Precise Anatomical Position
The C6 and C7 vertebrae are located within the cervical spine, the upper portion of the vertebral column in the neck. The cervical spine consists of seven vertebrae, numbered C1 through C7. Specifically, C6 is the sixth cervical vertebra, positioned below C5 and above C7.
The C7 vertebra is the seventh and final bone in the cervical series, situated just above the first thoracic vertebra (T1). These two vertebrae are found at the base of the neck, near the junction with the upper back. The C7 vertebra is often distinguishable as the most prominent vertebral bone felt at the lower part of the neck, especially when bending the head forward.
These vertebrae are stacked precisely, forming a protective bony canal that encases the spinal cord. They are separated by intervertebral discs, which act as shock absorbers and facilitate movement.
Role in Spinal Function
The C6 and C7 vertebrae support the weight of the head, which averages between 10 to 12 pounds in adults. This supportive function helps maintain upright posture and balance. Their structural design, along with other cervical vertebrae, contributes to the natural forward curve of the neck, known as the cervical lordosis.
These vertebrae facilitate head and neck movements. They enable actions such as flexion (bending the head forward), extension (bending the head backward), lateral bending (tilting the head side to side), and rotation (turning the head left and right). The intervertebral discs and facet joints between C6 and C7 enable these motions, allowing smooth articulation.
Beyond movement, the C6 and C7 vertebrae offer critical protection to the spinal cord as it descends from the brain. The bony arches of these vertebrae form a shield around this delicate nervous tissue. Their stability supports the spinal column, ensuring continuous transmission of nerve signals.
Nerve Connections and Common Symptoms
Spinal nerves emerge from the spinal cord at each vertebral level. For C6 and C7, these are the C6 and C7 nerve roots. The C6 nerve root exits the spinal canal above the C6 vertebra, while the C7 nerve root exits above the C7 vertebra. These nerve roots then join with others to form the brachial plexus, a network of nerves that supplies the shoulder, arm, and hand.
The C6 nerve root controls muscles for wrist extension and elbow flexion, such as the biceps. It also carries sensory information from the thumb, index finger, and parts of the forearm. Compression or irritation of the C6 nerve root can lead to pain radiating down the arm, numbness in the thumb and index finger, or weakness in the biceps muscle.
Similarly, the C7 nerve root controls muscles for elbow extension, such as the triceps, and wrist flexion. This nerve root also conveys sensation from the middle finger and parts of the hand and forearm. If the C7 nerve root becomes compressed, individuals may experience pain that travels down the arm to the middle finger, numbness or tingling in the middle finger, or weakness in the triceps muscle.