The vertebral bodies and components of the vertebral arches are reinforced and connected to segments above and below by many ligamentous reinforcements. Each spinous process has two main ligaments, one set of ligaments that run in-between each subsequent spinous process
– the interspinous ligament and another ligament that runs nearly the length of the column, joining tip to tip – the supraspinous ligament. From the skull to C7, the supraspinous ligament spreads out in the midsagittal plane to become a distinct sheet-like ligament called the ligamentum nuchae.
The purpose of these ligaments are to limit the amount of flexion and potentially to assist a return to neutral posture (a type of ligamentous rebound).
Ligaments between each transverse process – the intertransverse ligaments – help to limit side flexion and excessive rotation. The final ligament attaching to the vertebral arch is the ligamenta flava, a highly elastic ligament which attaches lamina to lamina. The main function of this ligament is to again resist excessive flexion and assist in the return to an anatomical position in extension.
Finally, there are two broad bands of continuous ligaments which span the length of the vertebral column, connecting vertebral bodies and intervertebraldiscs. One is located anteriorly – the anterior longitudinal ligament (ALL) and one posteriorly – the posterior longitudinal ligament (PLL). Each ligament, again, resists excessive movement – the ALL resisting extension and the PLL resisting flexion.
Besides the z-joints, a movement segment for the vertebral column is the symphysis between the vertebral bodies, otherwise known as the intervertebral disc. The disc is composed of two parts – an outer collagenous ring surrounding a central gelatinous portion. (See Image 4). The annulus fibrosus is composed of many layers of fibrocartilaginous lamellae which have the main function of limiting rotation between vertebrae. The nucleus pulposus, the jelly-like center of the disc serves to help resist compressive forces placed through the vertebrae.