Vertebral Structures

Printer Friendly Version

The outer shell of a vertebra is made of cortical bone.  Cortical bone is dense, solid and strong.  Inside each vertebra is cancellous bone, which is weaker than cortical bone and consists of loosely knit structures that resemble honeycomb.  Bone marrow, which forms red blood cells and some types of white blood cells, is found within the cavities of cancellous bone.  Vertebrae consist of the following common elements:

Vertebral Body: The largest part of a vertebra.  If looked at from above, it generally is almost oval shaped.  From the side, it is shaped like an hourglass; thicker at the ends and thinner in the middle.  The body is covered with strong cortical bone, with cancellous bone within.

Pedicles: Two short processes made of strong cortical bone that project off the back of the vertebral body.

Laminae: Two relatively flat plates of bone extend from either side of each pedicle join in the midline.

Processes: There are three types of processes: (1) articular, (2) transverse and (3) spinous. The processes serve as connection points for ligaments and tendons.

• Four articular processes join with other vertebral articular processes to form the facet joints.  Facet joints and the intervertebral discs, allow for spinal motion.

• Transverse processes project outward off the back of the spine where the laminae and pedicles meet.

• Spinous processes extend from the back of each vertebrae where two laminae join.  The spinous processes act as levers to control vertebral motion.

Endplates:  Endplates coat the top (superior) and bottom (inferior) parts of each vertebrae.  Endplates blend into the intervertebral disc to help secure it in place.

Intervertebral Foramen: Each pedicle has a small notch on its upper surface, and a deep notch on the bottom surface. When the vertebrae are stacked on top of each other the pedicle notches form an area called the intervertebral foramen. This area is of critical importance, as the nerve roots exit from the spinal cord through these areas to the rest of the body.

Facet Joints: The spine's joints are the Facet Joints.  Each join is located at the back of the spine.  Facet joints enable the spine to bend, twist, and extend.  Furthermore, they restrict excessive movement such as hyperextension (bending backward too far) and hyperflexion (bending forward too far).