The cervical spine consists of seven vertebrae and is located at the base of the skull. Its function is to support the skull, enabling head movements back and forth, and from side to side, as well as protecting the spinal cord. The upper section of the cervical spine consists of the first cervical vertebrae (C1) and the second cervical vertebrae (C2). The lower section consists of the third cervical vertebrae (C3) through seventh cervical vertebrae (C7). These spinal bones attach to the thoracic spine and work together to support the head.

The fifth cervical vertebra (C5) is the fifth vertebra from the top of the column. The C5 is a significant landmark when determining the likely consequences of trauma to the neck and spinal column. If the spinal cord injury is at or above the C5, the person may be unable to breathe, since the spinal cord nerves located between the third and fifth cervical vertebrae control respiration. Even if death by asphyxiation is avoided by emergency measures, the person will likely be left as a quadriplegic. If the injury is below the C5, the likely outcome is that the person will be a paraplegic. If a spinal injury is suspected, do not move the affected person unless doing so is necessary in order to escape an immediate deadly threat, such as a burning house.