Analyzing a Typical Vertebra - dummies

Analyzing a Typical Vertebra

By David Terfera, Shereen Jegtvig

Most vertebrae are more or less the same, although they have a few differences of sizes and shapes. For example, the cervical region has two atypical vertebrae that defy the norm. A typical vertebra is made up of an anterior vertebral body and a posterior vertebral arch:

  • Vertebral body: The vertebral body is fairly large, especially in a lumbar vertebra (in other words, a vertebra found in the lower back). The vertebral bodies support the weight of your body.

  • Vertebral arch: The vertebral arch is made up of two pedicles (one on each side of the vertebra) that project posteriorly from the vertebral body. Posteriorly, each pedicle is attached to a lamina, and the two laminae merge together in the midline forming the arch. The vertebral arch and body form the vertebral foramen.

A typical vertebral arch has seven bony processes: one spinous process, two transverse processes, and four articular processes.

  • Spinous and transverse processes: These processes work as levers and serve as attachment sites for back muscles.

    • Each spinous process projects posteriorly from the point where the laminae merge on the vertebral arch.

    • The transverse processes project laterally from the pedicle/lamina junctions.

    The spinous processes are easy to find — right down the center of the back. You can usually see them, or at least you can palpate them because very little fat accumulates over the vertebral column.

  • Articular processes: These processes form joints between successive vertebrae. The superior and inferior articular processes arise from the same junctions as the transverse processes (one superior and one inferior process on each side), and each process has an articular surface called a facet. The inferior processes of each typical vertebra form synovial joints called zygapophysial joints, with the superior processes of the vertebra below.

The opening formed between the vertebral body and the vertebral arch is called the vertebral foramen, which forms the vertebral canal when all the vertebrae are stacked on top of each other. This canal is home to the spinal cord.

The pedicles of a vertebral arch have notches on their superior and inferior surfaces. These notches combine with the notches of the pedicles on adjacent vertebrae to form the intervertebral foramina, the openings between the vertebrae where the blood vessels and spinal nerves pass to and from the spinal cord and the vertebral column.

Spina bifida is a congenital birth defect in which the vertebral arch doesn’t develop properly, leaving an opening posterior to the spinal cord. A mild form, called spina bifida occulta, is hidden under the skin (but may present with a small tuft of hair over the surface) and usually has no symptoms. Spina bifida cystica is more severe, causing a visible herniation of the meninges protruding from the infant’s back. Getting an adequate intake of folate (a B vitamin) or folic acid supplements before and during pregnancy can reduce the risk of the disorder.