Anat Cell Biol.  2021 Mar;54(1):65-73. 10.5115/acb.20.265.

Fetal cervical zygapophysial joint with special reference to the associated synovial tissue: a histological study using near-term human fetuses

  • 1Department of Histology and Embryology, Tokyo Dental College, Tokyo, Japan
  • 2Department of Anatomy, Division of Basic Medical Science, Tokai University School of Medicine, Kanagawa, Japan
  • 3Department of Anatomy, Wuxi School of Medicine, Jiangnan University, Wuxi, China
  • 4Department of Anatomy, Tokyo Dental College, Tokyo, Japan
  • 5Division of Internal Medicine, Jikou-kai Clinic of Home Visits, Sapporo, Japan
  • 6Department of Anatomy and Embryology, School of Medicine, Complutense University, Madrid, Spain


Human fetal cervical vertebrae are characterized by the large zygapophysial joint (ZJ) extending posteriorly. During our recent studies on regional differences in the shape, extent, and surrounding tissue of the fetal ZJ, we incidentally found a cervical-specific structure of synovial tissues. This study aimed to provide a detailed evaluation of the synovial structure using sagittal and horizontal sections of 20 near-term fetuses. The cervical ZJ consistently had a large cavity with multiple recesses at the margins and, especially at the anterior end, the recess interdigitated with or were located close to tree-like tributaries of the veins of the external vertebral plexus. In contrast to the flat and thin synovial cell lining of the recess, the venous tributary had cuboidal endothelial cells. No or few elastic fibers were identified around the ZJ. The venous-synovial complex seems to be a transient morphology at and around birth, and it may play a role in the stabilization of the growing cervical ZJ against frequent spontaneous dislocation reported radiologically in infants. The venous-synovial complex in the cervical region should be lost and replaced by elastic fibers in childhood or adolescence. However, the delayed development of the ligament flavum is also likely to occur in the lumbar ZJ in spite of no evidence of a transient venous-synovial structure. The cuboidal venous endothelium may simply represent the high proliferation rate for the growing complex.


Zygapophysial joint; Ligament; Neck; Human; Fetus
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