The cervical spine is composed of seven vertebrae, whose shapes create the cervical lordosis.
It consists of two areas – the cervicoencephalic/cervicocranial area for the upper cervical spine (C0-C2) and the cervicobrachial area for the lower cervical spine (C3-C7) (Magee 2007). The first and second cervical vertebrae (atlas and axis respectively) differ the most from the common vertebral morphology. Their specific tasks are to bear the weight of the head and to allow the head to move in all directions (Schuenke et al. 2010). As the altas (C1) has no vertebral body of it’s own, the odontoid process (or dens) of the axis (C2) takes over this role (Magee 2007). The five lower cervical vertebrae have relatively small bodies, which are approximately square shaped viewed from above and have a large, triangular vertebral foramen. The superior and inferior surfaces of the vertebral bodies are saddle-shaped. The transverse process consists of an anterior and a posterior bar, ending laterally in anterior and posterior small tubercles. These bars enclose the transverse foramen, through which the vertebral arteries ascend from the C6 to the C1 level.
The superior surfaces on the transverse processes of the first three cervical vertebrae bear a broad, deep notch (spinal nerve sulcus), for the emerging spinal nerve of that level. The superior and inferior articular processes are broad and flat, with an inclination of approximately 45° from the horizontal plane. In contrast to the longer and thicker spinous process of the seventh cervical vertebra, the spinous processes of the third through sixth cervical vertebrae are short and bifid and not distinctly palpable through the skin (Schuenke et al. 2010).
The intervertebral disks consist of an external fibrous ring (annulus fibrosus) and a gelatinous core (nucleus pulposus). The external ring consists of an outer and inner zone. The outer zone is a fibrous
sheath that possesses high tensile strength and is made up of concentric laminae of type I collagen fibers. Joining with the inner zone the tough fibrous tissue blends with a fibrocartilaginous tissue whose type II collagen fibers are attached to the hyaline cartilage of the vertebral bodies.
The atlanto-occipital membranes are located anteriorly and posteriorly to the atlanto-occiptal joints. The anterior membrane is strengthened by the anterior longitudinal ligament. The posterior membrane replaces the ligamentum flavum between the atlas and occiput (Magee 2007) and it stretches from the posterior arch of the atlas to the posterior rim of the foramen magnum (Schuenke et al. 2010). The tectorial membrane is a broad band covering the dens and its ligaments and lies within the vertebral canal. It is a
continuation of the posterior longitudinal ligament (Magee 2007). The cruciform ligament of the atlas consists of the longitudinal fascicles and the transverse ligament of the atlas (Schuenke et al. 2010). The alar ligaments are two strong rounded cords found on each side of the upper dens passing upwards and laterally to attach on the medial sides of the occipital condyles. The alar ligaments limit flexion and rotation (Magee 2007).
The main ligaments for the cervicobrachial area are the anterior longitudinal ligament, the posterior longitudinal ligament, the ligamentum flavum and the supraspinal and interspinal ligaments (Magee 2007).