 vertebral levels can be susceptible to various conditions. One common issue is a disc herniation, where the cushioning disc between the C6 and C7 vertebrae protrudes, potentially pressing on nearby nerve roots.
Compression or inflammation of the nerve roots at these levels can lead to a condition known as cervical radiculopathy. Symptoms can include pain, numbness, tingling, or weakness that radiates from the neck into the shoulder, arm, and hand. For example, issues affecting the C6 nerve root might cause pain or numbness in the thumb and index finger, along with weakness in the biceps or wrist. If the C7 nerve root is affected, symptoms commonly involve pain or numbness in the middle finger and weakness in the triceps or finger extensors.
Other conditions that can affect the C6 and C7 segments include spinal stenosis, which is a narrowing of the spinal canal or the openings where nerves exit, putting pressure on the spinal cord or nerve roots. Injuries, such as whiplash, can also impact these vertebrae and discs. These problems often result in general neck pain, stiffness, and reduced muscle strength, depending on the specific nerve pathways affected.