Structure
Symphyses are also known as secondary cartilaginous joints, i.e., they are made up of a fibrocartilage disc and the articular hyaline cartilages of two articulating bones. The intervertebral discs are made up of an inner nucleus pulposus and an outer, narrower lamellated annulus fibrosus, while the vertebral end plates are bi-layered hyaline cartilages. The intervertebral symphyses are thickest in the lumbar region, and thinnest in the upper thoracic region. The proportion of fibrocartilage of the intervertebral symphyses increases with age.
They are generally avascular but do receive nutrition by diffusion from vertebral bodies underneath the vertebral end plates. Venous drainage is via the external and internal vertebral venous plexuses.
Anatomical Relations
The intervertebral symphysis consists of a fibrocartilaginous intervertebral disc, a superior vertebral end plate, and a corresponding inferior vertebral end plate. The intervertebral disc is interposed between the two end plates and adheres to them between two adjacent vertebral bodies from the second cervical vertebra (C2) to the sacrum. The anterior margin of the intervertebral symphysis is attached the anterior longitudinal ligament, while its posterior margin is attached to the posterior longitudinal ligament.
Function
The intervertebral symphysis is the bonds between adjacent vertebral bodies. They maintain stability and load-bearing of the vertebral column and help to resist compression, tension, shear, bending, and torsion.
