part of part of Homo sapiens lumbar vertebra 5 zone of bone organ superior articular facet of fifth lumbar vertebra 2026-03-19T00:00:00Z A zone of bone organ forming the articular surface on the superior articular process of the fifth lumbar vertebra, with a concave, medially facing surface oriented in the sagittal plane. It articulates with the inferior articular facet of the fourth lumbar vertebra at the L4–L5 zygapophyseal joint, the most commonly affected lumbar facet joint in degenerative disease. David Osumi-Sutherland