Vertebral arch

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Structure and function of the vertebral column.

The vertebral arch is a ring of bone that surrounds the posterior aspect of the vertebral body of vertebrae, forming a circular opening called the vertebral foramen. When stacked together in the articulated vertebral column, the individual vertebral foramina collectively form the vertebral canal (spinal canal) which transmits the spinal cord.

The vertebral arch is composed of a pair (right and left) of pedicles and laminae. The pedicles are short, stout projections that arise from the posterolateral aspect of the vertebral body. They fuse with the broad laminae (singular: lamina), which extend posteriorly and medially from the pedicle. The right and left laminae fuse in the midline to complete the vertebral arch.

The superior and inferior aspects of each pedicle bear indentations called vertebral notches, which are best observed in the lateral view. These notches of adjoining vertebrae along with the intervertebral discs form intervertebral foramina which serve as passageways for spinal nerves.

A typical vertebral arch gives rise to seven processes: one spinous process, two transverse processes and four articular processes. 

• The spinous process projects posteroinferiorly from the junction of the laminae and is easily palpable in the midline of the back.
• The two transverse processes are posterolateral projections from the junction of the pedicle and lamina (pediculolaminar junction) on both sides.
• The four articular processes also project from the pediculolaminar junctions. They consist of two superior and two inferior processes with articular facets, which form zygapophyseal joints between adjacent vertebrae.

The vertebral arch forms the lateral and posterior walls of the vertebral foramen and protects the spinal cord. It provides attachment for deep back muscles and ligaments that support the spine while also serving as a lever to assist the action of these muscles. Additionally, the vertebral arch bears articular facets that serve as articulation sites for adjacent vertebrae.