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Lumbar vertebra 4
Other Terms: L4 vertebra
These large vertebrae are recognizable by their lack of transverse foramina or costal facets. They have large block-like bodies with kidney-shaped articular surfaces. The short, thick pedicles arise from the superoposterior portion of the block-like body. Above the pedicle is a shallow notch, while below the pedicle is a deep notch. Short, thick laminae unite to support a strong, quadrilateral spine. The laminae are shorter in the vertical plane than the body, leaving spaces between adjacent articulated vertebrae. The articular processes are large with weakly curved surfaces whose major axis is in the sagittal plane. The transverse process is technically a misnomer. In reality, this is the costal process and is homologous with the ribs, which sometimes develop separately forming lumbar ribs. The true transverse processes form from the posteriorly placed accessory and mamillary processes.
The word lumbar comes from the Latin term lumbus for loin. It is an ancient term, first used by Claudius Galen in the 2nd Century. The word vertebra is an old Latin term that meant a joint or something to be turned. It arises from the Latin verto meaning to turn. In A.D. 30 Celsus used the word to designate any joint. It was only in later years that the bone arrived at its present meaning.
This vertebra articulates with two other vertebrae: the superjacent and subjacent vertebrae. Six articular surfaces unite each typical vertebra. The two superior articular facets articulate with the corresponding inferior articular facets of the adjacent vertebra and the superior and inferior surfaces of the vertebral bodies form an articulation via the intervertebral disc of cartilage.
Five cartilaginous centers arise as anlage to all vertebrae and ribs. One center forms the body, two anterolateral centers form the costal elements, two posterolateral centers form the vertebral arch elements. In this vertebra the body anlage begins to ossify during the third intrauterine month. At this time the ossification centers for the costal and arch anlagen appear and merge into paired lateral centers. At birth, the three ossifying centers are still separate. The two laminae unite during the third year, but they do not join the body until the sixth year. This fusion typically begins cranially and moves caudally. Secondary centers appear at the tips of the transverse, accessory, mamillary, and spinous processes and on the inferior and superior surfaces of the bodies. These secondary centers appear at puberty and typically fuse in the late teen years, the epiphyseal rings and spines being most variable in length of fusion.