Our necks are our spines continuing above shoulder level so that our head can be supported and facilitated in its job. The neck is beautifully designed and engineered and performs its highly complex functions automatically without us having to give them any thought. Our heads are very heavy and placed on top of the lever which is the neck, however we can move them or stop moving them very quickly, positioning them at a very specific point within the large ranges of movement the neck can perform. The ears and eyes, some of our most vital organs of sensory input, are placed on the head and the neck has to serve their needs.
The cervical spine is a complicated structure made up of ligaments, discs, joints, muscles and bones. What are missing from this description are the vitally important and widespread nets of nerve fibres which clothe the spinal structures here. Nerve functions include the control of movement, the transmission of sensory information for biofeedback and balance and the control of circulation and other reflex responses. The neck has a difficult job to do as the very large ranges of movement it needs to provide are at odds with its precision and delicate control.
When the neck starts to complain for the first time it is almost always via symptoms referred to as mechanical, symptoms which reflect the stresses and strains which are put on the structures involved. Suffering from pain and loss of joint movement are common complaints, with a series of other complaints including mental stresses, loss of muscle power, visual disturbance, unsteadiness and headaches. By settling the cervical structures down towards normal the physiotherapist can help the various other related symptoms settle down too.
The neck is an exceptionally mobile part of the body and in part that is due to the thickness of the cervical discs, which are thick when compared to the thickness of the cervical vertebrae. The thicker the disc the more movement the segment can perform. The facet joints are also larger in comparison those in the thoracic and lumbar spine, allowing large facet-like flat surfaces for gliding movement under close control. They allow much greater ranges of movement than in other areas of the body where stability may be more important.
The upper two vertebrae, the atlas and the axis, are very different from the remaining five cervical vertebrae, and they are specialised to serve the function of support and movement for the skull. The junction between the atlas (the C1 vertebra) and the axis (the C2 vertebra) is endowed with a rotatory type of structure, making up a significant proportion of all the rotation which occurs in the neck. The movements of the neck are very great, including flexion, extension, rotations and side flexions, allowing us to place our faces in any combination of degrees and position to perform many functional activities.
Our thoracic spine is the basic foundation for the stability and mobility of the cervical spine. It facilitates the mobility of the neck and without this the neck would be subject to greater stresses where it meets the skull and the relatively stiffer thoracic spine. The neck sticks up narrowly to the skull with the muscles around it acting like wire ropes of a, holding it steady so it does not shake. Since the head is heavy and mostly in front of the centre of gravity this job is difficult and they must work hard to control balance of the head, which needs to be stable for our sense organs.
The neck flexor muscles, situated anterior to the neck, do not have a lot of work to do as they only really function strongly in getting up from lying down. It is a different story for the extensor muscles behind the neck as they have the job of keeping the head up for the whole day without tiring, only showing their function when we get tired in a train when sitting and our head flops forward as the extensors turn off. While balancing the forces applied to the neck and maintaining posture is their key function they also produce levels of compressive forces.