Each individual vertebra has unique features depending on the region in which it is found. Every vertebra, regardless of location, has three basic functional parts: (1) the drum-shaped vertebral body, designed to bear weight and withstand compression or loading; (2) the posterior (backside) arch, made of the lamina, pedicles and facet joints; and (3) the transverse processes, to which muscles attach.
The vertebral body is composed of hard cortical bone on the outside and less dense cancellous bone on the inside. The top and bottom of the vertebral body are called the end plates. The intervertebral disc, sandwiched between two vertebral bodies, is attached to the end plates. Changes in the disc may be accompanied by changes in the end plates.
The pedicle is a paired, strong, tubular bony structure made of hard cortical bone on the outside and cancellous bone on the inside. Each pedicle comes out of the side of the vertebral body and projects to the back. Pedicles act as the lateral (side) walls of the bony spinal canal that protects the spinal cord and cauda equina, or nerve roots, in the lumbar region. There is also a space created between the facet joints and pedicles of one vertebral body and the next, called the intervertebral foramen, through which the spinal nerves branch out to the rest of your body.
The lamina are shingle-like plates of bone coming from the pedicles to arch over the nerves and join at the midline. The lamina are shorter than the vertebral bodies so that there is a gap between any two laminae, bridged by soft tissue called the ligamentum flavum. This provides additional protection for the nerves that lie underneath it. Together, the lamina and pedicles form the vertebral arch.
As the lamina come together at the back of the spinal column, they join to form the spinous process, the bony part of the spine that you can feel at the midline when you rub your back. There is an interspinous ligament that runs between the spinous processes of the vertebrae and a supraspinous ligament that runs on top of them from the cervical region to the sacrum.
Each vertebral body has two articular processes at the top and bottom where the lamina and pedicle meet. These articular processes create a joint, called the facet joint, between the stacked vertebral bodies. There is a facet joint on each side of the vertebral body. The facet joint typically lies behind the spinal nerves as they emerge from the central spinal canal. The surfaces of the facet joint are capped with cartilage and the joint is contained in a capsule lined by synovium, much like the knee joint. The two facet joints and the intervertebral disc at each level allow for motion between the vertebral bodies.
The typical vertebral body has two transverse processes, or lateral projections, one on each side. These projections serve as points of attachment for muscles and ligaments in the spine. In the cervical spine, the transverse processes each have a foramen or canal through which the vertebral artery and vein travel. The intertransverse ligaments connect the transverse processes of the vertebrae on each side of the spinal column.
In the lumbar spine, identification of the pars interartcularis is important because it is the site of pathology related to spondylolisthesis, or "slipped vertebra." This is another paired structure on the back side of the spine and it links the pedicle, transverse process, lamina and articular facets on each side of the vertebrae.