Each functional spinal unit (FSU) consists of two adjacent vertebrae and the intervertebral disc. In general, FSU movement is small; large overall spinal movements are achieved with small contributions from many FSUs.
The vertebra, classified as an irregular bone because of its complex shape, has several important anatomical features, including the vertebral body, spinous process, transverse process, lamina, pedicle, and facet joints. The vertebral body is an oval-shaped structure that supports axial forces and provides a seat for the intervertebral disc. The spinous process and the transverse process provide attachment points for muscles and ligaments of the spine. The lamina is the flat section of the vertebra that forms the roof of the spinal canal. When the spinal canal becomes compressed, a laminectomy surgery may be performed to decompress the spinal cord. The pedicle is a region of the vertebra that connects the lamina to the vertebral body. It is a location where pedicle screws are placed during spinal fusion surgery. Facet joints are small synovial joints used to guide and limit movement of the spinal column.
