Cervical Spine: Characteristics
The cervical spine has a curvature of about 36 ° with an anterior convexity - called lordosis - which varies in relation to the modifications of the other spinal curves and generally becomes more marked in the elderly.
Cervical vertebrae
The cervical spine is made up of seven vertebrae, distinguishable - on the basis of some anatomical peculiarities - in an upper region (C1-C2) and in a lower region (C3-C7); for this reason the first section of the vertebral column is didactically divided into the upper cervical spine and the lower cervical spine.
, the atlas and the axis are very different from the other vertebrae of the spine. The atlas is a bony ring consisting of an anterior arch, a posterior arch and two lateral masses (it has no vertebral body and spinous process). Each of these two bone massifs has an upper and a lower articular facet, which they articulate respectively with the occipital condyles and with the axis. The latter consists of a vertebral body and a bifid spinous process such as the underlying vertebrae, from which it differs for the large bony apophysis that departs from the anterior part of its vertebral body (odontoid, odontoid process or axis of the tooth) ; this bone segment, which is nothing more than the residue of the body of the atlas, is articulated with the anterior arch of the atlas itself, constituting the axis around which C1 can turn in the rotational movements of the head.
The atlas owes its name to the mythological character of the same name who was believed to carry the weight of the world on his shoulders, just as the vertebra does with the "globe" of his head.
The atlanto occipital joint allows moderate lateral flexion movements, 10 degrees of flexion and 25 degrees of extension; a few degrees in the same directions are also allowed by the joint relationships between C1 and C2. D "on the other hand, however, atlas and axis provide the main contribution to the rotation of the cervical spine, which they support for 45 ° in both directions.
The intervertebral disc is not interposed between C1 and C2 and excessive movement is limited by the ligaments and joint capsule.
The mobility of the upper cervical spine is essential to maintain the correct alignment of the sense organs located in the head (sight and hearing).
The muscles that participate in the movement of the upper segment of the cervical spine are shown in the following table.
Compared to the upper cervical spine, this region of the spine specializes no longer in rotation, but in anterior, posterior (extension) and lateral flexion. The latter is mainly entrusted to the upper section (C3-C4 and C4-C5), while the flexion - equal to about 10 degrees per segment - is maximum at the level of C4-C5 and C5-C6.
