The lumbar vertebrae (Latin: vertebrae lumbales) form the skeletal support for the posterior abdominal wall. There are five lumbar vertebrae (L1 - L5) forming the lumbar part of the vertebral column that continues inferior from the thoracic part. The lumbar vertebrae differ from other vertebrae by their large size and that they do not have facets for articulations with ribs.
Similarly to other vertebrae, each lumbar vertebrae has a vertebral body and a vertebral arch. The vertebral arch is formed by a pair of pedicles and a pair of laminae, it encloses the vertebral foramen and supports seven processes.
The body of a typical lumbar vertebra is large and cylindrical, typically, wider from side to side than from front to back.
The pedicles of the lumbar vertebrae are directed backward from the upper part of the vertebral body. The pedicles significantly increase in width and in angulation in the axial plane from upper lumbar to lower lumbar vertebrae.
The laminae are typically broad and short. These elements form the posterior portion of the vertebral arch, and they connect the spinal process with the pedicles of each vertebra.
The vertebral foramen is triangular when viewed from above. It is larger in the lumbar vertebrae than the thoracic vertebrae but smaller than in the cervical vertebrae. The vertebral foramina create the spinal canal, which surrounds and protects the spinal cord.
The spinal process of the typical lumbar vertebra is thick, broad, and somewhat quadrilateral. It projects backward and ends with a thick, uneven border.
The superior and inferior articular processes of the lumbar vertebrae are usually well-defined. They project upward and downward, respectively, arising from the junctions of pedicles and laminae.
The transverse processes of the lumbar vertebrae are usually thin and long, except for the fifth lumbar vertebra, which has massive and somewhat cone-shaped transverse processes for attachment of iliolumbar ligaments. These are ligaments that connect the transverse processes to the pelvic bones.
Three portions can be seen on the transverse processes of the lower lumbar vertebrae: a costiform process, a mammillary process, and an accessory process. The lateral or costiform process is directed laterally, the mammillary process - superiorly (cranially), while the accessory process - inferiorly (caudally).