Nimmelülid

Nimmelülid, or lumbar vertebrae, are the five vertebrae labeled L1 to L5 that form the lower part of the spinal column between the thoracic vertebrae and the sacrum. They support much of the body's weight and provide a stable axis for movement in the trunk.

Anatomy and features: Each lumbar vertebra has a large, kidney-shaped vertebral body and a relatively small vertebral foramen that is triangular in shape. The vertebral arch includes pedicles and laminae, and the spinous processes are short, thick, and directed horizontally. The transverse processes are long and slender. The superior articular facets face medially, while the inferior facets face laterally, a configuration that favors flexion and extension while limiting rotation. In addition to the standard features, lumbar vertebrae bear additive processes: mammillary processes on the posterior aspect of the superior articular processes and accessory processes at the base of the transverse processes, which serve as muscle and ligament attachment sites. There are no costal facets for rib articulation. L5 is a transitional vertebra that articulates with the sacrum and often shows unique anatomical adaptations to this junction.

Function and clinical relevance: The lumbar region bears substantial weight and enables flexion, extension, and bending to the sides, while rotations are relatively limited. The lumbar canal houses the cauda equina rather than a spinal cord, which ends at around the upper lumbar levels. Clinically, the L4–L5 and L5–S1 levels are common sites for disc herniation. Pars interarticularis defects can lead to spondylolysis and, in some cases, spondylolisthesis, particularly affecting L5. Understanding lumbar vertebrae is essential for diagnosing lower back pain and planning surgical or rehabilitative interventions.