[Function-related morphology of the intervertebral disks]

The intervertebral discs contribute to shock absorption only to a limited degree; they are important however, for efficient orientation of axial pressure transmission to the entire surface of the contiguous vertebral bodies. So long as there is sufficient distension of the nuclei pulposi, the annuli fibrosi (particularly those of the lumbar vertebral column) play a part in the ligamentous control of the motion segment. From the 20th year of life onwards the discs are completely avascular, although they show high metabolic turnover. Their water content decreases with advancing age. As early as the first decade of life, beginning in the lateral, uncovertebral zones, clefts appear in the cervical intervertebral discs. These clefts frequently progress to tears involving the whole of the intervertebral disc.